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1. Modeling the formation of Menrva impact crater on Titan: Implications for habitability

Author: Brandon C. Johnson, Michael Malaska, Elizabeth A. Silber, E. E. Bjonnes, R. M. C. Lopes, Steve Vance, A. Solomonidou, Jason M. Soderblom, Christophe Sotin, and A. P. Crósta
Subjects: geography, geography.geographical_feature_category, Bedrock, Astronomy and Astrophysics, Context (language use), Astrobiology, Atmosphere, symbols.namesake, Impact crater, Space and Planetary Science, Hypervelocity, symbols, Erosion, Titan (rocket family), Subsurface flow, Geology
Abstract: Titan is unique in the solar system: it is an ocean world, an icy world, an organic world, and has a dense atmosphere. It is a geologically active world as well, with ongoing exogenic processes, such as rainfall, sediment transportation and deposition, erosion, and possible endogenic processes, such as tectonism and cryovolcanism. This combination of an organic and an ocean world makes Titan a prime target for astrobiological research, as biosignatures may be present in its surface, in impact melt deposits and in cryovolcanic flows, as well as in deep ice and water ocean underneath the outer ice shell. Impact craters are important sites in this context, as they may have allowed an exchange of materials between Titan's layers, in particular between the surface, composed of organic sediments over icy bedrock, and the subsurface ocean. It is also possible that impacts may have favored the advance of prebiotic chemical reactions themselves, by providing thermal energy that would allow these reactions to proceed. To investigate possible exchange pathways between the subsurface water ocean and the organic-rich surface, we modeled the formation of the largest crater on Titan, Menrva, with a diameter of ca. 425 km. The premise is that, given a large enough impact event, the resulting crater could breach into Titan's ice shell and reach the subsurface ocean, creating pathways connecting the surface and the ocean. Materials from the deep subsurface ocean, including salts and potential biosignatures of putative subsurface biota, could be transported to the surface. Likewise, atmospherically derived organic surface materials could be directly inserted into the ocean, where they could undergo aqueous hydrolysis to form potential astrobiological building blocks, such as amino acids. To study the formation of a Menrva-like impact crater, we staged numerical simulations using the iSALE-2D shock physics code. We varied assumed ice shell thickness from 50 to 125 km and assumed thermal structure over a range consistent with geophysical data. We analyze the implications and potential contributions of impact cratering as a process that can facilitate the exchange of surface organics with liquid water. Our findings indicate that melt and partial melt of ice took place in the central zone, reaching ca. 65 km depth and ca. 60 km away from the center of the structure. Furthermore, a volume of ca. 102 km3 of ocean water could be traced to depths as shallow as 10 km. These results highlight the potential for a significant exchange of materials from the surface (organics and ice) and the subsurface (water ocean), particularly in the crater's central area. Our studies suggest that large hypervelocity impacts are a viable and likely key mechanism to create pathways between the underground water ocean and Titan's organic-rich surface layer and atmosphere.
Published: 2021

2. Nitrogen Exsolution and Bubble Formation in Titan's Lakes

Author: Jason M. Soderblom, K. Farnsworth, Jordan K. Steckloff, Vincent Chevrier, Dustin Laxton, Alejandro Soto, and S. Singh
Subjects: symbols.namesake, Geophysics, chemistry, symbols, General Earth and Planetary Sciences, Environmental science, chemistry.chemical_element, Liquid bubble, Titan (rocket family), Nitrogen, Astrobiology
Published: 2019
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3. Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander

Author: Simon Stähler, E. R. Stofan, Kevin P. Hand, C. D. Neish, William B. Brinckerhoff, Colin Wilson, Ralph D. Lorenz, Scot Rafkin, R. A. Yingst, Tetsuya Tokano, Kris Zacny, Jani Radebaugh, Christopher P. McKay, Patrick N. Peplowski, Alexander Hayes, Erich Karkoschka, Juan M. Lora, Jorge I. Nunez, Jason W. Barnes, Claire E. Newman, Melissa G. Trainer, Alice Le Gall, A. M. Parsons, Caroline Freissinet, Mark P. Panning, Lynnae C. Quick, David J. Lawrence, Carolyn M. Ernst, Cyril Szopa, Thomas P. Wagner, Jeffrey R. Johnson, Hiroaki Shiraishi, R. S. Miller, Kristin S. Sotzen, Sarah M. Hörst, Shannon MacKenzie, Elizabeth P. Turtle, Morgan L. Cable, Scott L. Murchie, Jason M. Soderblom, Angela Stickle, Department of Physics [Moscow,USA], University of Idaho [Moscow, USA], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), NASA Goddard Space Flight Center (GSFC), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Astronomy [Ithaca], Cornell University [New York], Morton K. Blaustein Department of Earth and Planetary Sciences [Baltimore], Johns Hopkins University (JHU), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Department of Earth and Planetary Sciences [New Haven], Yale University [New Haven], NASA Ames Research Center (ARC), Planetary Science Institute [Tucson] (PSI), Department of Earth Sciences [London, ON], University of Western Ontario (UWO), Aeolis Research, Department of Geological Sciences [BYU], Brigham Young University (BYU), Southwest Research Institute [Boulder] (SwRI), Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), Department of Earth and Planetary Sciences [Cambridge, USA] (EPS), Harvard University [Cambridge], Smithsonian National Air and Space Museum, Smithsonian Institution, Institut für Geophysik und Meteorologie [Köln], Universität zu Köln, NASA Headquarters, Department of Atmospheric, Oceanic and Planetary Physics [Oxford] (AOPP), University of Oxford [Oxford], Honeybee Robotics Ltd, Institute of Geophysics [ETH Zürich], Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), and Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)
Subjects: Aquifer, 01 natural sciences, Mantle (geology), Astrobiology, Pre-biotic astrochemistry, 03 medical and health sciences, symbols.namesake, Extant taxon, Impact crater, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Planetary surfaces, 14. Life underwater, 010303 astronomy & astrophysics, 030304 developmental biology, 0303 health sciences, geography, geography.geographical_feature_category, Habitability, Astronomy and Astrophysics, Prebiotic chemistry, Geophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], symbols, Water ice, Titan (rocket family), Titan, Planetary atmospheres
Abstract: NASA’s Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonfly's science themes include investigation of Titan’s prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based “life as we know it” (as might occur in the interior mantle ocean, potential cryovolcanic flows, and/or impact melt deposits) and potential “life, but not as we know it” that might use liquid hydrocarbons as a solvent (within Titan’s lakes, seas, and/or aquifers). Consideration of both of these solvents simultaneously led to our initial landing site in Titan’s equatorial dunes and interdunes to sample organic sediments and water ice, respectively. Ultimately, Dragonfly's traverse target is the 80 km diameter Selk Crater, at 7° N, where we seek previously liquid water that has mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan’s tropical deserts in the global methane cycle. We will investigate the processes and processing rates that modify Titan’s surface geology and constrain how and where organics and liquid water can mix on and within Titan. Importantly, we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonfly, along with Perseverance, is the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976.
Published: 2021
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4. New Frontiers Titan Orbiter

Author: Nicholas A. Lombardo, Shawn Brueshaber, Kerry Ramirez, Shannon MacKenzie, Marc Neveu, Alfred S. McEwen, Thomas Cornet, R. T. Desai, Jason D. Hofgartner, Ella Sciamma-O'Brien, Elizabeth P. Turtle, Ed Sittler, Thomas W. Momary, Jani Radebaugh, Stéphane Le Mouélic, Steve Vance, Ari H.D. Koeppel, Paolo Tortora, Ralph D. Lorenz, Patrice Coll, Miriam Rengel, D. Nna-Mvondo, Paul Corlies, Christopher P. McKay, Nicholas A Teanby, L. R. Schurmeier, Tilmann Denk, Gregory A. Neumann, Mark Gurwell, Jason M. Soderblom, Jennifer Hanley, Ajay B. Limaye, Mathieu G.A. Lapotre, Anezina Solomonidou, Daniel Cordier, Sarah A. Fagents, Lori K. Fenton, Conor A. Nixon, Sébastien Lebonnois, Samuel Birch, Chloé Daudon, Sébastien Rodriguez, Michael Heslar, Juan M. Lora, Liliana Lefticariu, Ross A. Beyer, Leonardo Regoli, Chuanfei Dong, E. C. Czaplinski, Farid Salama, Paul O. Hayne, Michael Malaska, A. D. Maue, R. N. Schindhelm, Athena Coustenis, Emilie Royer, Alexander G. Hayes, Catherine D. Neish, Jason W. Barnes, Sandrine Vinatier, Jordan Stekloff, Andrew J. Coates, Erich Karkoschka, Mark Elowitz, J. Michael Battalio, Timothy A. Goudge, Sarah M. Hörst, D. M. Burr, Morgan L. Cable, Shiblee R. Barua, Tuan H. Vu, Rosaly M. C. Lopes, and Rajani D. Dhingra
Subjects: Orbiter, symbols.namesake, law, spacecraft, symbols, decadal survey, White paper, Titan (rocket family), Titan, Geology, Astrobiology, law.invention
Published: 2021

5. The Science Case for a Titan Flagship-class Orbiter with Probes

Author: Conor A. Nixon, Jason M. Soderblom, Xi Zhang, Athena Coustenis, Sébastien Rodriguez, Jani Radebaugh, Jason W. Barnes, Ralph D. Lorenz, Andrew D. Ashton, Mathieu Choukroun, Kathleen Mandt, Adrienn Luspay-Kuti, Elizabeth P. Turtle, Juan M. Lora, Ashley Schoenfeld, Alexander C. Gagnon, Niklas J. T. Edberg, Louis-Alexandre Couston, Stéphane Le Mouélic, Marco Mastrogiuseppe, Gabriel Tobie, Véronique Vuitton, Sandrine Vinatier, Erwan Mazarico, Nathalie Carrasco, X. Sun, Taylor Perron, Darci Snowden, Orenthal J. Tucker, Melissa G. Trainer, Marc Neveu, Luciano Iess, Anezina Solomonidou, Farid Salama, Michael Malaska, Jason D. Hofgartner, Rosaly M. C. Lopes, Nicholas A Teanby, James B. Abshire, Coustenis, Athena, NASA Goddard Space Flight Center (GSFC), Woods Hole Oceanographic Institution (WHOI), University of Idaho [Moscow, USA], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Swedish Institute of Space Physics [Uppsala] (IRF), and University of Washington [Seattle]
Subjects: Solar System, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 7. Clean energy, Astrobiology, law.invention, Atmosphere, symbols.namesake, Orbiter, Planet, law, Saturn, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics::Atmospheric and Oceanic Physics, Earth and Planetary Astrophysics (astro-ph.EP), Spacecraft, business.industry, Planetary science, 13. Climate action, Physics::Space Physics, symbols, Environmental science, Astrophysics::Earth and Planetary Astrophysics, Titan (rocket family), business, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: We outline a flagship-class mission concept focused on studying Titan as a global system, with particular emphasis on the polar regions. Investigating Titan from the unique standpoint of a polar orbit would enable comprehensive global maps to uncover the physics and chemistry of the atmosphere, and the topography and geophysical environment of the surface and subsurface. The mission includes two key elements: (1) an orbiter spacecraft, which also acts as a data relay, and (2) one or more small probes to directly investigate Titan's seas and make the first direct measurements of their liquid composition and physical environment. The orbiter would carry a sophisticated remote sensing payload, including a novel topographic lidar, a long-wavelength surface-penetrating radar, a sub-millimeter sounder for winds and for mesospheric/thermospheric composition, and a camera and near-infrared spectrometer. An instrument suite to analyze particles and fields would include a mass spectrometer to focus on the interactions between Titan's escaping upper atmosphere and the solar wind and Saturnian magnetosphere. The orbiter would enter a stable polar orbit around 1500 to 1800 km, from which vantage point it would make global maps of the atmosphere and surface. One or more probes, released from the orbiter, would investigate Titan's seas in situ, including possible differences in composition between higher and lower latitude seas, as well as the atmosphere during the parachute descent. The number of probes, as well as the instrument complement on the orbiter and probe, remain to be finalized during a mission study that we recommend to NASA as part of the NRC Decadal Survey for Planetary Science now underway, with the goal of an overall mission cost in the "small flagship" category of ~$2 bn. International partnerships, similar to Cassini-Huygens, may also be included for consideration., 13 pages, white paper submitted to the NRC Decadal Survey for Planetary Science and Astrobiology
Published: 2020

