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2. 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

3. Titan: Earth-like on the Outside, Ocean World on the Inside

Author

Samuel Birch, Michael Malaska, Erika Barth, Thomas Cornet, Christophe Sotin, M. Y. Palmer, Rosaly M. C. Lopes, Melissa G. Trainer, Jason W. Barnes, Ella Sciamma-O'Brien, Elizabeth P. Turtle, Andrew J. Coates, Baptiste Journaux, D. Nna-Mvondo, Anezina Solomonidou, Claire Newman, Benoît Seignovert, Paul Corlies, Jordan K. Steckloff, Sarah M. Hörst, Sandrine Vinatier, Ed Sittler, Alexander E. Thelen, Alexander Hayes, Leonardo Regoli, Sébastien Rodriguez, Jennifer Hanley, Jani Radebaugh, Shannon MacKenzie, Conor A. Nixon, Juan M. Lora, E. C. Czaplinski, and Ralph D. Lorenz

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Solar System, Engineering, business.industry, FOS: Physical sciences, Astronomy and Astrophysics, Astrobiology, Atmosphere, Prebiotic chemistry, symbols.namesake, Physics - Atmospheric and Oceanic Physics, Geophysics, Planetary science, Space and Planetary Science, Atmospheric and Oceanic Physics (physics.ao-ph), Earth and Planetary Sciences (miscellaneous), symbols, Earth (chemistry), business, Titan (rocket family), Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

Thanks to the Cassini-Huygens mission, Titan, the pale orange dot of Pioneer and Voyager encounters has been revealed to be a dynamic, hydrologically-shaped, organic-rich ocean world offering unparalleled opportunities to explore prebiotic chemistry. And while Cassini-Huygens revolutionized our understanding of each of the three layers of Titan--the atmosphere, the surface, and the interior--we are only beginning to hypothesize how these realms interact. In this paper, we summarize the current state of Titan knowledge and discuss how future exploration of Titan would address some of the next decade's most compelling planetary science questions. We also demonstrate why exploring Titan, both with and beyond the Dragonfly New Frontiers mission, is a necessary and complementary component of an Ocean Worlds Program that seeks to understand whether habitable environments exist elsewhere in our solar system., Submitted to the PSJ Focus Issue on Ocean World Exploration

Published
2021

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. Morphologic Evidence for Volcanic Craters Near Titan's North Polar Region

Author

Jani Radebaugh and Charles A. Wood

Subjects
geography, geography.geographical_feature_category, Astrobiology, symbols.namesake, Geophysics, Volcano, Impact crater, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), symbols, Caldera, Polar, Titan (rocket family), Geology
Published
2020

7. A global geomorphologic map of Saturn’s moon Titan

Author

M. Florence, R. M. C. Lopes, Alexander G. Hayes, Samuel Birch, Michael Malaska, A. Solomonidou, A. Le Gall, Jani Radebaugh, T. Verlander, David A. Williams, Ashley Schoenfeld, Elizabeth Turtle, S. D. Wall, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, European Space Astronomy Centre (ESAC), European Space Agency (ESA), Department of Astronomy [Ithaca], Cornell University [New York], Arizona State University [Tempe] (ASU), Department of Geological Sciences [BYU], Brigham Young University (BYU), School of Civil Engineering and Environmental Science [Norman] (CEES), University of Oklahoma (OU), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), and 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)

Subjects
Solar System, 010504 meteorology & atmospheric sciences, Equator, Astronomy and Astrophysics, Terrain, Global Map, Geophysics, 15. Life on land, 01 natural sciences, Article, law.invention, Sedimentary depositional environment, Orbiter, symbols.namesake, 13. Climate action, law, [SDU]Sciences of the Universe [physics], 0103 physical sciences, symbols, Titan (rocket family), 010303 astronomy & astrophysics, Relative dating, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Titan has an active methane-based hydrologic cycle1 that has shaped a complex geologic landscape2, making its surface one of most geologically diverse in the Solar System. Despite the differences in materials, temperatures and gravity fields between Earth and Titan, many of their surface features are similar and can be interpreted as products of the same geologic processes3. However, Titan’s thick and hazy atmosphere has hindered the identification of its geologic features at visible wavelengths and the study of its surface composition4. Here we identify and map the major geological units on Titan’s surface using radar and infrared data from the Cassini orbiter spacecraft. Correlations between datasets enabled us to produce a global map even where datasets were incomplete. The spatial and superposition relations between major geological units reveals the likely temporal evolution of the landscape and provides insight into the interacting processes driving its evolution. We extract the relative dating of the various geological units by observing their spatial superposition in order to get information on the temporal evolution of the landscape. The dunes and lakes are relatively young, whereas the hummocky or mountainous terrains are the oldest on Titan. Our results also show that Titan’s surface is dominated by sedimentary or depositional processes with a clear latitudinal variation, with dunes at the equator, plains at mid-latitudes and labyrinth terrains and lakes at the poles.

Published
2020

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

10. Role of fluids in the tectonic evolution of Titan

Author

Zac Yung-Chun Liu, Eric H. Christiansen, Jani Radebaugh, Ron Harris, and Summer Rupper

Subjects
010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, 01 natural sciences, Planform, Methane, Liquid hydrocarbons, Tectonics, chemistry.chemical_compound, symbols.namesake, chemistry, Space and Planetary Science, 0103 physical sciences, symbols, Water cycle, Petrology, Titan (rocket family), 010303 astronomy & astrophysics, Groundwater, Geology, 0105 earth and related environmental sciences
Abstract

Detailed analyses of slopes and arcuate planform morphologies of Titan’s equatorial mountain ridge belts are consistent with formation by contractional tectonism. However, contractional structures in ice require large stresses (4–10 MPa), the sources of which are not likely to exist on Titan. Cassini spacecraft imagery reveals a methane-based hydrological cycle on Titan that likely includes movement of fluids through the subsurface. These crustal liquids may enable contractional tectonic features to form as groundwater has for thrust belts on Earth. In this study, we show that liquid hydrocarbons in Titan’s near subsurface can lead to fluid overpressures that facilitate contractional deformation at smaller stresses (

Published
2016

11. Material transport map of Titan: The fate of dunes

Author

Jani Radebaugh, Elizabeth P. Turtle, Rosaly M. C. Lopes, Michael Malaska, Alexander G. Hayes, and Ralph D. Lorenz

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Equator, Fluvial, Astronomy and Astrophysics, Terrain, Atmospheric sciences, 01 natural sciences, Sink (geography), Latitude, symbols.namesake, Space and Planetary Science, 0103 physical sciences, symbols, Polar, Aeolian processes, Titan (rocket family), 010303 astronomy & astrophysics, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

Using SAR data from Cassini’s RADAR instrument, we examined the orientations of three terrain units on Titan, bright lineated plains, streak-like plains, and linear dunes. From the overall integrated pattern of their orientation, we were able to determine Titan’s global material transport vectors. The analysis indicates that, in both the northern and southern hemispheres, materials from 0 to 35 deg latitude are transported poleward to a belt centred at roughly 35 deg. Materials from 60 to 35 deg latitude are transported equatorward to the belt at roughly 35 deg. Comparison with the global topographical gradient (Lorenz, R.D. et al. [2013]. Icarus 225, 367–377) suggests that fluvial transport is not the dominant process for material transport on Titan, or that it is at least overprinted with another transport mechanism. Our results are consistent with aeolian transport being the dominant mechanism in the equatorial and mid-latitude zones. The zone at 35 deg is thus the ultimate sink for materials from the equator to low polar latitudes; materials making up the equatorial dunes will be transported to the latitude 35-deg belts. Only plains units are observed at latitudes of ∼35 deg; dunes and materials with the spectral characteristics of dunes are not observed at these latitudes. This observation suggests that either dune materials are converted or modified into plains units or that the margins of dunes are transport limited.

Published
2016

12. Alluvial Fan Morphology, distribution and formation on Titan

Author

Alan D. Howard, Jani Radebaugh, J. M. Moore, Samuel Birch, and Alexander G. Hayes

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Atmospheric circulation, Earth science, Alluvial fan, Fluvial, Astronomy and Astrophysics, Mars Exploration Program, 01 natural sciences, symbols.namesake, Space and Planetary Science, 0103 physical sciences, symbols, Aeolian processes, Titan (rocket family), 010303 astronomy & astrophysics, Sediment transport, Geology, 0105 earth and related environmental sciences, Bed load
Abstract

Titan is a hydrologically active world, with dozens of alluvial fans that are evidence of sediment transport from high to low elevations. However, the distribution and requirements for the formation of fans on Titan are not well understood. We performed the first global survey of alluvial fans on Titan using Cassini Synthetic Aperture Radar (SAR) data, which cover 61% of Titan’s surface. We identified 82 fans with areas ranging from 28 km2 to 27,000 km2. A significant fraction (∼60%) of the fans are restricted to latitudes of ±50–80°, suggesting that fluvial sediment transport may have been concentrated in the near-polar terrains in the geologically recent past. The density of fans is also found to be correlated with the latitudes predicted to have the highest precipitation rates by Titan Global Circulation Models. In equatorial regions, observable fans are not generally found in proximity to dune fields. Such observations suggest that sediment transport in these areas is dominated by aeolian transport mechanisms, though with some degree of recent equatorial fluvial activity. The fan area-drainage area relationship on Titan is more similar to that on Earth than on Mars, suggesting that the fans on Titan are smaller than what may be expected, and that the transport of bedload sediment is limited. We hypothesize that this has led to the development of a coarse gravel-lag deposit over much of Titan’s surface. Such a model explains both the morphology of the fans and their latitudinal concentration, yielding insight into the sediment transport regimes that operate across Titan today.

Published
2016

13. Nature, distribution, and origin of Titan’s Undifferentiated Plains

Author

Alexander G. Hayes, Kenneth J. Lawrence, Athena Coustenis, Michael Malaska, A. Le Gall, M. A. Janssen, A. Solomonidou, Ellen R. Stofan, Samuel Birch, Jani Radebaugh, Bryan Stiles, Catherine D. Neish, R. L. Kirk, Elizabeth P. Turtle, K. L. Mitchell, Ashley Schoenfeld, Rosaly M. C. Lopes, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), 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), 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), Department of Physics and Space Sciences [FIT], Florida Institute of Technology [Melbourne], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Department of Astronomy [Ithaca], Cornell University [New York], Department of Geological Sciences [BYU], Brigham Young University (BYU), Astrogeology Science Center [Flagstaff], United States Geological Survey [Reston] (USGS), Department of Earth and Planetary Sciences [UCL/Birkbeck], Birkbeck College [University of London], and California Institute of Technology (CALTECH)-NASA

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], Fluvial, 01 natural sciences, Astrobiology, law.invention, Sedimentary depositional environment, Paleontology, symbols.namesake, Impact crater, law, 0103 physical sciences, Radar, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Astronomy and Astrophysics, 15. Life on land, Radar observations, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 13. Climate action, Space and Planetary Science, symbols, Aeolian processes, Cassini, Sedimentary rock, Geological processes, Titan, Titan (rocket family), Geology
Abstract

The Undifferentiated Plains on Titan, first mapped by Lopes et al. (Lopes, R.M.C. et al., 2010. Icarus, 205, 540–588), are vast expanses of terrains that appear radar-dark and fairly uniform in Cassini Synthetic Aperture Radar (SAR) images. As a result, these terrains are often referred to as “blandlands”. While the interpretation of several other geologic units on Titan – such as dunes, lakes, and well-preserved impact craters – has been relatively straightforward, the origin of the Undifferentiated Plains has remained elusive. SAR images show that these “blandlands” are mostly found at mid-latitudes and appear relatively featureless at radar wavelengths, with no major topographic features. Their gradational boundaries and paucity of recognizable features in SAR data make geologic interpretation particularly challenging. We have mapped the distribution of these terrains using SAR swaths up to flyby T92 (July 2013), which cover >50% of Titan’s surface. We compared SAR images with other data sets where available, including topography derived from the SARTopo method and stereo DEMs, the response from RADAR radiometry, hyperspectral imaging data from Cassini’s Visual and Infrared Mapping Spectrometer (VIMS), and near infrared imaging from the Imaging Science Subsystem (ISS). We examined and evaluated different formation mechanisms, including (i) cryovolcanic origin, consisting of overlapping flows of low relief or (ii) sedimentary origins, resulting from fluvial/lacustrine or aeolian deposition, or accumulation of photolysis products created in the atmosphere. Our analysis indicates that the Undifferentiated Plains unit is consistent with a composition predominantly containing organic rather than icy materials and formed by depositional and/or sedimentary processes. We conclude that aeolian processes played a major part in the formation of the Undifferentiated Plains; however, other processes (fluvial, deposition of photolysis products) are likely to have contributed, possibly in differing proportions depending on location.

Published
2016

14. Alluvial and fluvial fans on Saturn's moon Titan reveal processes, materials and regional geology

Author

Tom G. Farr, Dario Ventra, Jani Radebaugh, Alexander G. Hayes, Samuel Birch, Jason W. Barnes, Philippe Paillou, Alice Le Gall, Rosaly M. C. Lopes, S. D. Wall, Ellen R. Stofan, Ralph D. Lorenz, Zac Yung-Chun Liu, Jonathan I. Lunine, R. L. Kirk, Michael Malaska, Brigham Young University (BYU), Utrecht University [Utrecht], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Astrogeology Science Center [Flagstaff], United States Geological Survey [Reston] (USGS), Department of Astronomy [Ithaca], Cornell University [New York], School of Earth and Space Exploration [Tempe] (SESE), Arizona State University [Tempe] (ASU), University of Idaho [Moscow, USA], 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), Proxemy Research Inc, ASP 2015, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-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), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Regional geology, geography, geography.geographical_feature_category, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010504 meteorology & atmospheric sciences, Landform, Alluvial fan, Fluvial, Geology, Ocean Engineering, 01 natural sciences, Sedimentary depositional environment, symbols.namesake, 13. Climate action, 0103 physical sciences, symbols, Alluvium, Sedimentary rock, Titan (rocket family), 010303 astronomy & astrophysics, Geomorphology, 0105 earth and related environmental sciences, Water Science and Technology
Abstract

International audience; Fans, landforms that record the storage and transport of sediment from uplands to depositional basins, are found on Saturn's moon Titan, a body of significantly different process rates and material compositions from Earth. Images obtained by the Cassini spacecraft's synthetic aperture radar reveal morphologies, roughness, textural patterns and other properties consistent with fan analogues on Earth also viewed by synthetic aperture radar. The observed fan characteristics on Titan reveal some regions of high relative relief and others with gentle slopes over hundreds of kilometres, exposing topographic variations and influences on fan formation. There is evidence for a range of particle sizes across proximal to distal fan regions, from c. 2 cm or more to fine-grained, which can provide details on sedimentary processes. Some features are best described as alluvial fans, which implies their proximity to high-relief source areas, while others are more likely to be fluvial fans, drawing from larger catchment areas and frequently characterized by more prolonged runoff events. The presence of fans corroborates the vast liquid storage capacity of the atmosphere and the resultant episodic behaviour. Fans join the growing list of landforms on Titan derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between these two planetary bodies.