6. A new digital terrain model of the Huygens landing site on Saturn's largest moon, Titan

Author: C. Daudon, B. Grieger, R. L. Kirk, Jason M. Soderblom, Elpitha Howington-Kraus, A. Escalante López, Sebastien Rodriguez, Antoine Lucas, Erich Karkoschka, S. Jacquemoud, Marithelma Costa, J. T. Perron, Institut de Physique du Globe de Paris (IPGP), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: 010504 meteorology & atmospheric sciences, lcsh:Astronomy, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Environmental Science (miscellaneous), 01 natural sciences, Astrobiology, lcsh:QB1-991, symbols.namesake, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, topography, 0103 physical sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Digital elevation model, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 010303 astronomy & astrophysics, DISR, 0105 earth and related environmental sciences, lcsh:QE1-996.5, rivers, DTM, lcsh:Geology, 13. Climate action, Huygens, symbols, General Earth and Planetary Sciences, Titan, Titan (rocket family), Geology
Abstract: International audience; A new digital terrain model of the Huygens landing 1 site on Saturn's largest moon • We create a new digital terrain model (DTM) of the Huygens landing site that 14 offers the best available resolution of river valleys on Titan. 15 • The complexity of the data set requires a tailor-made reconstruction procedure 16 that is detailed. 17 • The workflow uses reprocessed Huygens/DISR images and an automated shape-18 from-motion algorithm to improve an earlier DTM. Abstract 20 River valleys have been observed on Titan at all latitudes by the Cassini-Huygens 21 mission. Just like water on Earth, liquid methane carves into the substrate to form a com-22 plex network of rivers, particularly stunning in the images acquired near the equator by 23 the Huygens probe. To better understand the processes at work that form these land-24 scapes, one needs an accurate digital terrain model (DTM) of this region. The first and 25 to date the only existing DTM of the Huygens landing site was produced by the United 26 States Geological Survey (USGS) from high-resolution images acquired by the DISR (De-27 scent Imager/Spectral Radiometer) cameras onboard the Huygens probe and using the 28 SOCET SET photogrammetric software. However, this DTM displays inconsistencies, 29 primarily due to non optimal viewing geometries and to the poor quality of the origi-30 nal data, unsuitable for photogrammetric reconstruction. We investigate a new approach, 31 benefiting from a recent reprocessing of the DISR images correcting both the radiomet-32 ric and geometric distortions. For the DTM reconstruction, we use MicMac, a photogram-33 metry software based on automatic open-source shape-from-motion algorithms. To over-34 come challenges such as data quality and image complexity (unusual geometric config-35 uration), we developed a specific pipeline that we detailed and documented in this ar-36 ticle. In particular, we take advantage of geomorphic considerations to assess ambigu-37 ity on the internal calibration and the global orientation of the stereo model. Besides the 38 novelty in this approach, the resulting DTM obtained offers the best spatial sampling 39 of Titan's surface available and a significant improvement over the previous results. 40
Published: 2020
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7. Tracking Short-term Variations in the Haze Distribution of Titan’s Atmosphere with SINFONI VLT

Author: Juan M. Lora, Fiona Nichols-Fleming, Alexander G. Hayes, Jason M. Soderblom, Patricio Rojo, Paul Corlies, Sebastien Rodriguez, Máté Ádámkovics, and Elizabeth P. Turtle
Subjects: Haze, Distribution (number theory), Astronomy and Astrophysics, Tracking (particle physics), Atmospheric sciences, Term (time), Atmosphere, symbols.namesake, Geophysics, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), symbols, Environmental science, Titan (rocket family)
Abstract: While it has long been known that Titan’s haze and atmosphere are dynamic on seasonal timescales, recent results have revealed that they also exhibit significant subseasonal variations. Here, we report on observations of Titan acquired over an eight-month period between 2014 April and 2015 March with the Spectrograph for Integral Field Observations in the Near Infrared instrument on the Very Large Telescope using adaptive optics. These observations have an average five-day cadence, permitting interrogation of the short-period variability of Titan’s atmosphere. Disk-resolved spectra in the H and K bands (1.4–2.4 μm) were analyzed with the PyDISORT radiative transfer model to determine the spatial distribution and variation of stratospheric haze opacity over subseasonal timescales. We observed a uniform decrease in haze opacity at 20°N and an increase in haze opacity at 250–300°E and ∼40°N over the span of our observations. Globally, we found variations on the order of 5%–10% on timescales of weeks, as well as a steady, global increase in the amount of haze over timescales of months. The observed variations in haze opacity over the short timescales of our observations were of similar magnitude to long-period variations attributed to seasonal variation, suggesting rapid dynamical processes that may take part in the distribution of hazes in Titan’s atmosphere.
Published: 2021
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8. Titan as Revealed by the Cassini Radar

Author: Federico Tosi, L. A. Soderblom, Charles Elachi, G. Mitri, Zhimeng Zhang, Alexander G. Hayes, S. D. Wall, Jason M. Soderblom, P. Paillou, Elizabeth P. Turtle, Richard West, R. L. Kirk, Gian Gabriele Ori, Tom G. Farr, Howard A. Zebker, Claudia Notarnicola, Paul Corlies, M. Mastroguiseppe, Jason W. Barnes, Antoine Lucas, K. L. Mitchell, Jason D. Hofgartner, Bryan Stiles, Athena Coustenis, Valerio Poggiali, A. Solomonidou, Cyril Grima, Roberto Orosei, O. Karatekin, E. R. Stofan, Jani Radebaugh, Spd Birch, Rmc Lopes, Domenico Casarano, A. LeGall, P Encrenaz, Michael Malaska, Charles A. Wood, Flora Paganelli, Douglas J. Hemingway, Daniele Riccio, Sebastien Rodriguez, Catherine D. Neish, M. A. Janssen, R. D. Lorenz, Paul Ries, Jonathan I. Lunine, Ashley Schoenfeld, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Department of Astronomy [Ithaca], Cornell University, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Astrogeology Science Center [Flagstaff], United States Geological Survey [Reston] (USGS), University of Arizona, Lunar and Planetary Laboratory [Tucson] (LPL), Università degli Studi di Roma 'La Sapienza' [Rome], Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Florida Institute of Technology [Melbourne], Institut de génétique humaine (IGH), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Service de cardiologie [Hôpital Nord - APHM], Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)- Hôpital Nord [CHU - APHM], Observatoire Bordeaux, Université Sciences et Technologies - Bordeaux 1, Department of Geological Sciences [BYU], Brigham Young University (BYU), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, Proxemy Research Inc, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Wheeling Jesuit University, Department of Electrical Engineering [Stanford], Stanford University [Stanford], Istituto di Ricerca per la Protezione Idrogeologica [Bari] (IRPI), Consiglio Nazionale delle Ricerche [Roma] (CNR), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Swedish Institute of Space Physics [Uppsala] (IRF), Miller Institute for Basic Research in Science, University of California [Berkeley], Royal Observatory of Belgium [Brussels], Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), International Research School of Planetary Sciences [Pescara] (IRSPS), Università degli studi 'G. d'Annunzio' Chieti-Pescara [Chieti-Pescara] (Ud'A), Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [London, ON], University of Western Ontario (UWO), Institute for Earth Observation [Bolzano], EURAC Research, Search for Extraterrestrial Intelligence Institute (SETI), ASP 2019, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Smithsonian National Air and Space Museum, Smithsonian Institution, Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Planetary Science Institute [Tucson] (PSI), Department of Physics [Moscow,USA], University of Idaho [Moscow, USA], Istituto di Ricerca per la Protezione Idrogeologica [Padova] (IRPI), Institute of Geophysics [Austin] (IG), University of Texas at Austin [Austin], Istituto di Radioastronomia (IRA), Dipartimento di Ingegneria Elettrica e delle Tecnologie dell'Informazione [Napoli] (DIETI), Università degli studi di Napoli Federico II, Cornell University [New York], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], European Academy Bozen/Bolzano (EURAC), Stanford University, Royal Observatory of Belgium [Brussels] (ROB), Istituto di Radioastronomia [Bologna] (IRA), Lopes, R. M. C., Wall, S. D., Elachi, C., Birch, S. P. D., Corlies, P., Coustenis, A., Hayes, A. G., Hofgartner, J. D., Janssen, M. A., Kirk, R. L., Legall, A., Lorenz, R. D., Lunine, J. I., Malaska, M. J., Mastroguiseppe, M., Mitri, G., Neish, C. D., Notarnicola, C., Paganelli, F., Paillou, P., Poggiali, V., Radebaugh, J., Rodriguez, S., Schoenfeld, A., Soderblom, J. M., Solomonidou, A., Stofan, E. R., Stiles, B. W., Tosi, F., Turtle, E. P., West, R. D., Wood, C. A., Zebker, H. A., Barnes, J. W., Casarano, D., Encrenaz, P., Farr, T., Grima, C., Hemingway, D., Karatekin, O., Lucas, A., Mitchell, K. L., Ori, G., Orosei, R., Ries, P., Riccio, D., Soderblom, L. A., Zhang, Z., ITA, USA, FRA, and Hôpital Nord [CHU - APHM]-Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)
Subjects: Exploration of Saturn, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, Liquid methane, law.invention, Astrobiology, symbols.namesake, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, law, 0103 physical sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Radar, Enceladus, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, Cassini, radar, Titan, Planetary science, 13. Climate action, Space and Planetary Science, symbols, Titan (rocket family), Geology
Abstract: International audience; Titan was a mostly unknown world prior to the Cassini spacecraft’s arrival in July 2004. We review the major scientific advances made by Cassini’s Titan Radar Mapper (RADAR) during 13 years of Cassini’s exploration of Saturn and its moons. RADAR measurements revealed Titan’s surface geology, observed lakes and seas of mostly liquid methane in the polar regions, measured the depth of several lakes and seas, detected temporal changes on its surface, and provided key evidence that Titan contains an interior ocean. As a result of the Cassini mission, Titan has gone from an uncharted world to one that exhibits a variety of Earth-like geologic processes and surface-atmosphere interactions. Titan has also joined the ranks of “ocean worlds” along with Enceladus and Europa, which are prime targets for astrobiological research.
Published: 2019
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9. Titan’s 'Magic Islands': Transient features in a hydrocarbon sea

Author: Ralph D. Lorenz, Jason M. Soderblom, Claudia Notarnicola, Marco Mastrogiuseppe, Jonathan I. Lunine, Alexander G. Hayes, Jason D. Hofgartner, Michael Malaska, and Howard A. Zebker
Subjects: Sea level change, geological processes, 010504 meteorology & atmospheric sciences, radar observations, Titan, Ephemeral key, Astronomy and Astrophysics, 01 natural sciences, Seafloor spreading, Astrobiology, Radar observations, symbols.namesake, Space and Planetary Science, 0103 physical sciences, symbols, Titan (rocket family), 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract: The region of Titan’s hydrocarbon sea, Ligeia Mare, where transient bright features were previously discovered, was anomalously bright in the first of two more recent Cassini RADAR observations but not the second. Another transient bright feature in a different region of Ligeia Mare was also discovered in the first of the new observations. Here we present all the high-resolution observations of the regions containing these transient features and the quantitative constraints that we derived from them. We argue that these features are unlikely to be SAR image artifacts or permanent geophysical structures and thus their appearance is the result of ephemeral phenomena on Titan. We find that the transient features are more consistent with floating and/or suspended solids, bubbles, and waves than tides, sea level change, or seafloor change and based on the frequency of these phenomena in terrestrial settings, we consider waves to be the most probable hypothesis. These transient features are the first instance of active processes in Titan’s lakes and seas to be confirmed by multiple detections and demonstrate that Titan’s seas are not stagnant but rather dynamic environments.
Published: 2016
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10. Spatio-temporal Variation of Bright Ephemeral Features on Titan’s North Pole