Published
2016

15. Labyrinth terrain on Titan

Author

Rosaly M. C. Lopes, Caitlin Ahrens, Alexander Hayes, Karl L. Mitchell, Meghan Florence, Thomas Cornet, T. Verlander, L. R. Schurmeier, Alice Le Gall, Ashley Schoenfeld, Anezina Solomonidou, Jani Radebaugh, Samuel Birch, Michael A. Janssen, Tom G. Farr, Michael Malaska, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Department of Geological Sciences [BYU], Brigham Young University (BYU), University of Oklahoma (OU), University of California [Los Angeles] (UCLA), University of California, 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), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Department of Astronomy [Ithaca], Cornell University [New York], University of Illinois [Chicago] (UIC), University of Illinois System, and University of Arkansas [Fayetteville]

Subjects
geography, geography.geographical_feature_category, Plateau, 010504 meteorology & atmospheric sciences, Fluvial, Astronomy and Astrophysics, Terrain, 15. Life on land, Karst, 01 natural sciences, Methane, Latitude, Sedimentary depositional environment, chemistry.chemical_compound, symbols.namesake, chemistry, [SDU]Sciences of the Universe [physics], Space and Planetary Science, 0103 physical sciences, symbols, Titan (rocket family), 010303 astronomy & astrophysics, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

International audience; The Cassini/Huygens mission revealed a terrain type on Saturn's moon Titan of dissected, elevated plateaux with a high density of valleys named labyrinth terrain. We define four subtypes of labyrinth terrains: valleyed, polygonal, finely-dissected, and the possible outlier Kronin Labyrinth. We mapped the locations of all labyrinths imaged by Cassini and found they are distributed preferentially at high latitudes. We characterize the labyrinths by morphometric parameters such as intervalley width, valley width, and percent valleys. We find many labyrinths contain closed valleys, which constrains their formation and evolution. We also examine their low microwave emissivity spectral characteristics and find that the labyrinths are consistent with a bulk composition of dominantly organic materials, with some component of water ice – characteristics similar to Titan's undifferentiated plains. Our analyses show that labyrinths are ancient terrains – only the mountains and hummocky terrains are older. This implies that significant organic production occurred early in Titan's history. The organic inventory represented by the labyrinths is estimated to be 15–42% of the solid organic inventory of Titan (or 14–35% of the total surface organics, if the hydrocarbons of the lakes and seas are also included). Our preferred formation of the labyrinth terrains is erosion through dissolution and fluvial processes that dissect the plateau in a manner similar to dissolution geology (karst) on Earth. This scenario requires that the organics that make up the labyrinth terrain be soluble in methane and/or ethane liquids. It also suggests that the origin of the plateaux may have derived from Titan's past chemical production and subsequent depositional record.

Published
2020

16. 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

17. 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

18. The Spectral Nature of Titan's Major Geomorphological Units: Constraints on Surface Composition

Author

Bernard Schmitt, S. D. Wall, S. Philippe, Emmanuel Bratsolis, Christophe Sotin, S. Le Mouélic, Olivier Witasse, A. Solomonidou, Katrin Stephan, Rosaly M. C. Lopes, Charles Elachi, A. Le Gall, Jani Radebaugh, E. Villanueva, A. Anthony Bloom, M. Hirtzig, Robert H. Brown, Athena Coustenis, Kenneth J. Lawrence, Christos Matsoukas, Nicolas Altobelli, M. A. Janssen, Michael Malaska, Pierre Drossart, Sebastien Rodriguez, Jérémy F. Brossier, Ashley Schoenfeld, 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), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, 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), 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), Fondation La main à la pâte, Department of Physics [Athens], National and Kapodistrian University of Athens = University of Athens (NKUA | UoA), Department of Geological Sciences [BYU], Brigham Young University (BYU), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, 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), IMPEC - 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), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Royal Institute of Technology [Stockholm] (KTH ), Department of Earth, Planetary and Space Sciences [Los Angeles] (EPSS), University of California [Los Angeles] (UCLA), University of California-University of California, 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), Agence Spatiale Européenne = European Space Agency (ESA), NASA-California Institute of Technology (CALTECH), 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 (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-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), 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]), National and Kapodistrian University of Athens (NKUA), 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), PLANETO - LATMOS, Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), University of California (UC)-University of California (UC), 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
Synthetic aperture radar, Haze, 010504 meteorology & atmospheric sciences, Spectral response, Atmospheric sciences, Titan geology, 01 natural sciences, Latitude, symbols.namesake, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Radiative transfer, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, [PHYS]Physics [physics], saturnian satellites, Geophysics, 13. Climate action, Space and Planetary Science, radiative transfer, [SDU]Sciences of the Universe [physics], symbols, Evolution theories, Water ice, spectral behavior, geomorphological units, Titan composition, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology
Abstract

We investigate Titan's low‐latitude and midlatitude surface using spectro‐imaging near‐infrared data from Cassini/Visual and Infrared Mapping Spectrometer. We use a radiative transfer code to first evaluate atmospheric contributions and then extract the haze and the surface albedo values of major geomorphological units identified in Cassini Synthetic Aperture Radar data, which exhibit quite similar spectral response to the Visual and Infrared Mapping Spectrometer data. We have identified three main categories of albedo values and spectral shapes, indicating significant differences in the composition among the various areas. We compare with linear mixtures of three components (water ice, tholin‐like, and a dark material) at different grain sizes. Due to the limited spectral information available, we use a simplified model, with which we find that each albedo category of regions of interest can be approximately fitted with simulations composed essentially by one of the three surface candidates. Our fits of the data are overall successful, except in some cases at 0.94, 2.03, and 2.79 μm, indicative of the limitations of our simplistic compositional model and the need for additional components to reproduce Titan's complex surface. Our results show a latitudinal dependence of Titan's surface composition, with water ice being the major constituent at latitudes beyond 30°N and 30°S, while Titan's equatorial region appears to be dominated partly by a tholin‐like or by a very dark unknown material. The albedo differences and similarities among the various geomorphological units give insights on the geological processes affecting Titan's surface and, by implication, its interior. We discuss our results in terms of origin and evolution theories.

Published
2018

21. Global contraction/expansion and polar lithospheric thinning on Titan from patterns of tectonism

Author

Mikael Beuthe, Jason W. Barnes, Jani Radebaugh, Terry Hurford, Bryan Stiles, Casey Cook-Hallett, and Simon A. Kattenhorn

Subjects
Solar System, Equator, Geophysics, Latitude, Tectonics, symbols.namesake, Mountain chain, Space and Planetary Science, Geochemistry and Petrology, Lithosphere, Earth and Planetary Sciences (miscellaneous), symbols, Polar, Titan (rocket family), Geology
Abstract

We investigate the underlying physical processes that govern the formation and evolution of Titan's tectonic features. This is done by mapping mountain chains and hills using Cassini RADAR data obtained during Titan flybys T3 to T69. Our mapping of mountain chains and hills reveals a global pattern: east-west orientations within 30° of the equator and north-south between 60° latitude and the poles. This result makes Titan one of the few solar system bodies where global processes, rather than regional processes, dominate tectonism. After comparison with five global stress models showing theoretical mountain chain orientations, we suggest that either global contraction coupled with spin-up or global expansion coupled with despinning could explain our observations if coupled with a lithosphere thinner in Titan's polar regions.

Published
2015

24. Implications of dune pattern analysis for Titan’s surface history

Author

C. J. Savage, Jani Radebaugh, Ralph D. Lorenz, and Eric H. Christiansen

Subjects
Synthetic aperture radar, education.field_of_study, Population, Pattern analysis, Astronomy and Astrophysics, symbols.namesake, Space and Planetary Science, Long period, symbols, Aeolian processes, Sedimentary rock, Titan (rocket family), education, Geomorphology, Geology, Large size, Remote sensing
Abstract

Analysis of large-scale morphological parameters can reveal the reaction of dunes to changes in atmospheric and sedimentary conditions. Over 7000 dune width and 7000 dune spacing measurements were obtained for linear dunes in regions across Saturn’s moon Titan from images T21, T23, T28, T44 and T48 collected by the Synthetic Aperture RADAR (SAR) aboard the Cassini spacecraft in order to reconstruct the aeolian surface history of Titan. Dunes in the five study areas are all linear in form, with a mean width of 1.3 km and mean crest spacing of 2.7 km, similar to dunes in the African Saharan and Namib deserts on Earth. At the resolution of Cassini SAR, the dunes have the morphology of large linear dunes, and they lack evidence for features of compound or complex dunes. The large size, spacing and uniform morphology are all indicators that Titan’s dunes are mature features, in that they have grown toward a steady state for a long period of time. Dune width decreases to the north, perhaps from increased sediment stabilization caused by a net transport of moisture from south to north, or from increased maturity in dunes to the south. Cumulative probability plots of dune parameters measured at different locations across Titan indicate there is a single population of intermediate-to-large-sized dunes on Titan. This suggests that, unlike analogous dunes in the Namib and Agneitir Sand Seas, dune-forming conditions that generated the current set of dunes were stable and active long enough to erase any evidence of past conditions.

Published
2014

26. Dunes on Saturn’s moon Titan as revealed by the Cassini Mission

Author

Jani Radebaugh

Subjects
geography, geography.geographical_feature_category, Landform, Earth science, Singular form, Equator, Geology, Equinox, Astrobiology, symbols.namesake, symbols, Aeolian processes, Solstice, Titan (rocket family), Earth-Surface Processes
Abstract

Dunes on Titan, a dominant landform comprising at least 15% of the surface, represent the end product of many physical processes acting in alien conditions. Winds in a nitrogen-rich atmosphere with Earth-like pressure transport sand that is likely to have been derived from complex organics produced in the atmosphere. These sands then accumulate into large, planet-encircling sand seas concentrated near the equator. Dunes on Titan are predominantly linear and similar in size and form to the large linear dunes of the Namib, Arabian and Saharan sand seas. They likely formed from wide bimodal winds and appear to undergo average sand transport to the east. Their singular form across the satellite indicates Titan’s dunes may be highly mature, and may reside in a condition of stability that permitted their growth and evolution over long time scales. The dunes are among the youngest surface features, as even river channels do not cut through them. However, reorganization time scales of large linear dunes on Titan are likely tens of thousands of years. Thus, Titan’s dune forms may be long-lived and yet be actively undergoing sand transport. This work is a summary of research on dunes on Titan after the Cassini Prime and Equinox Missions (2004–2010) and now during the Solstice Mission (to end in 2017). It discusses results of Cassini data analysis and modeling of conditions on Titan and it draws comparisons with observations and models of linear dune formation and evolution on Earth.

Published
2013

27. Cryovolcanism on Titan: New results from Cassini RADAR and VIMS

Author

Michael Malaska, S. D. Wall, Jeffrey S. Kargel, Ellen R. Stofan, Jonathan I. Lunine, Rosaly M. C. Lopes, Lauren Wye, M. A. Janssen, Jani Radebaugh, A. Legall, Jason W. Barnes, Catherine D. Neish, Karl L. Mitchell, Charles A. Wood, Alexander G. Hayes, and Randolph L. Kirk

Subjects
Synthetic aperture radar, 010504 meteorology & atmospheric sciences, biology, Patera, biology.organism_classification, 01 natural sciences, law.invention, Astrobiology, symbols.namesake, Geophysics, Impact crater, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, law, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), symbols, Radiometry, Radar, Titan (rocket family), 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

[1] The existence of cryovolcanic features on Titan has been the subject of some controversy. Here we use observations from the Cassini RADAR, including Synthetic Aperture Radar (SAR) imaging, radiometry, and topographic data as well as compositional data from the Visible and Infrared Mapping Spectrometer (VIMS) to reexamine several putative cryovolcanic features on Titan in terms of likely processes of origin (fluvial, cryovolcanic, or other). We present evidence to support the cryovolcanic origin of features in the region formerly known as Sotra Facula, which includes the deepest pit so far found on Titan (now known as Sotra Patera), flow-like features (Mohini Fluctus), and some of the highest mountains on Titan (Doom and Erebor Montes). We interpret this region to be a cryovolcanic complex of multiple cones, craters, and flows. However, we find that some other previously supposed cryovolcanic features were likely formed by other processes. Cryovolcanism is still a possible formation mechanism for several features, including the flow-like units in Hotei Regio. We discuss implications for eruption style and composition of cryovolcanism on Titan. Our analysis shows the great value of combining data sets when interpreting Titan's geology and in particular stresses the value of RADAR stereogrammetry when combined with SAR imaging and VIMS.

Published
2013

28. 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

29. Titan’s surface at 2.18-cm wavelength imaged by the Cassini RADAR radiometer: Results and interpretations through the first ten years of observation

Author

Stephen Keihm, Mathieu Choukroun, Alexander G. Hayes, Rosaly M. C. Lopes, Marco Mastrogiuseppe, A. Solomonidou, Ralph D. Lorenz, A. Le Gall, Jani Radebaugh, C. Leyrat, Michael Malaska, Pierre Encrenaz, K. L. Mitchell, Catherine D. Neish, M. A. Janssen, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, 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 Astronomy [Ithaca], Cornell University [New York], Department of Physics and Space Sciences [FIT], Florida Institute of Technology [Melbourne], Department of Geological Sciences [BYU], Brigham Young University (BYU), 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), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), 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 de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Ingegneria dell'Informazione, Elettronica e Telecomunicazioni [Roma] (DIET), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], NASA-California Institute of Technology (CALTECH), École normale supérieure - Paris (ENS-PSL), and Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA)

Subjects
Brightness, 010504 meteorology & atmospheric sciences, Satellites, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, Latitude, radio observations, satellites, composition, satellites, surfaces, symbols.namesake, Radio observations, 0103 physical sciences, Emissivity, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing, Radiometer, Scattering, Astronomy and Astrophysics, Surface, Surfaces, Wavelength, 13. Climate action, Space and Planetary Science, Brightness temperature, symbols, Titan (rocket family), Titan, Geology, Composition
Abstract