Author: Rajani D. Dhingra, Jason W. Barnes, Christophe Sotin, Stéphane Le Mouélic, Robert H. Brown, Philip D. Nicholson, Jason M. Soderblom, Sebastien Rodriguez, Bonnie J. Buratti, Roger N. Clark, Kevin H. Baines, Michael Heslar, and Ralf Jaumann
Subjects: North pole, symbols.namesake, Geophysics, Space and Planetary Science, Ephemeral key, Earth and Planetary Sciences (miscellaneous), symbols, Astronomy and Astrophysics, Titan (rocket family), Atmospheric sciences, Geology
Abstract: We identify and document the instances of bright ephemeral features (BEF)—bright areas that appear, disappear, and shift from flyby to flyby on Titan’s north pole, using the Cassini Visual and Infrared Mapping Spectrometer data set, thereby developing a sense of their spatial distribution and temporal frequency. We find that BEFs have differing geographic location and spatial extents. However, they have similar observation geometries and orders of surface area coverage and are mostly accompanied by specular reflections. We find the BEFs to represent either broad specular reflection off of a recently wetted surface on the north pole of Titan or a near-surface fog—both owing to probable recent rainfalls. Our surface model constrains the surface roughness to be of 9°–15° indicating the approximate vertical relief of the region to be that of cobbles. We also find that within less than two Titan days the BEF (if on the surface) might infiltrate into the subsurface. We hypothesize the parts of BEFs that extend into the maria to be precipitation fog.
Published: 2020
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11. Stratification Dynamics of Titan’s Lakes via Methane Evaporation

Author: Vincent Chevrier, A. Engle, K. Farnsworth, Alejandro Soto, Stephen C. Tegler, Jordan K. Steckloff, Logan A. Pearce, Jason M. Soderblom, Jennifer Hanley, William M. Grundy, and Jessica J. Groven
Subjects: Molecular interactions, Ephemeral key, Stratification (water), chemistry.chemical_element, Astronomy and Astrophysics, Atmospheric sciences, Nitrogen, Methane, chemistry.chemical_compound, symbols.namesake, Geophysics, chemistry, Space and Planetary Science, Extraterrestrial life, Earth and Planetary Sciences (miscellaneous), symbols, Environmental science, Water cycle, Titan (rocket family)
Abstract: Saturn’s moon Titan is the only extraterrestrial body known to host stable lakes and a hydrological cycle. Titan’s lakes predominantly contain liquid methane, ethane, and nitrogen, with methane evaporation driving its hydrological cycle. Molecular interactions between these three species lead to nonideal behavior that causes Titan’s lakes to behave differently than Earth’s lakes. Here, we numerically investigate how methane evaporation and nonideal interactions affect the physical properties, structure, dynamics, and evolution of shallow lakes on Titan. We find that, under certain temperature regimes, methane-rich mixtures are denser than relatively ethane-rich mixtures. This allows methane evaporation to stratify Titan’s lakes into ethane-rich upper layers and methane-rich lower layers, separated by a strong compositional gradient. At temperatures above 86 K, lakes remain well mixed and unstratified. Between 84 and 86 K, lakes can stratify episodically. Below 84 K, lakes permanently stratify and develop very methane-depleted epilimnia. Despite small seasonal and diurnal deviations (
Published: 2020
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12. Spectral and emissivity analysis of the raised ramparts around Titan's northern lakes

Author: Olivier Witasse, R. J. Michaelides, S. D. Wall, A. Le Gall, Jason M. Soderblom, Pierre Drossart, Athena Coustenis, Charles Elachi, Kenneth J. Lawrence, Samuel Birch, Christos Matsoukas, A. Solomonidou, J. Yates, Maya Nasr, Jani Radebaugh, Alexander G. Hayes, R. M. C. Lopes, Michael Malaska, M. A. Janssen, Sebastien Rodriguez, Ashley Schoenfeld, European Space Astronomy Centre (ESAC), European Space Agency (ESA), California Institute of Technology (CALTECH), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Cornell University [New York], Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Physics Department [Stanford], Stanford University, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, Royal Institute of Technology [Stockholm] (KTH ), European Space Research and Technology Centre (ESTEC), Department of Geological Sciences [BYU], Brigham Young University (BYU), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), IMPEC - LATMOS, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), NASA-California Institute of Technology (CALTECH), Cornell University, Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Department of Physics [Stanford], and Stanford University [Stanford]
Subjects: Titan hydrology, 010504 meteorology & atmospheric sciences, Terrain, 01 natural sciences, law.invention, symbols.namesake, law, 0103 physical sciences, Radiative transfer, Emissivity, Radar, 010303 astronomy & astrophysics, Spectroscopy, 0105 earth and related environmental sciences, Remote sensing, Shore, geography, geography.geographical_feature_category, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Northern Hemisphere, Astronomy and Astrophysics, Radar observations, 13. Climate action, Space and Planetary Science, Titan surface, symbols, Radiometry, Titan (rocket family), Geology
Abstract: International audience; Some of Titan's small northern hemisphere lakes show raised rampart features (which are distinct from raised rims), and appear as SAR-bright mound-like annuli extending away from the lake for up to tens of kilometers from the shoreline. We investigate the infrared and microwave characteristics of these features using Cassini Visual and Infrared Mapping Spectrometer (VIMS) and RADAR data. A spectral comparative analysis is performed among the lakes, their ramparts, and the surrounding regions. We overcome the profound difference in spatial resolution between VIMS and SAR data by using a method that provides overlays between the spectral images and SAR, thus enabling the correct selection of VIMS pixels. The surface properties of the selected areas are obtained using a radiative transfer analysis on the selected VIMS pixels, in addition to emissivity obtained from the RADAR in radiometry mode. Analysis of these combined and co-registered data provides constraints for the formation mechanism(s) of raised ramparts. The results show that the emissivity of the raised ramparts is close to that of Titan's labyrinthic terrains and to that of empty lake floors in the northern polar regions. This is confirmed by the VIMS analysis that also shows that the infrared spectral response of the raised ramparts is very similar to that of some empty lake floors. This suggests that both areas are made from or are covered by a similar material. In addition, two out of the eight lakes with raised ramparts show spectral differences at three specific wavelengths, 1.6, 2.0, and 5.0 μm, between the ramparts and the surrounding terrain. We hypothesize that this could be due to some component, or mixture of components in the ramparts that is less absorbent at these specific wavelengths, or it could be an effect of different grain sizes. These observations provide first insights into the possible mechanisms leading to the formation of the raised ramparts that are discussed here.
Published: 2020
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13. Observational Evidence for Summer Rainfall at Titan's North Pole

Author: Jason W. Barnes, P. D. Nicholson, Sebastien Rodriguez, Bonnie J. Burrati, Ralf Jauman, Elizabeth P. Turtle, Christophe Sotin, Kevin H. Baines, Don E. Jennings, Jason Perry, Roger N. Clark, Rajani D. Dhingra, Jason M. Soderblom, V. Cottini, Stéphane Le Mouélic, Robert H. Brown, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Cornell University [New York], MIT, Earth Atmospher & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), and NASA Goddard Space Flight Center (GSFC)
Subjects: North pole, ComputerSystemsOrganization_COMPUTERSYSTEMIMPLEMENTATION, 010504 meteorology & atmospheric sciences, GeneralLiterature_INTRODUCTORYANDSURVEY, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], ComputerApplications_COMPUTERSINOTHERSYSTEMS, 010502 geochemistry & geophysics, 01 natural sciences, Observational evidence, symbols.namesake, Geophysics, Climatology, symbols, General Earth and Planetary Sciences, Titan (rocket family), Geology, 0105 earth and related environmental sciences
Abstract: International audience; Methane rain on Saturn's moon Titan makes it the only place, other than Earth, where rain interacts with the surface. When and where that rain wets the surface changes seasonally in ways that remain poorly understood. Here we report the discovery of a bright ephemeral feature covering an area of 120,000 km 2 near Titan's north pole in observations from Cassini's near-infrared instrument, Visual and Infrared Mapping Spectrometer on 7 June 2016. Based on the overall brightness, spectral characteristics, and geologic context, we attribute this new feature to specular reflections from a rain-wetted solid surface like those off of a sunlit wet sidewalk. The reported observation is the first documented rainfall event at Titan's north pole and heralds the arrival of the northern summer (through climatic evidence), which has been delayed relative to model predictions. This detection helps constrain Titan's seasonal change and shows that the "wet-sidewalk effect can be used to identify other rain events." Plain Language Summary Cassini arrived in the Saturnian system in the southern summers of 2004. As expected, the Cassini team observed cloud cover, storms, and precipitation on the south pole. Like Earth, Titan has an axial tilt (27 •) and its seasons vary over its year (30 Earth years). Ever since this shift in season began, the Cassini team eagerly waited for observations indicating cloud cover and precipitation that went missing from the northern latitudes. Our rainfall observation at the north pole is a major finding for two important reasons. First, this discovery observation heralds the much awaited arrival of the north polar summer rainstorms on Titan. This atmospheric phenomenon has been delayed compared to the theoretical predictions and was perplexing Titan researchers and climate modelers especially because the north pole hosts most of Titan's lakes and seas. Second, it is extremely difficult to detect rainfall events on Titan due to its thick atmospheric haze and very limited opportunities to view the surface (and its changes). We have used a novel phenomenon-the smoothening of a previously dry, rough surface by a thin layer of fluid after rainfall, similar to a wet sidewalk-as evidence for rainfall events on the surface of Titan.
Published: 2019
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14. Observational evidence for active dust storms on Titan at equinox

Author: Clément Narteau, Roger N. Clark, Benjamin Charnay, T. Appéré, S. Courrech du Pont, Jason M. Soderblom, Thomas Cornet, B. J. Buratti, J. Bow, G. Vixie, Jasper F. Kok, Jason W. Barnes, Ralf Jaumann, Philip D. Nicholson, Mathieu Hirtzig, Pascal Rannou, S. Le Mouélic, Olivier Bourgeois, Jani Radebaugh, L. Maltagliati, Ralph D. Lorenz, Kevin H. Baines, Sebastien Rodriguez, Robert H. Brown, Christophe Sotin, Antoine Lucas, S. Rafkin, Caitlin A. Griffith, Katrin Stephan, Athena Coustenis, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), College of Earth, Ocean and Atmospheric Sciences [Corvallis] (CEOAS), Oregon State University (OSU), Christ University, Bangalore, India, Department of Space Studies [Boulder], Southwest Research Institute [Boulder] (SwRI), University of Arizona, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Department of Geological Sciences [BYU], Brigham Young University (BYU), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Groupe de spectrométrie moléculaire et atmosphérique (GSMA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), Department of Planetary Sciences [Tucson], University of Idaho [Moscow, USA], Matière et Systèmes Complexes (MSC (UMR_7057)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), DLR Institute of Planetary Research, German Aerospace Center (DLR), Faculty of Sciences [Lebanese University], Lebanese University [Beirut] (LU), John Innes Centre [Norwich], Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH)-NASA, Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Southwest Research Institute [San Antonio] (SwRI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Centre de Formation et de Recherche sur les Environnements Méditérranéens (CEFREM), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Centre de physique moléculaire optique et hertzienne (CPMOH), Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Lebanese University [Beirut], Laboratoire d'Electronique et des Technologies de l'Information (CEA-LETI), Université Grenoble Alpes (UGA)-Direction de Recherche Technologique (CEA) (DRT (CEA)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université de Perpignan Via Domitia (UPVD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Centre National de la Recherche Scientifique (CNRS), and Matière et Systèmes Complexes (MSC)
Subjects: Haze, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Equator, Equinox, 01 natural sciences, Methane, Astrobiology, chemistry.chemical_compound, symbols.namesake, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, dust storm, 0103 physical sciences, Radiative transfer, Meteorology & Atmospheric Sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [MATH]Mathematics [math], [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], Storm, Planetengeologie, chemistry, 13. Climate action, [SDU]Sciences of the Universe [physics], symbols, General Earth and Planetary Sciences, Aeolian processes, Cassini, Titan, Titan (rocket family)
Abstract: Saturn’s moon Titan has a dense nitrogen-rich atmosphere, with methane as its primary volatile. Titan’s atmosphere experiences an active chemistry that produces a haze of organic aerosols that settle to the surface and a dynamic climate in which hydrocarbons are cycled between clouds, rain and seas. Titan displays particularly energetic meteorology at equinox in equatorial regions, including sporadic and large methane storms. In 2009 and 2010, near Titan’s northern spring equinox, the Cassini spacecraft observed three distinctive and short-lived spectral brightenings close to the equator. Here, we show from analyses of Cassini spectral data, radiative transfer modelling and atmospheric simulations that the brightenings originate in the atmosphere and are consistent with formation from dust storms composed of micrometre-sized solid organic particles mobilized from underlying dune fields. Although the Huygens lander found evidence that dust can be kicked up locally from Titan’s surface, our findings suggest that dust can be suspended in Titan’s atmosphere at much larger spatial scale. Mobilization of dust and injection into the atmosphere would require dry conditions and unusually strong near-surface winds (about five times more than estimated ambient winds). Such strong winds are expected to occur in downbursts during rare equinoctial methane storms—consistent with the timing of the observed brightenings. Our findings imply that Titan—like Earth and Mars—has an active dust cycle, which suggests that Titan’s dune fields are actively evolving by aeolian processes. Saturn’s moon Titan may have an active dust cycle in equatorial regions driven by storm winds, Cassini observations consistent with dust suspension in Titan’s atmosphere suggest.
Published: 2018
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15. Spherical Radiative Transfer in C++ (SRTC++): A Parallel Monte Carlo Radiative Transfer Model for Titan