International audience; A comprehensive calibration and mapping of the thermal microwave emission from Titan’s surface is reported based on radiometric data obtained at 2.18-cm wavelength by the passive radiometer included in the Cassini RADAR instrument. Compared to previous work, the present results incorporate the much larger data set obtained in the approximately ten years following Saturn Orbit Insertion. Brightness temperature data including polarization were accumulated by segments in Titan passes from Ta (October 2004) through T98 (February 2014). The observational segments were analyzed to produce a mosaic of effective dielectric constant based on the measurement of thermal polarization covering 76% of the surface, and brightness temperature at normal incidence covering Titan’s entire surface. As part of the mosaicking process we also solved for the seasonal variation of physical temperature with latitude, which we found to be smaller by a factor of 0.87 ± 0.05 in relative amplitude compared to that reported in the thermal infrared by Cassini’s Composite Infrared Spectrometer (CIRS). We used the equatorial temperature obtained by the Huygens probe and the seasonal dependence with latitude from CIRS to convert the brightness mosaic to absolute emissivity, from which we could infer global thermophysical properties of the surface in combination with the dielectric mosaic. We see strong evidence for subsurface (volume) scattering as a dominant cause of the radar reflectivity in bright regions, and elsewhere a surface composition consistent with the slow deposition and processing of organic compounds from the atmosphere. The presence of water ice in the near subsurface is strongly indicated by the high degree of volume scattering observed in radar-bright regions (e.g., Hummocky/mountainous terrains) constituting ∼ 10% of Titan’s surface. A thermal analysis allowed us to infer a mean 2.18-cm emission depth in the range 40 to 100 cm for the dominant radar-dark terrains (the remainder of Titan’s surface) at all latitudes of Titan, consistent with the deposition and possible processing and redistribution of tholin-like atmospheric photochemical products.

Published
2016

30. THE LINEAR DUNES AND SAND SEAS OF TITAN

Author

Jani Radebaugh and Bradley Bishop

Subjects
symbols.namesake, symbols, Geotechnical engineering, Titan (rocket family), Geomorphology, Geology
Published
2016

31. Geomorphologic mapping of the Menrva region of Titan using Cassini RADAR data

Author

Rosaly M. C. Lopes, Jani Radebaugh, David A. Williams, and Ellen R. Stofan

Subjects
Astronomy and Astrophysics, Geologic map, Fault scarp, law.invention, Tectonics, symbols.namesake, Impact crater, Space and Planetary Science, law, Radar imaging, symbols, Radar, Titan (rocket family), Ejecta, Geomorphology, Geology, Remote sensing
Abstract

We made a detailed geomorphologic map of the Menrva region of Titan, using Cassini RADAR data as our map base. Using similar techniques and approaches that were applied to mapping Magellan radar images of Venus, and earlier, more generalized Titan maps, we were able to define and characterize 10 radar morphologic units, along with inferred dunes and fluvial channels, from the RADAR data. Structural features, such as scarps, ridges, and lineaments were also identified. Using principles of superposition, cross-cutting, and embayment relations we created a sequence of map units for this region. We interpret Menrva to be a 440 km wide degraded impact basin, in agreement with earlier studies by Elachi et al. (Elachi, C. et al. [2006]. Nature 441, 709–713) and Wood et al. (Wood, C.A., Lorenz, R., Kirk, R., Lopes, R., Mitchell, K., Stofan, E., and the Cassini RADAR Team [2010]. Icarus 206, 334–344), and identify it as the oldest feature in the map region. Exogenic processes including hydrocarbon fluid channelization forming the Elivagar Flumina channel network and dune fields resulting from aeolian activity are the current geologic processes dominating our map area, and these processes have contributed to the erosion of the crater’s ejecta field. There is evidence of multiple episodes of channel formation, erosion and burial by aeolian deposits, as observed elsewhere on Titan by e.g., Barnes et al. (Barnes, J.W. et al. [2005]. Icarus 195, 400–414). Channel outflow regions have morphologies suggestive of streams formed by flash floods, and dune fields are small and restricted rather than forming large dune seas, consistent with a desert-like environment for this region with low supply of hydrocarbon particles, also consistent with other studies by e.g., Lorenz et al. (Lorenz, R.D. et al. [2008a]. Planet. Space Sci. 56, 1132–1144). There is no evidence of cryovolcanism or non-impact-related tectonic activity in the Menrva region, although this region is too small to infer anything about the roles of these processes elsewhere on Titan. This work suggests detailed geomorphologic mapping can confidently be applied to Cassini RADAR data, and we suggest that more extensive mapping should be done using RADAR, ISS, and VIMS data geographically distributed across Titan to assess its usefulness for a future combined RADAR–ISS–VIMS-based global geologic map.

Published
2011

32. Regional geomorphology and history of Titan’s Xanadu province

Author

S. D. Wall, Alexander G. Hayes, Ellen R. Stofan, Jonathan I. Lunine, Flora Paganelli, R. L. Kirk, Charles A. Wood, P. Valora, Rosaly M. C. Lopes, M. A. Janssen, A. Legall, Jani Radebaugh, Ralph D. Lorenz, Howard A. Zebker, Tom G. Farr, K. L. Mitchell, Richard West, E. L. Schaller, Giuseppe Mitri, Bryan Stiles, and Lauren Wye

Subjects
geography, geography.geographical_feature_category, Bedrock, Geochemistry, Astronomy and Astrophysics, Terrain, Crust, Lineation, symbols.namesake, Mountainous terrain, Impact crater, Space and Planetary Science, Lithosphere, symbols, Titan (rocket family), Geology
Abstract

Titan’s enigmatic Xanadu province has been seen in some detail with instruments from the Cassini spacecraft. The region contains some of the most rugged, mountainous terrain on Titan, with relief over 2000 m. Xanadu contains evolved and integrated river channels, impact craters, and dry basins filled with smooth, radar-dark material, perhaps sediments from past lake beds. Arcuate and aligned mountain chains give evidence of compressional tectonism, yet the overall elevation of Xanadu is puzzlingly low compared to surrounding sand seas. Lineations associated with mountain fronts and valley floors give evidence of extension that probably contributed to this regional lowering. Several locations on Xanadu’s western and southern margins contain flow-like features that may be cryovolcanic in origin, perhaps ascended from lithospheric faults related to regional downdropping late in its history. Radiometry and scatterometry observations are consistent with a water–ice or water–ammonia–ice composition to its exposed, eroded, fractured bedrock; both microwave and visible to near-infrared (v-nIR) data indicate a thin overcoating of organics, likely derived from the atmosphere. We suggest Xanadu is one of the oldest terrains on Titan and that its origin and evolution have been controlled and shaped by compressional and then extensional tectonism in the icy crust and ongoing erosion by methane rainfall.

Published
2011

33. Extraterrestrial dunes: An introduction to the special issue on planetary dune systems

Author

Mary Bourke, Eric J. R. Parteli, Jani Radebaugh, James R. Zimbelman, Nicholas Lancaster, and Lori K. Fenton

Subjects
Bedform, Planetary surface, biology, Earth science, Venus, Mars Exploration Program, biology.organism_classification, Planetary missions, Astrobiology, symbols.namesake, Extraterrestrial life, symbols, Aeolian processes, Titan (rocket family), Geology, Earth-Surface Processes
Abstract

Aeolian dune fields have been described on Earth, Mars, Venus and Titan. The plethora of data returned from recent planetary missions has enabled a new era in planetary geomorphic studies. Much of our understanding of planetary dune systems comes from the application of Earth analogs, wind tunnel experiments and modeling studies. Despite the range of atmospheric pressures, composition and gravity, many of the dune forms on extraterrestrial surfaces are similar to those on Earth, although some have notable differences in bedform scale and composition. As an introduction to the special issue on planetary dune systems this paper summarizes the current state of knowledge of planetary dune studies and highlights outstanding questions that require further investigation.

Published
2010

34. Distribution and interplay of geologic processes on Titan from Cassini radar data

Author

M. A. Janssen, L. A. Soderblom, Flora Paganelli, A. Legall, Ralph D. Lorenz, Jani Radebaugh, Jonathan I. Lunine, Philip S. Callahan, Karl L. Mitchell, J. Craig, Bryan Stiles, S. D. Wall, R.J. Ollerenshaw, Ellen R. Stofan, R. Peckyno, Charles A. Wood, Alexander G. Hayes, Randolph L. Kirk, Robert West, P. Valora, Rosaly M. C. Lopes, Tom G. Farr, Y. Anderson, Giuseppe Mitri, and Lauren Wye

Subjects
Fluvial, Astronomy and Astrophysics, Latitude, Tectonics, symbols.namesake, Paleontology, Impact crater, Space and Planetary Science, Pluvial, Radar imaging, symbols, Aeolian processes, Titan (rocket family), Geology, Remote sensing
Abstract

The Cassini Titan Radar Mapper is providing an unprecedented view of Titan’s surface geology. Here we use Synthetic Aperture Radar (SAR) image swaths (Ta–T30) obtained from October 2004 to December 2007 to infer the geologic processes that have shaped Titan’s surface. These SAR swaths cover about 20% of the surface, at a spatial resolution ranging from ∼350 m to ∼2 km. The SAR data are distributed over a wide latitudinal and longitudinal range, enabling some conclusions to be drawn about the global distribution of processes. They reveal a geologically complex surface that has been modified by all the major geologic processes seen on Earth – volcanism, tectonism, impact cratering, and erosion and deposition by fluvial and aeolian activity. In this paper, we map geomorphological units from SAR data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of Titan’s surface. We find that dunes and hummocky and mountainous terrains are more widespread than lakes, putative cryovolcanic features, mottled plains, and craters and crateriform structures that may be due to impact. Undifferentiated plains are the largest areal unit; their origin is uncertain. In terms of latitudinal distribution, dunes and hummocky and mountainous terrains are located mostly at low latitudes (less than 30°), with no dunes being present above 60°. Channels formed by fluvial activity are present at all latitudes, but lakes are at high latitudes only. Crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude, but the well-preserved impact craters are all located at low latitudes, possibly indicating that more resurfacing has occurred at higher latitudes. Cryovolcanic features are not ubiquitous, and are mostly located between 30° and 60° north. We examine temporal relationships between units wherever possible, and conclude that aeolian and fluvial/pluvial/lacustrine processes are the most recent, while tectonic processes that led to the formation of mountains and Xanadu are likely the most ancient.

Published
2010

35. Determining Titan surface topography from Cassini SAR data

Author

Karl L. Mitchell, Ralph D. Lorenz, Bryan Stiles, Michael Janssen, William T. K. Johnson, David M. Bates, F. J. Pelletier, Jonathan I. Lunine, Randolph L. Kirk, Yonggyu Gim, Scott Hensley, Philip S. Callahan, Stephen D. Wall, Jani Radebaugh, Chandini Veeramacheneni, Richard West, Howard A. Zebker, Alexander G. Hayes, and Charles A. Wood

Subjects
Synthetic aperture radar, Northern Hemisphere, Astronomy and Astrophysics, Global Map, Context (language use), symbols.namesake, Impact crater, Space and Planetary Science, Nadir, symbols, Altimeter, Titan (rocket family), Geology, Remote sensing
Abstract

A technique, referred to as SARTopo, has been developed for obtaining surface height estimates with 10 km horizontal resolution and 75 m vertical resolution of the surface of Titan along each Cassini Synthetic Aperture Radar (SAR) swath. We describe the technique and present maps of the co-located data sets. A global map and regional maps of Xanadu and the northern hemisphere hydrocarbon lakes district are included in the results. A strength of the technique is that it provides topographic information co-located with SAR imagery. Having a topographic context vastly improves the interpretability of the SAR imagery and is essential for understanding Titan. SARTopo is capable of estimating surface heights for most of the SAR-imaged surface of Titan. Currently nearly 30% of the surface is within 100 km of a SARTopo height profile. Other competing techniques provide orders of magnitude less coverage. We validate the SARTopo technique through comparison with known geomorphological features such as mountain ranges and craters, and by comparison with co-located nadir altimetry, including a 3000 km strip that had been observed by SAR a month earlier. In this area, the SARTopo and nadir altimetry data sets are co-located tightly (within 5–10 km for one 500 km section), have similar resolution, and as expected agree closely in surface height. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and precision of both techniques.

Published
2009

36. Fluvial channels on Titan: Initial Cassini RADAR observations

Author

Rosaly M. C. Lopes, Jani Radebaugh, Gian Gabriele Ori, Ellen R. Stofan, Hideyaki Miyamoto, Bryan Stiles, Charles A. Wood, Stephen D. Wall, Randolph L. Kirk, Ralph D. Lorenz, Melissa J. Myers, Karl L. Mitchell, Flora Paganelli, Jonathan I. Lunine, and L. A. Soderblom

Subjects
Brightness, Fluvial, Astronomy and Astrophysics, Geophysics, Methane, law.invention, Latitude, symbols.namesake, chemistry.chemical_compound, chemistry, Space and Planetary Science, law, Radar imaging, symbols, Polar, Radar, Titan (rocket family), Geomorphology, Geology
Abstract

Cassini radar images show a variety of fluvial channels on Titan's surface, often several hundreds of kilometers in length. Some (predominantly at low- and mid-latitude) are radar-bright and braided, resembling desert washes where fines have been removed by energetic surface liquid flow, presumably from methane rainstorms. Others (predominantly at high latitudes) are radar-dark and meandering and drain into or connect polar lakes, suggesting slower-moving flow depositing fine-grained sediments. A third type, seen predominantly at mid- and high latitudes, have radar brightness patterns indicating topographic incision, with valley widths of up to 3 km across and depth of several hundred meters. These observations show that fluvial activity occurs at least occasionally at all latitudes, not only at the Huygens landing site, and can produce channels much larger in scale than those observed there. The areas in which channels are prominent so far amount to about 1% of Titan's surface, of which only a fraction is actually occupied by channels. The corresponding global sediment volume inferred is not enough to account for the extensive sand seas. Channels observed so far have a consistent large-scale flow pattern, tending to flow polewards and eastwards.

Published
2008

37. Mountains on Titan observed by Cassini Radar

Author

Rosaly M. C. Lopes, Stephen D. Wall, Jani Radebaugh, Jonathan I. Lunine, Ellen R. Stofan, Randolph L. Kirk, and Ralph D. Lorenz

Subjects
Maximum slope, Fluvial, Astronomy and Astrophysics, Erosion rate, Extensional definition, law.invention, Astrobiology, symbols.namesake, Space and Planetary Science, law, symbols, Radar, Titan (rocket family), Ejecta, Surface runoff, Geomorphology, Geology
Abstract

The Cassini Titan Radar mapper has observed elevated blocks and ridge-forming block chains on Saturn's moon Titan demonstrating high topography we term “mountains.” Summit flanks measured from the T3 (February 2005) and T8 (October 2005) flybys have a mean maximum slope of 37° and total elevations up to 1930 m as derived from a shape-from-shading model corrected for the probable effects of image resolution. Mountain peak morphologies and surrounding, diffuse blankets give evidence that erosion has acted upon these features, perhaps in the form of fluvial runoff. Possible formation mechanisms for these mountains include crustal compressional tectonism and upthrusting of blocks, extensional tectonism and formation of horst-and-graben, deposition as blocks of impact ejecta, or dissection and erosion of a preexisting layer of material. All above processes may be at work, given the diversity of geology evident across Titan's surface. Comparisons of mountain and blanket volumes and erosion rate estimates for Titan provide a typical mountain age as young as 20–100 million years.