Author: Brian Jackson, Sebastien Rodriguez, Jason W. Barnes, Christophe Sotin, Jason M. Soderblom, Thomas Cornet, Shannon MacKenzie, Máté Ádámkovics, Eliot F. Young, Laura Trouille, University of Idaho [Moscow, USA], Department of Physics [Moscow,USA], Southwest Research Institute [Boulder] (SwRI), Adler Planetarium, Chicago, IL 60605 USA, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Boise State Univ, Dept Phys, Boise, ID 83725 USA, Clemson Univ, Phys & Astron Dept, Clemson, SC 29634 USA, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), and MIT, Earth Atmospher & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA
Subjects: Physics, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Monte Carlo method, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy and Astrophysics, 01 natural sciences, Computational physics, symbols.namesake, Atmospheric radiative transfer codes, Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, symbols, Radiative transfer, Titan (rocket family), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, ComputingMethodologies_COMPUTERGRAPHICS
Abstract: International audience; We present a new computer program, SRTC++, to solve spatial problems associated with explorations of Saturn's moon Titan. The program implements a three-dimensional structure well-suited to addressing shortcomings arising from plane-parallel radiative transfer approaches. SRTC++ʼs design uses parallel processing in an object-oriented, compiled computer language (C++) leading to a flexible and fast architecture. We validate SRTC++ using analytical results, semianalytical radiative transfer expressions, and an existing Titan plane-parallel model. SRTC+ + complements existing approaches, addressing spatial problems like near-limb and near-terminator geometries, non-Lambertian surface phase functions (including specular reflections), and surface albedo nonuniformity.
Published: 2018
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16. A radar map of Titan Seas: Tidal dissipation and ocean mixing through the throat of Kraken

Author: Alexander G. Hayes, Özgür Karatekin, Ralph D. Lorenz, Randolph L. Kirk, Tetsuya Tokano, Y. Anderson, Jason M. Soderblom, Michael Malaska, Jonathan I. Lunine, Antoine Lucas, Stephen D. Wall, and Elizabeth P. Turtle
Subjects: Shore, geography, geography.geographical_feature_category, Evaporite, Kraken, Astronomy and Astrophysics, Geophysics, law.invention, Ocean surface topography, symbols.namesake, Depth sounding, Oceanography, Space and Planetary Science, law, symbols, Bathymetry, Radar, Titan (rocket family), Geology
Abstract: We present a radar map of the Titan’s seas, with bathymetry estimated as proportional to distance from the nearest shore. This naive analytic bathymetry, scaled to a recent radar sounding of Ligeia Mare, suggests a total liquid volume of ∼32,000 km 3 , at the low end of estimates made in 2008 when mapping coverage was incomplete. We note that Kraken Mare has two principal basins, separated by a narrow (∼17 km wide, ∼40 km long) strait we refer to as the ‘throat’. Tidal currents in this strait may be dramatic (∼0.5 m/s), generating observable effects such as dynamic topography, whirlpools, and acoustic noise, much like tidal races on Earth such as the Corryvreckan off Scotland. If tidal flow through this strait is the dominant mixing process, the two basins take ∼20 Earth years to exchange their liquid inventory. Thus compositional differences over seasonal timescales may exist, but the composition of solutes (and thus evaporites) over Croll–Milankovich timescales should be homogenized.
Published: 2014
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17. Explorer of Enceladus and Titan (E2T): Investigating ocean worlds' evolution and habitability in the solar system

Author: Jason W. Barnes, Nathalie Carrasco, Roberto Orosei, Athena Coustenis, Andre Wong, Jean Pierre Paul de Vera, Paolo Tortora, Francesca Ferri, Andrea Martelli, Giuseppe Mitri, Andrea D'Ottavio, Marco Zannoni, Anastassios E. Petropoulos, Frank Postberg, Ralph D. Lorenz, Audrey Vorburger, Jason M. Soderblom, Kim Reh, J. Schmidt, Véronique Vuitton, Ralf Srama, Alexander Hayes, Marco Berga, Bernd Abel, Gabriel Tobie, Paul O. Hayne, Christophe Sotin, Peter Wurz, Sascha Kempf, Jon K. Hillier, Jean-Pierre Lebreton, Mitri, Giuseppe, Postberg, Frank, Soderblom, Jason M., Wurz, Peter, Tortora, Paolo, Abel, Bernd, Barnes, Jason W., Berga, Marco, Carrasco, Nathalie, Coustenis, Athena, Paul de Vera, Jean Pierre, D'Ottavio, Andrea, Ferri, Francesca, Hayes, Alexander G., Hayne, Paul O., Hillier, Jon K., Kempf, Sascha, Lebreton, Jean-Pierre, Lorenz, Ralph D., Martelli, Andrea, Orosei, Roberto, Petropoulos, Anastassios E., Reh, Kim, Schmidt, Juergen, Sotin, Christophe, Srama, Ralf, Tobie, Gabriel, Vorburger, Audrey, Vuitton, Véronique, Wong, Andre, Zannoni, Marco, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Klaus-Tachira-Laboratory for Cosmochemistry, Heidelberg University, Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Physikalisches Institut [Bern], Universität Bern [Bern], Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), Universität Leipzig [Leipzig], University of Idaho [Moscow, USA], Thales Alenia Space Italia, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Deutsches Zentrum für Luft- und Raumfahrt (DLR), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Universita degli Studi di Padova, Center for Radiophysics and Space Research [Ithaca] (CRSR), Cornell University [New York], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), University of Kent [Canterbury], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Istituto di Radioastronomia [Bologna] (IRA), Istituto Nazionale di Astrofisica (INAF), University of Oulu, Institut für Raumfahrtsysteme (IRS), Universität Stuttgart [Stuttgart], University of Bern, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ITA, USA, GBR, FRA, DEU, FIN, CHE, Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Università di Bologna [Bologna] (UNIBO), IMPEC - LATMOS, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Cornell University, California Institute of Technology (CALTECH)-NASA, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Istituto di Radioastronomia (IRA), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Solar System, Cosmic Vision, 010504 meteorology & atmospheric sciences, Habitability, Terrain, 01 natural sciences, Astrobiology, Atmosphere, Origin of volatiles, symbols.namesake, Enceladus, Saturn, 0103 physical sciences, 010303 astronomy & astrophysics, Origin of volatile, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, Astronomy and Astrophysic, 13. Climate action, Space and Planetary Science, symbols, Enceladu, Titan (rocket family), Titan, Geology
Abstract: International audience; Titan, with its organically rich and dynamic atmosphere and geology, and Enceladus, with its active plume, both harbouring global subsurface oceans, are prime environments in which to investigate the habitability of ocean worlds and the conditions for the emergence of life. We present a space mission concept, the Explorer of Enceladus and Titan (E2T), which is dedicated to investigating the evolution and habitability of these Saturnian satellites. E2T is proposed as a medium-class mission led by ESA in collaboration with NASA in response to ESA's M5 Cosmic Vision Call. E2T proposes a focused payload that would provide in-situ composition investigations and high-resolution imaging during multiple flybys of Enceladus and Titan using a solar-electric powered spacecraft in orbit around Saturn. The E2T mission would provide high-resolution mass spectrometry of the plume currently emanating from Enceladus' south polar terrain and of Titan's changing upper atmosphere. In addition, high-resolution infrared (IR) imaging would detail Titan's geomorphology at 50–100 m resolution and the temperature of the fractures on Enceladus' south polar terrain at meter resolution. These combined measurements of both Titan and Enceladus would enable the E2T mission scenario to achieve two major scientific goals: 1) Study the origin and evolution of volatile-rich ocean worlds; and 2) Explore the habitability and potential for life in ocean worlds. E2T's two high-resolution time-of-flight mass spectrometers would enable resolution of the ambiguities in chemical analysis left by the NASA/ESA/ASI Cassini-Huygens mission regarding the identification of low-mass organic species, detect high-mass organic species for the first time, further constrain trace species such as the noble gases, and clarify the evolution of solid and volatile species. The high-resolution IR camera would reveal the geology of Titan's surface and the energy dissipated by Enceladus' fractured south polar terrain and plume in detail unattainable by the Cassini mission.
Published: 2017
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18. Geomorphological map of the Afekan Crater region, Titan: Terrain relationships in the equatorial and mid-latitude regions

Author: Ralph D. Lorenz, Ashley Schoenfeld, Michael Janssen, Rosaly M. C. Lopes, Alexander G. Hayes, David A. Williams, Jani Radebaugh, Elizabeth P. Turtle, Catherine D. Neish, Jason M. Soderblom, Samuel Birch, Tom G. Farr, Alice Le Gall, Michael Malaska, A. Solomonidou, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), ASU School of Earth and Space Exploration (SESE), Arizona State University [Tempe] (ASU), Department of Physics and Space Sciences [FIT], Florida Institute of Technology [Melbourne], Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Department of Astronomy [Ithaca], Cornell University [New York], PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ESTER - LATMOS, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Department of Geological Sciences [BYU], and Brigham Young University (BYU)
Subjects: Synthetic aperture radar, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Terrain, 01 natural sciences, law.invention, symbols.namesake, Impact crater, law, 0103 physical sciences, Sequence stratigraphy, Radar, 010303 astronomy & astrophysics, Geomorphology, 0105 earth and related environmental sciences, Remote sensing, Astronomy and Astrophysics, 15. Life on land, 13. Climate action, Space and Planetary Science, Middle latitudes, Titan surface, symbols, Aeolian processes, Geological processes, Titan (rocket family), Titan, Geology
Abstract: International audience; We carried out geomorphological mapping in a mid-latitude area surrounding the Afekan Crater region on Titan. We used Cassini RADAR (Synthetic Aperture Radar mode) data as the basemap, supplemented by Cassini RADAR microwave emissivity, Imaging Science Subsystem (ISS) infrared data, Visual and Infrared Mapping Spectrometer (VIMS) spectral images, and topography derived from Synthetic Aperture Radar (SAR). Mapping was done at a spatial scale of 300 m/pixel, which corresponds to a map scale of 1:800,000. We describe multiple terrain units and their spatial relations. We describe five broad classes of units that are in agreement with previous mapping efforts: crater, labyrinth, hummocky/mountainous, plains, and dune terrain classes. We subdivide these into seven crater units, four hummocky/mountainous units, six plains units, and three dunes units. Our results show that plains are the dominant unit in Titan’s mid latitudes. Of the plains units, the undifferentiated plains are the largest by total areal extent in the mapped region, accounting for over 45% of the mapped area. We developed a stratigraphic sequence that has the hummocky/mountainous and labyrinth terrains as the oldest units. The observed properties of the hummocky/mountainous terrain are consistent with fractured water ice materials, while the labyrinth terrains are consistent with organic materials. The youngest units are the dune units and streak-like plains units, with the undifferentiated plains units being of intermediate age. The microwave emissivity of the undifferentiated plains and dune units are consistent with organic materials. Given their properties and stratigraphic placement, we conclude that the hummocky/mountainous terrains are most consistent with the presumed crustal materials of Titan. The plains materials are consistent with deposits resulting from the transport and emplacement of organic-rich materials predominantly by aeolian mechanisms. Our geomorphological mapping results are consistent with the equatorial and mid-latitudes of Titan being dominated by organic materials that have been deposited and emplaced by aeolian activity.
Published: 2016
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19. A newly discovered impact crater in Titan's Senkyo: Cassini VIMS observations and comparison with other impact features