Published
2007

38. Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

Author

Jonathan I. Lunine, Michael Janssen, Rosaly M. C. Lopes, Philip D. Nicholson, Ellen R. Stofan, Laurence A. Soderblom, Jason W. Barnes, Kevin H. Baines, Ralf Jaumann, Bonnie J. Buratti, Roger N. Clark, Ralph D. Lorenz, Thomas B. McCord, Dale P. Cruikshank, Charles Elachi, Jeffrey A. Anderson, T. Sucharski, Erich Karkoschka, Christophe Sotin, Randolph L. Kirk, Martin G. Tomasko, Jani Radebaugh, Stephen D. Wall, Stéphane Le Mouélic, Robert H. Brown, Janet M. Barrett, and Bashar Rizk

Subjects
Synthetic aperture radar, Dunes, Titriles, Tholin, Infrared, Mineralogy, Spectral line, law.invention, symbols.namesake, Coatings, law, Radar imaging, VIMS, Radar, DISR, Remote sensing, Aerosols, Radiometer, Astronomy and Astrophysics, Mantles, Hydrocarbons, Aerosol, Water ice, Space and Planetary Science, symbols, Titan, Substrate, Titan (rocket family), Geology, SAR
Abstract

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as “brown” and “blue” in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 μm). In such composites bluer materials exhibit higher reflectance at 1.3 μm and lower at 1.6 and 2.0 μm. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001–0.01 μm/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

Published
2007

39. Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper

Author

G. Boubin, Michael Allison, Ellen R. Stofan, Charles Elachi, G. Hamilton, Steven J. Ostro, L. Roth, Randolph L. Kirk, William T. K. Johnson, Stephen D. Wall, Y. Anderson, S. Shaffer, Roberto Seu, Philip S. Callahan, Lauren Wye, R. Boehmer, Bryan Stiles, Gian Gabriele Ori, Jani Radebaugh, Karl L. Mitchell, Giovanni Picardi, Howard A. Zebker, Laurence A. Soderblom, Duane O. Muhleman, Richard West, S. Vetrella, Enrico Flamini, R. D. Lorenz, Roberto Orosei, Andrew Dominic Fortes, Jonathan I. Lunine, Yonggyu Gim, K. Kelleher, L. E. Robshaw, Catherine D. Neish, E. Reffet, Pierre Encrenaz, Scott Hensley, Flora Paganelli, Michael Janssen, Rosaly M. C. Lopes, Francesco Posa, Charles A. Wood, G. Francescetti, Jet Propulsion Laboratory, California Institute of Technology (JPL), Proxemy Research, Bowie, Lunar and Planetary Laboratory [University of Arizona] (LPL), University of Arizona, Istituto di Fisica dello Spazio Interplanetario (IFSI), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), US Geological Survey, Flagstaff, Wheeling Jesuit University, Environmental Sciences Department, Lancaster University, University College of London [London] (UCL), Goddard Institute for Space Studies, National Aeronautics and Space Administration New York, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), 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 de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Instrumentation et télédétection, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Agenzia Spaziale Italiana (ASI), Facoltá di Ingegneria, Geological and Planetary Sciences, California Institute of Technology, Pasadena, International Research School of Planetary Sciences, Dipartimento di Scienze, Università d'Annunzio, Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), Universitá La Sapienza, INFM and Dipartimento Interateneo di Fisica, and Stanford University

Subjects
Synthetic aperture radar, Solar System, geography, satellites of saturn, titan, volcanism, geography.geographical_feature_category, biology, Lava, Astronomy and Astrophysics, Venus, biology.organism_classification, Astrobiology, law.invention, symbols.namesake, Volcano, Space and Planetary Science, law, Radar imaging, symbols, Radar, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Titan (rocket family), Geology
Abstract

International audience; The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar images of Titan's surface during four fly-bys during the mission's first year. These images show that Titan's surface is very complex geologically, showing evidence of major planetary geologic processes, including cryovolcanism. This paper discusses the variety of cryovolcanic features identified from SAR images, their possible origin, and their geologic context. The features which we identify as cryovolcanic in origin include a large (180 km diameter) volcanic construct (dome or shield), several extensive flows, and three calderas which appear to be the source of flows. The composition of the cryomagma on Titan is still unknown, but constraints on rheological properties can be estimated using flow thickness. Rheological properties of one flow were estimated and appear inconsistent with ammonia-water slurries, and possibly more consistent with ammonia-water-methanol slurries. The extent of cryovolcanism on Titan is still not known, as only a small fraction of the surface has been imaged at sufficient resolution. Energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of Titan.

Published
2007

40. Radar scattering of linear dunes and mega-yardangs: Application to Titan

Author

Philippe Paillou, Jani Radebaugh, Stephen D. Wall, Benoît Seignovert, ASP 2016, 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), Université de Bordeaux (UB)-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), Department of Geological Sciences [BYU], Brigham Young University (BYU), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), CNES, and DLR TerraSAR-X proposal GEO1970

Subjects
Radar cross-section, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, 01 natural sciences, law.invention, symbols.namesake, law, Radar imaging, 0103 physical sciences, Radar, 010303 astronomy & astrophysics, Geomorphology, Yardang, 0105 earth and related environmental sciences, Remote sensing, Earth and Planetary Astrophysics (astro-ph.EP), geography, geography.geographical_feature_category, Landform, Astronomy and Astrophysics, Radar observations, Space and Planetary Science, symbols, Aeolian processes, Radiometry, Titan (rocket family), Titan, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

The Ku-band (13.8 GHz - 2.2 cm) RADAR instrument onboard the Cassini-Huygens spacecraft has revealed the richness of the surface of Titan, as numerous seas, lakes, rivers, cryo-volcanic flows and vast dune fields have been discovered. Linear dunes are a major geomorphological feature present on Titan, covering up to 17% of its surface, mainly in equatorial regions. However, the resolution of the RADAR instrument is not good enough to allow a detailed study of the morphology of these features. In addition, other linear wind-related landforms, such as mega-yardangs (linear wind-abraded ridges formed in cohesive rocks), are likely to present a comparable radar signature that could be confused with the one of dunes. We conducted a comparative study of the radar radiometry of both linear dunes and mega-yardangs, based on representative terrestrial analogues: the linear dunes located in the Great Sand Sea in western Egypt and in the Namib Desert in Namibia, and the mega-yardangs observed in the Lut Desert in eastern Iran and in the Borkou Desert in northern Chad. We analysed the radar scattering of both terrestrial linear dunes and mega-yardangs, using high-resolution radar images acquired by the X-band (9.6 GHz - 3.1 cm) sensor of the TerraSAR-X satellite. Variations seen in the radar response of dunes are the result of a contrast between the dune and interdune scattering, while for mega-yardangs these variations are the result of a contrast between ridges and erosion valleys. We tested a simple surface scattering model, with parameters derived from the local topography and surface roughness estimates, to accurately reproduce the radar signal variations for both landforms. It appears that we can discriminate between two types of dunes - bare interdunes as in Egypt and sand-covered interdunes as in Namibia, and between two types of mega-yardangs - young yardangs..., Comment: In press in Icarus (August 2015)

Published
2015

41. Production and global transport of Titan’s sand particles

Author

Clayton K. Chandler, Jason W. Barnes, Jani Radebaugh, Alexander G. Hayes, K. Arnold, and Ralph D. Lorenz

Subjects
symbols.namesake, Planetary science, Barchan, Earth science, symbols, Fluvial, Structural basin, Titan (rocket family), Geomorphology, Lithification, Geology, Southwest Africa
Abstract

Previous authors have suggested that Titan’s individual sand particles form by either sintering or by lithification and erosion. We suggest two new mechanisms for the production of Titan’s organic sand particles that would occur within bodies of liquid: flocculation and evaporitic precipitation. Such production mechanisms would suggest discrete sand sources in dry lakebeds. We search for such sources, but find no convincing candidates with the present Cassini Visual and Infrared Mapping Spectrometer coverage. As a result we propose that Titan’s equatorial dunes may represent a single, global sand sea with west-to-east transport providing sources and sinks for sand in each interconnected basin. The sand might then be transported around Xanadu by fast-moving Barchan dune chains and/or fluvial transport in transient riverbeds. A river at the Xanadu/Shangri-La border could explain the sharp edge of the sand sea there, much like the Kuiseb River stops the Namib Sand Sea in southwest Africa on Earth. Future missions could use the composition of Titan’s sands to constrain the global hydrocarbon cycle.