Author: Philip D. Nicholson, Jason W. Barnes, Roger N. Clark, Christophe Sotin, Robert H. Brown, S. Le Mouélic, Jason M. Soderblom, K. J. Lawrence, Kevin H. Baines, and Bonnie J. Buratti
Subjects: symbols.namesake, Impact crater, Space and Planetary Science, symbols, Ejecta blanket, Fluvial, Astronomy and Astrophysics, Mass wasting, Titan (rocket family), Geomorphology, Geology, Astrobiology, Plume
Abstract: Senkyo is an equatorial plain on Titan filled with dunes and surrounded by hummocky plateaus. During the Titan targeted flyby T61 on August 25, 2009, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed a circular feature, centered at 5.4° N and 341°W, that superimposes the dune fields and a bright plateau. This circular feature, which has been named Paxsi by the International Astronomical Union, is 120±10 km in diameter (measured from the outer edge of the crater rim) and exhibits a central bright area that can be interpreted as the central peak or pit of an impact crater. Although there are only a handful of certain impact craters on Titan, there are two other craters that are of similar size to this newly discovered feature and that have been studied by VIMS: Sinlap ( Le Mouelic et al., 2008 ) and Selk ( Soderblom et al., 2010 ). Sinlap is associated with a large downwind, fan-like feature that may have been formed from an impact plume that rapidly expanded and deposited icy particles onto the surface. Although much of the surrounding region is covered with dunes, the plume region is devoid of dunes. The formation process of Selk also appears to have removed (or covered up) dunes from parts of the adjacent dune-filled terrain. The circular feature on Senkyo is quite different: there is no evidence of an ejecta blanket and the crater itself appears to be infilled with dune material. The rim of the crater appears to be eroded by fluvial processes; at one point the rim is breached. The rim is unusually narrow, which may be due to mass wasting on its inside and subsequent infill by dunes. Based on these observations, we interpret this newly discovered feature to be a more eroded crater than both Sinlap and Selk. Paxsi may have formed during a period when Titan was warmer and more ductile than it is currently.
Published: 2012
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20. Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan’s surface properties

Author: Alberto Adriani, T. B. McCord, Robert H. Brown, Jason W. Barnes, Angioletta Coradini, Dale P. Cruikshank, Philip D. Nicholson, Federico Tosi, Roberto Seu, M. A. Janssen, Roberto Orosei, Jason M. Soderblom, A. I. Gavrishin, Jonathan I. Lunine, Fabrizio Capaccioni, Enrico Flamini, A. Negrão, Roger N. Clark, Richard D. West, Lauren Wye, Gianrico Filacchione, S. D. Wall, Maria Luisa Moriconi, and Priscilla Cerroni
Subjects: titan, infrared observations, spectroscopy, Brightness, Backscatter, Pixel, Hyperspectral imaging, radar observations, Astronomy and Astrophysics, Scatterometer, law.invention, symbols.namesake, Space and Planetary Science, law, symbols, Radar, Titan (rocket family), Image resolution, Geology, Remote sensing
Abstract: We apply a multivariate statistical method to Titan data acquired by different instruments onboard the Cassini spacecraft. We have searched through Cassini/VIMS hyperspectral cubes, selecting those data with convenient viewing geometry and that overlap with Cassini/RADAR scatterometry footprints with a comparable spatial resolution. We look for correlations between the infrared and microwave ranges the two instruments cover. Where found, the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for incidence angle, and the calibrated antenna temperature measured along with the scatterometry echoes, are combined with the infrared reflectances, with estimated errors, to produce an aggregate data set, that we process using a multivariate classification method to identify homogeneous taxonomic units in the multivariate space of the samples. In medium resolution data (from 20 to 100 km/pixel), sampling relatively large portions of the satellite’s surface, we find regional geophysical units matching both the major dark and bright features seen in the optical mosaic. Given the VIMS cubes and RADAR scatterometer passes considered in this work, the largest homogeneous type is associated with the dark equatorial basins, showing similar characteristics as each other on the basis of all the considered parameters. On the other hand, the major bright features seen in these data generally do not show the same characteristics as each other. Xanadu, the largest continental feature, is as bright as the other equatorial bright features, while showing the highest backscattering coefficient of the entire satellite. Tsegihi is very bright at 5 μm but it shows a low backscattering coefficient, so it could have a low roughness on a regional scale and/or a different composition. Another well-defined region, located southwest of Xanadu beyond the Tui Regio, seems to be detached from the surrounding terrains, being bright at 2.69, 2.78 and 5 μm but having a low radar brightness. In this way, other units can be found that show correlations or anti-correlations between the scatterometric response and the spectrophotometric behavior, not evident from the optical remote sensing data.
Published: 2010
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21. DIELECTRIC PROPERTIES OF CRYOGENIC LIQUID ALKANES, AND THE FATE OF PROPANE IN SEAS ON TITAN

Author: Karl L. Mitchell, Michael J. Malaska, Ralph D. Lorenz, Mathieu Choukroun, Alice Le Gall, M. Mastrogiuseppe, C. S. Jamieson, Jonathan Lunine, Jason M. Soderblom, Martin B. Barmatz, and Alexander Hayes
Subjects: chemistry.chemical_compound, symbols.namesake, Materials science, chemistry, Chemical engineering, Propane, symbols, Organic chemistry, Dielectric, Titan (rocket family)
Published: 2016
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22. Spectral properties of Titan's impact craters imply chemical weathering of its surface

Author: Jason W. Barnes, S. Le Mouélic, Philip D. Nicholson, Robert H. Brown, Michael Malaska, Jason M. Soderblom, R. L. Kirk, Bryan Stiles, B. J. Buratti, Kevin H. Baines, Catherine D. Neish, Christophe Sotin, Roger N. Clark, Shannon MacKenzie, A. Le Gall, Department of Physics and Space Sciences [FIT], Florida Institute of Technology [Melbourne], Department of Physics [Moscow,USA], University of Idaho [Moscow, USA], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Massachusetts Institute of Technology (MIT), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrogeology Science Center [Flagstaff], United States Geological Survey [Reston] (USGS), ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, US Geological Survey [Denver], Department of Astronomy [Ithaca], and Cornell University [New York]
Subjects: [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, Fluvial, Weathering, Erosion and weathering, Methane, Astrobiology, symbols.namesake, chemistry.chemical_compound, Planetary Sciences: Solar System Objects, Impact crater, Impact Phenomena, Cratering, Research Letter, Ejecta, Planetary Sciences: Solid Surface Planets, Spectral properties, Impact Phenomena, Research Letters, Tectonophysics, Geophysics, chemistry, 13. Climate action, symbols, General Earth and Planetary Sciences, Impact cratering, Planetary Sciences: Comets and Small Bodies, Water ice, Titan (rocket family), Titan, Geology
Abstract: We examined the spectral properties of a selection of Titan's impact craters that represent a range of degradation states. The most degraded craters have rims and ejecta blankets with spectral characteristics that suggest that they are more enriched in water ice than the rims and ejecta blankets of the freshest craters on Titan. The progression is consistent with the chemical weathering of Titan's surface. We propose an evolutionary sequence such that Titan's craters expose an intimate mixture of water ice and organic materials, and chemical weathering by methane rainfall removes the soluble organic materials, leaving the insoluble organics and water ice behind. These observations support the idea that fluvial processes are active in Titan's equatorial regions., Key Points We examine the spectral properties of Titan's impact cratersDegraded crater rims are more enriched in water ice than fresh crater rimsObservations suggest chemical weathering of organics in water ice matrix
Published: 2015
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23. Evidence of Titan’s climate history from evaporite distribution

Author: Bonnie J. Buratti, T. B. McCord, Jason W. Barnes, Sebastien Rodriguez, Stéphane Le Mouélic, Christophe Sotin, Shannon MacKenzie, Jason M. Soderblom, R. N. Clark, P. D. Nicholson, Kevin H. Baines, Department of Physics [Moscow,USA], University of Idaho [Moscow, USA], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Space Science and Engineering Center [Madison] (SSEC), University of Wisconsin-Madison, US Geological Survey [Denver], United States Geological Survey [Reston] (USGS), Department of Astronomy [Ithaca], Cornell University [New York], This work was supported by NASA Cassini Data Analysts and Participating Scientists (CDAPS) Grant #NNX12AC28G to JWB. C.S. acknowledges support from the NASA Astrobiology Institute. Part of this work was conducted at JPL/Caltech under contract with NASA., University of Arizona, Planetary Science Institute [Tucson] (PSI), and Bear Fight Institute
Subjects: Earth and Planetary Astrophysics (astro-ph.EP), Evaporite, Infrared observations, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astronomy and Astrophysics, Climate history, Astrobiology, symbols.namesake, Paleontology, Space and Planetary Science, Global distribution, [SDU]Sciences of the Universe [physics], Titan surface, symbols, Polar, Geological processes, Titan (rocket family), Titan, Geology, Spectroscopy, Astrophysics - Earth and Planetary Astrophysics
Abstract: International audience; Water-ice-poor, 5-lm-bright material on Saturn's moon Titan has previously been geomorphologically identified as evaporitic. Here we present a global distribution of the occurrences of the 5-lm-bright spectral unit, identified with Cassini's Visual Infrared Mapping Spectrometer (VIMS) and examined with RADAR when possible. We explore the possibility that each of these occurrences are evaporite deposits. The 5-lm-bright material covers 1% of Titan's surface and is not limited to the poles (the only regions with extensive, long-lived surface liquid). We find the greatest areal concentration to be in the equatorial basins Tui Regio and Hotei Regio. Our interpretations, based on the correlation between 5-lm-bright material and lakebeds, imply that there was enough liquid present at some time to create the observed 5-lm-bright material. We address the climate implications surrounding a lack of evaporitic material at the south polar basins: if the south pole basins were filled at some point in the past, then where is the evaporite?
Published: 2014
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24. Cassini/VIMS observes rough surfaces on Titan’s Punga Mare in specular reflection

Author: Mark A. Donelan, Stéphane Le Mouélic, Jason M. Soderblom, Kevin H. Baines, Robert H. Brown, Sebastien Rodriguez, Alexander G. Hayes, Thomas B. McCord, Jason W. Barnes, Christophe Sotin, University of Idaho [Moscow, USA], Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Arizona, Lunar and Planetary Laboratory [Tucson] (LPL), Department of Astronomy [Ithaca], Cornell University [New York], Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami [Coral Gables], Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and University of Wisconsin-Madison
Subjects: North pole, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Surface finish, Geophysics, Geographic distribution, symbols.namesake, Planetary science, Geography, [SDU]Sciences of the Universe [physics], symbols, 14. Life underwater, Specular reflection, Hydrology, Titan (rocket family), Titan, ComputingMilieux_MISCELLANEOUS, Remote sensing, Original Research
Abstract: Cassini/VIMS high-phase specular observations of Titan’s north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $2^{+2}_{-1}$ \end{document}2−1+2 cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan’s seas, and also the first extraterrestrial sea-surface waves in general.
Published: 2014
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25. Science goals and mission concept for the future exploration of Titan and Enceladus

Author: Jason M. Soderblom, François Raulin, Frank Postberg, Katrin Stephan, Joseph Westlake, Anezina Solomonidou, Robert A. West, Francis Nimmo, Nathalie Carrasco, E.R. Stofan, Elizabeth P. Turtle, Dirk Schulze-Makuch, Roland Wagner, Giuseppe Mitri, A. Lefèvre, Daniel Cordier, Gabriel Tobie, Athena Coustenis, Ralf Jaumann, Timothy A. Livengood, Andrew J. Coates, L. Norman, Jean-Pierre Lebreton, Robert T. Pappalardo, Wolf D. Geppert, R. de Kok, Juergen Schmidt, Sebastien Rodriguez, Conor A. Nixon, Kathleen Mandt, Nicholas A Teanby, Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), School of Earth Sciences [Bristol], University of Bristol [Bristol], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), DLR Institute of Planetary Research, German Aerospace Center (DLR), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS), University of Potsdam, IMPEC - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), SRON Netherlands Institute for Space Research (SRON), Stockholm University, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Space Science and Engineering Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Department of Earth and Planetary Sciences [Santa Cruz], University of California [Santa Cruz] (UCSC), University of California-University of California, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Universität Heidelberg [Heidelberg], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Washington State University (WSU), Massachusetts Institute of Technology (MIT), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), University of Potsdam = Universität Potsdam, PLANETO - LATMOS, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Department of Physics [Stockholm], European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), University of California [Santa Cruz] (UC Santa Cruz), University of California (UC)-University of California (UC), NASA-California Institute of Technology (CALTECH), Institut für Geowissenschaften [Heidelberg], Universität Heidelberg [Heidelberg] = Heidelberg University, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Faculty of Geology and Geoenvironment [Athens], National and Kapodistrian University of Athens (NKUA), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire de Planétologie et Géodynamique de Nantes ( LPGN ), Université de Nantes ( UN ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), German Aerospace Center ( DLR ), Laboratoire inter-universitaire des systèmes atmosphèriques ( LISA ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université Paris Diderot - Paris 7 ( UPD7 ) -Université Paris-Est Créteil Val-de-Marne - Paris 12 ( UPEC UP12 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Mullard Space Science Laboratory ( MSSL ), University College of London [London] ( UCL ), Laboratoire d'astrophysique de l'observatoire de Besançon ( LAOB ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Franche-Comté ( UFC ), SRON Netherlands Institute for Space Research ( SRON ), Institut de Planétologie et d'Astrophysique de Grenoble ( IPAG ), Observatoire des Sciences de l'Univers de Grenoble ( OSUG ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), NASA Goddard Space Flight Center ( GSFC ), Southwest Research Institute [San Antonio] ( SwRI ), University of California [Santa Cruz] ( UCSC ), Jet Propulsion Laboratory ( JPL ), NASA-California Institute of Technology ( CALTECH ), Astrophysique Interactions Multi-échelles ( AIM - UMR 7158 - UMR E 9005 ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Paris Diderot - Paris 7 ( UPD7 ), Washington State University ( WSU ), Massachusetts Institute of Technology ( MIT ), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] ( APL ), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université de Franche-Comté (UFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Exploration of Saturn, Ocean, Solar System, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 7. Clean energy, Missions, Space exploration, Astrobiology, symbols.namesake, Enceladus, Interior, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmosphere, Institut für Physik und Astronomie, Astronomy, Astronomy and Astrophysics, Planetengeologie, Surface, [ PHYS.PHYS.PHYS-AO-PH ] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], 13. Climate action, Space and Planetary Science, symbols, Titan (rocket family), Titan, Geology
Abstract: International audience; Saturn's moons, Titan and Enceladus, are two of the Solar System's most enigmatic bodies and are prime targets for future space exploration. Titan provides an analogue for many processes relevant to the Earth, more generally to outer Solar System bodies, and a growing host of newly discovered icy exoplanets. Processes represented include: atmospheric dynamics, complex organic chemistry, meteorological cycles (with methane as a working fluid), astrobiology, surface liquids and lakes, geology, fluvial and aeolian erosion, and interactions with an external plasma environment. In addition, exploring Enceladus over multiple targeted flybys will give us a unique opportunity to further study the most active icy moon in our Solar System as revealed by Cassini and to analyse in situ its active plume with highly capable instrumentation addressing its complex chemistry and dynamics. Enceladus' plume likely represents the most accessible samples from an extra-terrestrial liquid water environment in the Solar system, which has far reaching implications for many areas of planetary and biological science. Titan with its massive atmosphere and Enceladus with its active plume are prime planetary objects in the Outer Solar System to perform in situ investigations. In the present paper, we describe the science goals and key measurements to be performed by a future exploration mission involving a Saturn-Titan orbiter and a Titan balloon, which was proposed to ESA in response to the call for definition of the science themes of the next Large-class mission in 2013. The mission scenario is built around three complementary science goals: (A) Titan as an Earth-like system; (B) Enceladus as an active cryovolcanic moon; and (C) Chemistry of Titan and Enceladus – clues for the origin of life. The proposed measurements would provide a step change in our understanding of planetary processes and evolution, with many orders of magnitude improvement in temporal, spatial, and chemical resolution over that which is possible with Cassini-Huygens. This mission concept builds upon the successes of Cassini-Huygens and takes advantage of previous mission heritage in both remote sensing and in-situ measurement technologies.
Published: 2014
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26. Precipitation-induced surface brightenings seen on Titan by Cassini VIMS and ISS

Author: Paul O. Hayne, Stéphane Le Mouélic, Laurence A. Soderblom, Robert H. Brown, Bonnie J. Buratti, Philip D. Nicholson, Thomas B. McCord, Jason M. Soderblom, J. Bow, Jason Perry, Michael Malaska, Roger N. Clark, Christophe Sotin, Jason W. Barnes, Paul A. Dalba, Ralph D. Lorenz, Kevin H. Baines, Elizabeth P. Turtle, Ralf Jaumann, Sebastien Rodriguez, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Soderblom, Jason, University of Idaho [Moscow, USA], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, New York Presbyterian Hospital, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Planetary Science Institute [Tucson] (PSI), Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Department of Astronomy [Ithaca], and Cornell University [New York]
Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Atmosphere, Atmospheric sciences, Latitude, symbols.namesake, Geography, Planetary science, symbols, General pattern, Surface layer, Hydrology, Cloudburst, Titan, Titan (rocket family)
Abstract: Observations from Cassini VIMS and ISS show localized but extensive surface brightenings in the wake of the 2010 September cloudburst. Four separate areas, all at similar latitude, show similar changes: Yalaing Terra, Hetpet Regio, Concordia Regio, and Adiri. Our analysis shows a general pattern to the time-sequence of surface changes: after the cloudburst the areas darken for months, then brighten for a year before reverting to their original spectrum. From the rapid reversion timescale we infer that the process driving the brightening owes to a fine-grained solidified surface layer. The specific chemical composition of such solid layer remains unknown. Evaporative cooling of wetted terrain may play a role in the generation of the layer, or it may result from a physical grain-sorting process., National Aeronautics and Space Administration. ESA Cassini Project
Published: 2013
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27. Titan’s surface and atmosphere

Author: Máté Ádámkovics, Jason M. Soderblom, and Alexander G. Hayes
Subjects: symbols.namesake, Space and Planetary Science, symbols, Environmental science, Astronomy and Astrophysics, Atmosphere of Titan, Titan (rocket family), Astrobiology
Published: 2016
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28. Observations of Titan’s Northern lakes at 5μm: Implications for the organic cycle and geology

Author: B. Reinhardt, Robert H. Brown, L. A. Soderblom, Katrin Stephan, Bonnie J. Buratti, K. J. Lawrence, Jason M. Soderblom, Roger N. Clark, S. Rodriguez, Christophe Sotin, P. D. Nicholson, Ralf Jaumann, Alexander Hayes, Jason W. Barnes, S. Le Mouélic, Kevin H. Baines, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Centre de physique moléculaire optique et hertzienne (CPMOH), Université Sciences et Technologies - Bordeaux 1 (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), US Geological Survey [Denver], United States Geological Survey [Reston] (USGS), US Geological Survey [Flagstaff], DLR Institute of Planetary Research, German Aerospace Center (DLR), and Cornell University [New York]
Subjects: Synthetic aperture radar, Haze, Titan hydrology, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Atmospheric methane, Organic chemistry, Astronomy and Astrophysics, Atmospheric sciences, Methane, Aerosol, law.invention, symbols.namesake, chemistry.chemical_compound, chemistry, Space and Planetary Science, law, Exobiology, symbols, Atmosphere of Titan, Radar, Titan atmosphere, Titan (rocket family), Titan, Geology
Abstract: International audience; Since Titan entered Northern spring in August 2009, the North Pole has been illuminated allowing observations at optical wavelengths. On June 5, 2010 the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed the Northern Pole area with a pixel size from 3 to 7 km. Since, as we demonstrate, little of the solar flux at 5 μm is scattered by the atmosphere, these observations were obtained at relatively large incidence angles and allowed us to build a mosaic covering an area of more than 500,000 km2 that overlaps and complements observations made by the Synthetic Aperture Radar (SAR) in 2007. We find that there is an excellent correlation between the shape of the radar dark area, known as Ligeia Mare and the VIMS 5-μm dark unit. Matching most of the radar shoreline, the 2010 VIMS observations suggest that the 125,000-km2 surface area of Ligeia Mare measured by RADAR in 2007 has not significantly changed. The VIMS observations complement the radar observations to the west of Ligeia Mare and suggest that Ligeia Mare is connected to Kraken Mare by either a diffuse network similar to a swamp area, or by well-defined, sub-pixel rivers. Considering the results of recent evaporation models of methane, our preferred interpretation of the relative constancy in surface area of Ligeia is that it is principally composed of ethane although we cannot rule out the possibility that methane evaporation is balanced with replenishment by either precipitation or underground seepage. There is also strong correlation between the location of the small radar lakes and the small VIMS 5-μm dark patches. The geographic location of the small lakes are within a VIMS pixel of the SAR location, suggesting that the non-synchronous component of Titan’s spin rate, if it exists, was less than 2.3 × 10−4 deg/day between 2007 and 2010 in agreement with the recent T64 radar observations. These observations question the existence of non-synchronous rotation. Two radar-bright features appear dark at 5-μm. The simplest interpretation is that these are very shallow lakes, less than one meter deep. Three new small lakes, named Freeman, Cardiel, and Towada by the IAU, are found outside of the area mapped with the SAR. A single-scattering model describing reflection of sunlight at 5-μm suggests that the lake surface is mirror-like and that the albedo of the solid surfaces surrounding the lakes is about 8%. These observations together with information of the haze aerosols allow us to show that Titan’s lakes, atmospheric ethane and aerosol haze are smaller carbon reservoirs than Titan’s sand dunes and atmospheric methane. A simple model involving an outburst of methane a few hundreds of Myr ago followed by the dissociation of methane in the atmosphere leading to the formation of the haze particles that constitute the dune fields would be consistent with both the present observations and recent measurements of isotopic ratios in atmospheric methane (Mandt, K.E. et al. [2012]. Astrophys. J. 749(160), 14).
Published: 2012
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29. Titan's fluvial valleys: Morphology, distribution, and spectral properties

Author: Laurence A. Soderblom, Philip D. Nicholson, Roger N. Clark, Kevin H. Baines, Jason W. Barnes, Robert H. Brown, B. J. Buratti, Robert M. Nelson, Christophe Sotin, Ralf Jaumann, Katrin Stephan, Ralph D. Lorenz, Mirjam Langhans, and Jason M. Soderblom
Subjects: Canyon, geography, Spectral signature, geography.geographical_feature_category, Bedrock, Fluvial, Astronomy and Astrophysics, Geophysics, RADAR, symbols.namesake, Tectonics, Volcano, Space and Planetary Science, symbols, VIMS, Groundwater sapping, Cassini, Titan (rocket family), Titan, Geomorphology, Methane, Geology, Valleys
Abstract: Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan's geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200 km and widths of up to 10 km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan's atmospheric windows, as most of them are located on Titan's bright ‘continents’. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at 1.3 μ m in a VIMS false color RGB composite with R: 1.59 / 1.27 μ m , G: 2.03 / 1.27 μ m , and B: 1.27 / 1.08 μ m ; the channels either dissect pure bluish surface units or they are carved into terrain with a mixed spectral signature between bright and bluish surface materials. The global picture of fluvial flows clearly indicates a high diversity of parameters controlling fluvial erosion, such as climatic processes, as well as surface and bedrock types. Recent fluvial activity is very likely in the north polar region in contrast to more arid conditions at lower latitudes and at the south pole of Titan. This divergence is probably an indication of seasonal climatic asymmetries between the hemispheres. However, traces of previous fluvial activity are scattered over all latitudes of Titan, which is indicative of previous climatic conditions with at least episodic rainfall.
Published: 2012
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30. Modeling specular reflections from hydrocarbon lakes on Titan

Author: Bonnie J. Buratti, Kevin H. Baines, Jason M. Soderblom, Robert H. Brown, Roger N. Clark, Philip D. Nicholson, Ralf Jaumann, Caitlin A. Griffith, Laurence A. Soderblom, Katrin Stephan, Christophe Sotin, and Jason W. Barnes
Subjects: Atmospheres, Materials science, Opacity, Infrared observations, business.industry, Scattering, Satellites, Attenuation, Mineralogy, Astronomy and Astrophysics, Surfaces, symbols.namesake, Optics, Atmosphere of Earth, Saturn, Space and Planetary Science, symbols, Specular reflection, Atmosphere of Titan, business, Titan (rocket family), Titan, Refractive index
Abstract: During the 58th close flyby of Titan (T58), the Cassini Visual and Infrared Mapping Spectrometer (VIMS) observed a specular reflection of sunlight from Titan’s Jingpo Lacus through the 5-μm methane window (Stephan, K. et al. [2010]. Geophys. Res. Lett. 37, L07104). The maximum intensity of this reflection is controlled by three basic factors: (1) the shape of the reflecting surface (its overall geometry and roughness), (2) the reflectance of the surface, as controlled by the real refractive index of the material (and that of the atmosphere), and (3) attenuation due to absorption and scattering by atmospheric gases and aerosols along the pathlength. Herein we model the expected intensity of a specular reflection off of a convex mirror-like surface on Titan. We assume the specular reflection is from a body of liquid hydrocarbons on Titan’s surface with optical properties consistent with CH4 and C2H6 with smaller amounts of nitrogen and heavier hydrocarbons (e.g., C3H8) admixed. We assume the 5-μm opacity for the polar atmosphere is a factor of two higher than that of the tropical haze. For the geometry of the T58 observations, our model predicts a maximum I/F = 1-to-5; for a Lambertian surface at normal illumination I/F = 1. The maximum 5-μm intensity observed during T58 was I/F ∼ 2.6, from which we conclude that Jingpo Lacus is filled with a liquid that has a real index of refraction consistent with that of methane–ethane–nitrogen liquid and that the 5-μm atmospheric opacity was τ = 0.5, consistent with the higher particle column expected in the winter polar atmosphere. Future VIMS observations will allow us to refine the refractive index of the liquid in the lakes and to place a quantitative constraint on the ratio of methane to ethane.
Published: 2012
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31. Organic sedimentary deposits in Titan's dry lakebeds: Probable evaporite

Author: G. Vixie, J. Bow, Katrin Stephan, Ralf Jaumann, Laurence A. Soderblom, Christophe Sotin, Philip D. Nicholson, Kevin H. Baines, Jason M. Soderblom, Stéphane Le Mouélic, Robert H. Brown, Sebastien Rodriguez, Jason W. Barnes, Jacob Schwartz, Alexander G. Hayes, Bonnie J. Buratti, Roger N. Clark, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Idaho [Moscow, USA], Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), DLR Institute of Planetary Research, German Aerospace Center (DLR), Planetary Science Institute [Tucson] (PSI), Department of Astronomy [Ithaca], and Cornell University [New York]
Subjects: North pole, 010504 meteorology & atmospheric sciences, Evaporite, Infrared, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, Astrobiology, symbols.namesake, 0103 physical sciences, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Planetary body, Spectrometer, Astronomy and Astrophysics, Mars Exploration Program, geomorphology, lake beds, 13. Climate action, Space and Planetary Science, composition, symbols, Sedimentary rock, Titan (rocket family), Titan, Geology
Abstract: International audience; We report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near Titan's north pole in observations from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). We show evidence that the deposits are evaporitic, making Titan just the third known planetary body with evaporitic processes after Earth and Mars, and is the first that uses a solvent other than water.
Published: 2011
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32. Specular reflection on Titan: Liquids in Kraken Mare

Author: Bonnie J. Buratti, Philip D. Nicholson, Kevin H. Baines, Randolph L. Kirk, Caitlin A. Griffith, Robert M. Nelson, Robert H. Brown, R. N. Clark, Jason W. Barnes, Katrin Stephan, Dyer Lytle, Laurence A. Soderblom, Jason M. Soderblom, Christophe Sotin, and Ralf Jaumann
Subjects: Spacecraft, business.industry, Kraken, law.invention, Astrobiology, symbols.namesake, Wavelength, Geophysics, law, symbols, General Earth and Planetary Sciences, Polar, Specular reflection, Radar, business, Titan (rocket family), Geology
Abstract: [1] After more than 50 close flybys of Titan by the Cassini spacecraft, it has become evident that features similar in morphology to terrestrial lakes and seas exist in Titan's polar regions. As Titan progresses into northern spring, the much more numerous and larger lakes and seas in the north-polar region suggested by Cassini RADAR data, are becoming directly illuminated for the first time since the arrival of the Cassini spacecraft. This allows the Cassini optical instruments to search for specular reflections to provide further confirmation that liquids are present in these evident lakes. On July 8, 2009 Cassini VIMS detected a specular reflection in the north-polar region of Titan associated with Kraken Mare, one of Titan's large, presumed seas, indicating the lake's surface is smooth and free of scatterers with respect to the wavelength of 5 μm, where VIMS detected the specular signal, strongly suggesting it is liquid.
Published: 2010
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33. Geology of the Selk crater region on Titan from Cassini VIMS observations

Author: Jason W. Barnes, Philip D. Nicholson, Bonnie J. Buratti, Katrin Stephan, Christophe Sotin, Kevin H. Baines, Ralf Jaumann, Jason M. Soderblom, Stéphane Le Mouélic, Robert H. Brown, Roger N. Clark, and Laurence A. Soderblom
Subjects: 010504 meteorology & atmospheric sciences, Satellites, Fluvial, 01 natural sciences, Astrobiology, symbols.namesake, Impact crater, Lithosphere, 0103 physical sciences, Ejecta, 010303 astronomy & astrophysics, Geomorphology, 0105 earth and related environmental sciences, Impact processes, Astronomy and Astrophysics, Crust, 15. Life on land, Planetengeologie, Surfaces, Saturn, 13. Climate action, Space and Planetary Science, symbols, Aeolian processes, Ejecta blanket, Geological processes, Titan (rocket family), Titan, Geology
Abstract: Observations of Titan obtained by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) have revealed Selk crater, a geologically young, bright-rimmed, impact crater located ∼800 km north-northwest of the Huygens landing site. The crater rim-crest diameter is ∼90 km; its floor diameter is ∼60 km. A central pit/peak, 20–30 km in diameter, is seen; the ratio of the size of this feature to the crater diameter is consistent with similarly sized craters on Ganymede and Callisto, all of which are dome craters. The VIMS data, unfortunately, are not of sufficient resolution to detect such a dome. The inner rim of Selk crater is fluted, probably by eolian erosion, while the outer flank and presumed ejecta blanket appear dissected by drainages (particularly to the east), likely the result of fluvial erosion. Terracing is observed on the northern and western walls of Selk crater within a 10–15 km wide terrace zone identified in VIMS data; the terrace zone is bright in SAR data, consistent with it being a rough surface. The terrace zone is slightly wider than those observed on Ganymede and Callisto and may reflect differences in thermal structure and/or composition of the lithosphere. The polygonal appearance of the crater likely results from two preexisting planes of weakness (oriented at azimuths of 21° and 122° east of north). A unit of generally bright terrain that exhibits similar infrared-color variation and contrast to Selk crater extends east-southeast from the crater several hundred kilometers. We informally refer to this terrain as the Selk “bench.” Both Selk and the bench are surrounded by the infrared-dark Belet dune field. Hypotheses for the genesis of the optically bright terrain of the bench include: wind shadowing in the lee of Selk crater preventing the encroachment of dunes, impact-induced cryovolcanism, flow of a fluidized-ejecta blanket (similar to the bright crater outflows observed on Venus), and erosion of a streamlined upland formed in the lee of Selk crater by fluid flow. Vestigial circular outlines in this feature just east of Selk’s ejecta blanket suggest that this might be a remnant of an ancient, cratered crust. Evidently the southern margin of the feature has sufficient relief to prevent the encroachment of dunes from the Belet dune field. We conclude that this feature either represents a relatively high-viscosity, fluidized-ejecta flow (a class intermediate to ejecta blankets and long venusian-style ejecta flows) or a streamlined upland remnant that formed downstream from the crater by erosive fluid flow from the west-northwest.
Published: 2010

34. VIMS spectral mapping observations of Titan during the Cassini prime mission

Author: Laurence A. Soderblom, Angioletta Coradini, Priscilla Cerroni, Dale P. Cruikshank, Ralf Jaumann, Caitlin A. Griffith, Katrin Stephan, Vittorio Formisano, Dennis L. Matson, Thomas B. McCord, Jason M. Soderblom, Roger N. Clark, Pierre Drossart, K. M. Pitman, P. D. Nicholson, Bruno Sicardy, Paulo Penteado, Paul O. Hayne, Bonnie J. Buratti, G. Vixie, Yves Langevin, Jean-Pierre Bibring, Christophe Sotin, Stéphane Le Mouélic, Robert H. Brown, Kevin H. Baines, Jason W. Barnes, Sebastien Rodriguez, Robert M. Nelson, Fabrizio Capaccioni, Giancarlo Bellucci, Federico Tosi, University of Idaho [Moscow, USA], Lunar and Planetary Laboratory [University of Arizona] (LPL), University of Arizona, Jet Propulsion Laboratory, California Institute of Technology (JPL), United States Geological Survey, Denver, DLR Institut für Planetenerkundung, Bear Fight Center, Space Science Institute, Winthrop, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), United States Geological Survey, Astrogeology Division, Earth and Space Sciences Department, University of California, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF-Roma), SETI Institute, NASA Ames Research Center, Moffett Field, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Department of Astronomy, Cornell University, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Planetary Science Institute [Tucson] (PSI), Institute of Geological Sciences [Berlin], Department of Earth Sciences [Berlin], Free University of Berlin (FU)-Free University of Berlin (FU), Bear Fight Institute, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), NASA Ames Research Center (ARC), Cornell University [New York], Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy and Astrophysics, Astrobiology, symbols.namesake, Spectral mapping, Space and Planetary Science, symbols, VIMS, Cassini, Titan (rocket family), Titan, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology, Remote sensing
Abstract: International audience; This is a data paper designed to facilitate the use of and comparisons to Cassini/visual and infrared mapping spectrometer (VIMS) spectral mapping data of Saturn's moon Titan. We present thumbnail orthographic projections of flyby mosaics from each Titan encounter during the Cassini prime mission, 2004 July 1 through 2008 June 30. For each flyby we also describe the encounter geometry, and we discuss the studies that have previously been published using the VIMS dataset. The resulting compliation of metadata provides a complementary big-picture overview of the VIMS data in the public archive, and should be a useful reference for future Titan studies.
Published: 2009
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35. Analysis of a cryolava flow-like feature on Titan

Author: Roger N. Clark, Philip D. Nicholson, Sebastien Rodriguez, Jason M. Soderblom, Robert H. Brown, Ralf Jaumann, L. A. Soderblom, Jason W. Barnes, L. Le Corre, S. Le Mouélic, Christophe Sotin, J. P. Combe, Kevin H. Baines, Bonnie J. Buratti, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Synthetic aperture radar, Brightness, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, Spectral line, law.invention, symbols.namesake, law, 0103 physical sciences, Radar, 010303 astronomy & astrophysics, Image resolution, Infrared spectroscopy, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Remote sensing, Spectrometer, Infrared observations, Hyperspectral imaging, Astronomy and Astrophysics, Radar observations, 13. Climate action, Space and Planetary Science, symbols, Titan (rocket family), Titan, Geology
Abstract: This paper reports on the analysis of the highest spatial resolution hyperspectral images acquired by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft during its prime mission. A bright area matches a flow-like feature coming out of a caldera-like feature observed in Synthetic Aperture Radar (SAR) data recorded by the Cassini radar experiment [Lopes et al., 2007. Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper. Icarus 186, 395–412, doi:10.1016/j.icarus.2006.09.006]. In this SAR image, the flow extends about 160 km east of the caldera. The contrast in brightness between the flow and the surroundings progressively vanishes, suggesting alteration or evolution of the composition of the cryolava during the lifetime of the eruptions. Dunes seem to cover part of this flow on its eastern end. We analyze the different terrains using the Spectral Mixing Analysis (SMA) approach of the Multiple-Endmember Linear Unmixing Model (MELSUM, Combe et al., 2008). The study area can be fully modeled by using only two types of terrains. Then, the VIMS spectra are compared with laboratory spectra of known materials in the relevant atmospheric windows (from 1 to 2.78 μm). We considered simple molecules that could be produced during cryovolcanic events, including H2O, CO2 (using two different grain sizes), CH4 and NH3. We find that the mean spectrum of the cryoflow-like feature is not consistent with pure water ice. It can be best fitted by linear combinations of spectra of the candidate materials, showing that its composition is compatible with a mixture of H2O, CH4 and CO2.
Published: 2009
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36. Shoreline features of Titan's Ontario Lacus from Cassini/VIMS observations

Author: Christophe Sotin, Stéphane Le Mouélic, Robert H. Brown, Laurence A. Soderblom, Brian Jackson, Roger N. Clark, Jason M. Soderblom, Bonnie J. Buratti, K. M. Pitman, Ralf Jaumann, Elizabeth P. Turtle, Jason Perry, Kevin H. Baines, P. D. Nicholson, and Jason W. Barnes
Subjects: Shore, Solar System, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Atmospheric correction, Astronomy and Astrophysics, Atmospheric sciences, 01 natural sciences, Astrobiology, symbols.namesake, 13. Climate action, Space and Planetary Science, 0103 physical sciences, symbols, Titan (rocket family), Titan, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract: We analyze observations of Titan's south polar lake Ontario Lacus obtained by Cassini's Visual and Infrared Mapping Spectrometer during the 38th flyby of Titan (T38; 2007 December 5). These near-closest-approach observations have the highest signal-to-noise, the finest spatial resolution, and the least atmospheric influence of any near-infrared lake observation to date. We use the large, spatially flat, and low-albedo interior of Ontario Lacus as a calibration target allowing us to derive an analytical atmospheric correction for emission angle. The dark lake interior is surrounded by two separate annuli that follow the lake interior's contours. The inner annulus is uniformly dark, but not so much as the interior lake, and is generally 5–10 kilometers wide at the lake's southeastern margin. We propose that it represents wet lakebed sediments exposed by either tidal sloshing of the lake or seasonal methane loss leading to lower lake-volume. The exterior annulus is bright and shows a spectrum consistent with a relatively low water-ice content relative to the rest of Titan. It may represent fine-grained condensate deposits from a past era of higher lake level. Together, the annuli seem to indicate that the lake level for Ontario Lacus has changed over time. This hypothesis can be tested with observations scheduled for future Titan flybys.
Published: 2009
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37. The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR

Author: Jason M. Soderblom, Philip D. Nicholson, Jason W. Barnes, Laurence A. Soderblom, Bonnie J. Buratti, Robert H. Brown, Kevin H. Baines, Ralf Jaumann, Daniel W. Mackowski, Roger N. Clark, Christophe Sotin, Randolph L. Kirk, and David J. Mackinnon
Subjects: Fluvial, Astronomy and Astrophysics, Volcanism, Structural basin, symbols.namesake, Tectonics, Saturn, Geologic time scale, Space and Planetary Science, Pluvial, symbols, Geological processes, Impact structure, Titan (rocket family), Titan, Geomorphology, Geology, Remote sensing
Abstract: Joint Cassini VIMS and RADAR SAR data of ∼700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 μm) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100–200 m thick. On its southern edge the basin is ringed by higher (∼1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography evidence a complex set of geological processes (pluvial, fluvial, tectonic, cryovolcanic, impact) that have likely remained active up to very recent geological time (
Published: 2009

38. Fluvial Erosion and Post-erosional Processes on Titan

Author: Ralph D. Lorenz, Mirjam Langhans, Jason W. Barnes, Bonnie J. Buratti, Sebastien Rodriguez, L. A. Soderblom, Dale P. Cruikshank, Ralf Jaumann, Katrin Stephan, Roland Wagner, Thomas B. McCord, Jason M. Soderblom, Phil D. Nicholson, Stéphane Le Mouélic, Robert H. Brown, Kevin H. Baines, Caitlin A. Griffith, Roger N. Clark, Christophe Sotin, Institute of Geological Sciences [Berlin], Department of Earth Sciences [Berlin], Free University of Berlin (FU)-Free University of Berlin (FU), University of Arizona, Université de Nantes (UN), California Institute of Technology (CALTECH), Bear Fight Institute, NASA Ames Research Center (ARC), Department of Astronomy [Ithaca], and Cornell University [New York]
Subjects: 010504 meteorology & atmospheric sciences, Meteorology, Satellites, Ices, Fluvial, surfaces, 01 natural sciences, Sedimentary depositional environment, symbols.namesake, Settling, 0103 physical sciences, Precipitation, 010303 astronomy & astrophysics, Geomorphology, Spectroscopy, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Astronomy and Astrophysics, 15. Life on land, Erosion, 13. Climate action, Space and Planetary Science, Convective storm detection, Physical Sciences, symbols, Alluvium, Titan, Titan (rocket family), Surface runoff, Geology
Abstract: The surface of Titan has been revealed by Cassini observations in the infrared and radar wavelength ranges as well as locally by the Huygens lander instruments. Sand seas, recently discovered lakes, distinct landscapes and dendritic erosion patterns indicate dynamic surface processes. This study focus on erosional and depositional features that can be used to constrain the amount of liquids involved in the erosional process as well as on the compositional characteristics of depositional areas. Fluvial erosion channels on Titan as identified at the Huygens landing site and in RADAR and Visible and Infrared Mapping Spectrometer (VIMS) observations have been compared to analogous channel widths on Earth yielding average discharges of up to 1600 m3/s for short recurrence intervals that are sufficient to move centimeter-sized sediment and significantly higher discharges for long intervals. With respect to the associated drainage areas, this roughly translates to 1–150 cm/day runoff production rates with 10 years recurrence intervals and by assuming precipitation this implies 0.6–60 mm/h rainfall rates. Thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment. During Cassini's T20 fly-by, the VIMS observed an extremely eroded area at 30° W, 7° S with resolutions of up to 500 m/pixel that extends over thousands of square kilometers. The spectral characteristics of this area change systematically, reflecting continuous compositional and/or particle size variations indicative of transported sediment settling out while flow capacities cease. To account for the estimated runoff production and widespread alluvial deposits of fine-grained material, release of area-dependent large fluid volumes are required. Only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these erosional features.
Published: 2008
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39. The identification of liquid ethane in Titan's Ontario Lacus

Author: P. D. Nicholson, Roger N. Clark, L. A. Soderblom, Kevin H. Baines, Christophe Sotin, Ralf Jaumann, Jason W. Barnes, Jason M. Soderblom, Robert H. Brown, and B. J. Buratti
Subjects: Multidisciplinary, Infrared, chemistry.chemical_element, Nitrogen, Liquid methane, Methane, Light hydrocarbons, Astrobiology, On board, symbols.namesake, chemistry.chemical_compound, chemistry, symbols, Atmosphere of Titan, Titan (rocket family), Titan, Cassini spacecraft
Abstract: Saturn's moon Titan was once thought to have global oceans of light hydrocarbons on its surface, but the Cassini spacecraft's 40 close flybys of Titan have shown that no such oceans exist. Yet there are surface features similar to terrestrial lakes and seas. Infrared spectroscopic data from Cassini's 38th flyby reveal a possible explanation. The spectra and physical appearance of Ontario Lacus, a lake-like structure near Titan's south pole, support the idea that it is filled with liquid ethane, probably in solution with methane, nitrogen and other hydrocarbons. Titan was once hypothesized to have global oceans of light hydrocarbons, but it has become clear that none exist. However there are features similar to terrestrial lakes and seas. This paper reports infrared spectroscopic data that strongly indicate that ethane, probably in liquid solution with methane, nitrogen, and other low-molecular-weight hydrocarbons, is contained within Titan's Ontario Lacus. Titan was once thought to have global oceans of light hydrocarbons on its surface1,2,3,4,5, but after 40 close flybys of Titan by the Cassini spacecraft, it has become clear that no such oceans exist6. There are, however, features similar to terrestrial lakes and seas7, and widespread evidence for fluvial erosion8,9, presumably driven by precipitation of liquid methane from Titan’s dense, nitrogen-dominated atmosphere10. Here we report infrared spectroscopic data, obtained by the Visual and Infrared Mapping Spectrometer11 (VIMS) on board the Cassini spacecraft, that strongly indicate that ethane, probably in liquid solution with methane, nitrogen and other low-molecular-mass hydrocarbons, is contained within Titan’s Ontario Lacus.
Published: 2008
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40. A TRANSMISSION SPECTRUM OF TITAN'S NORTH POLAR ATMOSPHERE FROM A SPECULAR REFLECTION OF THE SUN

Author: Sebastien Rodriguez, Roger N. Clark, Jason W. Barnes, Stéphane Le Mouélic, Robert H. Brown, Philip D. Nicholson, Jason M. Soderblom, Kevin H. Baines, Christophe Sotin, Máté Ádámkovics, Bonnie J. Buratti, and T. Appéré
Subjects: Physics, Haze, Scattering, Astronomy, Astronomy and Astrophysics, Spectral line, symbols.namesake, Space and Planetary Science, Planet, symbols, Radiative transfer, Polar, Specular reflection, Titan (rocket family)
Abstract: Cassini/VIMS T85 observations of a solar specular reflection off of Kivu Lacus (87.?4N 241.?1E) provide an empirical transmission spectrum of Titan's atmosphere. Because this observation was acquired from short range (33,000?km), its intensity makes it visible within the 2.0, 2.7, and 2.8 ?m atmospheric windows in addition to the 5 ?m window where all previous specular reflections have been seen. The resulting measurement of the total one-way normal atmospheric optical depth (corresponding to haze scattering plus haze and gas absorption) provides strong empirical constraints on radiative transfer models. Using those models, we find that the total haze column abundance in our observation is 20% higher than the Huygens equatorial value. Ours is the first measurement in the 2-5 ?m wavelength range that probes all the way to the surface in Titan's arctic, where the vast majority of surface liquids are located. The specular technique complements other probes of atmospheric properties such as solar occultations and the direct measurements from Huygens. In breaking the degeneracy between surface and atmospheric absorptions, our measured optical depths will help to drive future calculations of deconvolved surface albedo spectra.
Published: 2013
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41. Geomorphologic Mapping of Titan's Polar Terrains: Constraining Surface Processes and Landscape Evolution

Author: Elizabeth P. Turtle, Samuel Birch, Jason W. Barnes, R. L. Kirk, Alexander G. Hayes, Charlie S. Bristow, Jason D. Hofgartner, Michael Malaska, Jason M. Soderblom, R. M. C. Lopes, Jonathan I. Lunine, Alan D. Howard, R. D. Lorenz, Ellen R. Stofan, William E. Dietrich, Catherine D. Neish, J. M. Moore, Oliver L. White, Charles A. Wood, Marco Mastrogiuseppe, and David A. Williams
Subjects: Titan hydrology, 010504 meteorology & atmospheric sciences, Outcrop, FOS: Physical sciences, 01 natural sciences, symbols.namesake, 0103 physical sciences, Sequence stratigraphy, 010303 astronomy & astrophysics, Geomorphology, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Canyon, geological processes, geography, geography.geographical_feature_category, Landform, Sediment, Astronomy and Astrophysics, Space and Planetary Science, Titan surface, symbols, Polar, Sedimentary rock, Titan, Titan (rocket family), Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract: We present a geomorphologic map of Titan's polar terrains. The map was generated from a combination of Cassini Synthetic Aperture Radar (SAR) and Imaging Science Subsystem imaging products, as well as altimetry, SARTopo and radargrammetry topographic datasets. In combining imagery with topographic data, our geomorphologic map reveals a stratigraphic sequence from which we infer process interactions between units. In mapping both polar regions with the same geomorphologic units, we conclude that processes that formed the terrains of the north polar region also acted to form the landscape we observe at the south. Uniform, SAR-dark plains are interpreted as sedimentary deposits, and are bounded by moderately dissected uplands. These plains contain the highest density of filled and empty lake depressions, and canyons. These units unconformably overlay a basement rock that outcrops as mountains and SAR-bright dissected terrains at various elevations across both poles. All these units are then superposed by surficial units that slope towards the seas, suggestive of subsequent overland transport of sediment. From estimates of the depths of the embedded empty depressions and canyons that drain into the seas, the SAR-dark plains must be >600 m thick in places, though the thickness may vary across the poles. At the lowest elevations of each polar region, there are large seas, which are currently liquid methane/ethane filled at the north and empty at the south. The large plains deposits and the surrounding hillslopes may represent remnant landforms that are a result of previously vast polar oceans, where larger liquid bodies may have allowed for a sustained accumulation of soluble and insoluble sediments, potentially forming layered sedimentary deposits. Coupled with vertical crustal movements, the resulting layers would be of varying solubilities and erosional resistances., 45 pages, 16 figures, 1 table, accepted in Icarus

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