Published
2015

42. The Sand Seas of Titan: Cassini RADAR Observations of Longitudinal Dunes

Author

Howard A. Zebker, L. Roth, Ralph D. Lorenz, Bryan Stiles, Charles Elachi, Y. Anderson, Ellen R. Stofan, Roberto Seu, K. Kelleher, Giovanni Picardi, Gian Gabriele Ori, K. L. Mitchell, E. Reffet, Duane O. Muhleman, Jonathan I. Lunine, Jani Radebaugh, Enrico Flamini, G. Boubin, Yonggyu Gim, Lauren Wye, S. D. Wall, G. Francescetti, Robert West, Matthew A. Allison, S. Vetrella, Rosaly M. C. Lopes, G. Hamilton, Philip S. Callahan, Laurence A. Soderblom, R. Boehmer, S. Shaffer, Steven J. Ostro, Randolph L. Kirk, Pierre Encrenaz, Scott Hensley, M. A. Janssen, Flora Paganelli, William L. Johnson, Francesco Posa, Charles A. Wood, R. D., Lorenz, S., Wall, J., Radebaugh, G., Boubin, E., Reffet, M., Janssen, E., Stofan, R., Lope, R., Kirk, C., Elachi, J., Lunine, K., Mitchell, F., Paganelli, L., Soderblom, C., Wood, L., Wye, H., Zebker, Y., Anderson, S., Ostro, M., Allison, R., Boehmer, P., Callahan, P., Encrenaz, G. G., Ori, Franceschetti, Giorgio, Y., Gim, G., Hamilton, S., Hensley, W., Johnson, K., Kelleher, D., Muhleman, G., Picardi, F., Posa, L., Roth, R., Seu, S., Shaffer, B., Stile, Vetrella, Sergio, E., Flamini, R., West, Lunar and Planetary Laboratory [University of Arizona] (LPL), University of Arizona, Jet Propulsion Laboratory, California Institute of Technology (JPL), Proxemy Research, Bowie, US Geological Survey, Flagstaff, Planetary Science Institute, Tucson, AZ 85719, USA and Wheeling Jesuit College, Wheeling, Stanford University, Goddard Institute for Space Studies, National Aeronautics and Space Administration New York, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), 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 de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Instrumentation et télédétection, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), International Research School of Planetary Sciences, Dipartimento di Scienze, Università d'Annunzio, Facoltá di Ingegneria, Geological and Planetary Sciences, California Institute of Technology, Pasadena, Universitá La Sapienza, Istituto Nazionale per la Fisica della Materia (INFM) and Dip. Interateneo di Fisica, and Agenzia Spaziale Italiana (ASI)

Subjects
Geologic Sediments, Radar, Multidisciplinary, Extraterrestrial Environment, Titan moon, Wind, Hydrocarbons, Radar observations, Radar imaging, Wavelength, symbols.namesake, Saturn, Surface winds, symbols, Cassini, Particle Size, Spacecraft, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Titan (rocket family), Methane, Geomorphology, Geology, Remote sensing
Abstract

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

Published
2006

43. Lava lakes on Io: observations of Io's volcanic activity from Galileo NIMS during the 2001 fly-bys

Author

Peter J. Mouginis-Mark, Jason Perry, William D. Smythe, Rosaly M. C. Lopes, L. W. Kamp, David A. Williams, Jani Radebaugh, Sylvain Douté, Robert W. Carlson, Elizabeth P. Turtle, and Jeffrey S. Kargel

Subjects
geography, geography.geographical_feature_category, biology, Lava, Astronomy and Astrophysics, Patera, Classification scheme, Thermal emission, biology.organism_classification, Plume, Astrobiology, symbols.namesake, Volcano, Space and Planetary Science, Galileo (satellite navigation), symbols, Geology
Abstract

Galileo's Near-Infrared Mapping Spectrometer (NIMS) obtained its final observations of Io during the spacecraft's fly-bys in August (I31) and October 2001 (I32). We present a summary of the observations and results from these last two fly-bys, focusing on the distribution of thermal emission from Io's many volcanic regions that give insights into the eruption styles of individual hot spots. We include a compilation of hot spot data obtained from Galileo, Voyager, and ground-based observations. At least 152 active volcanic centers are now known on Io, 104 of which were discovered or confirmed by Galileo observations, including 23 from the I31 and I32 Io fly-by observations presented here. We modify the classification scheme of Keszthelyi et al. (2001, J. Geophys. Res. 106 (E12) 33 025–33 052) of Io eruption styles to include three primary types: promethean (lava flow fields emplaced as compound pahoehoe flows with small plumes 200 km high plumes and rapidly-emplaced flow fields), and a new style we call “lokian” that includes all eruptions confined within paterae with or without associated plume eruptions). Thermal maps of active paterae from NIMS data reveal hot edges that are characteristic of lava lakes. Comparisons with terrestrial analogs show that Io's lava lakes have thermal properties consistent with relatively inactive lava lakes. The majority of activity on Io, based on locations and longevity of hot spots, appears to be of this third type. This finding has implications for how Io is being resurfaced as our results imply that eruptions of lava are predominantly confined within paterae, thus making it unlikely that resurfacing is done primarily by extensive lava flows. Our conclusion is consistent with the findings of Geissler et al. (2004, Icarus, this issue) that plume eruptions and deposits, rather than the eruption of copious amounts of effusive lavas, are responsible for Io's high resurfacing rates. The origin and longevity of islands within ionian lava lakes remains enigmatic.

Published
2004

44. Modeling the SAR backscatter of linear dunes on Earth and Titan

Author

Dominique Bernard, Ralph D. Lorenz, P. Paillou, Jani Radebaugh, A. Le Gall, Tom G. Farr, SSE 2014, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-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), Department of Geological Sciences [BYU], Brigham Young University (BYU), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), 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), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)

Subjects
Synthetic aperture radar, Scattering, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy and Astrophysics, Shuttle Radar Topography Mission, Physical optics, Space-based radar, law.invention, Physics::Geophysics, Condensed Matter::Soft Condensed Matter, symbols.namesake, 13. Climate action, Space and Planetary Science, law, Physics::Space Physics, Surface roughness, symbols, Astrophysics::Earth and Planetary Astrophysics, Radar, Titan (rocket family), Geology, Physics::Atmospheric and Oceanic Physics, Remote sensing
Abstract

International audience; We modeled the Synthetic Aperture Radar (SAR) response of linear dunes of the Great Sand Sea in Egypt using a single surface scattering term, based on Integral Equation and Physical Optics Models. Using multi-frequency SIR-C/X-SAR radar scenes and topography obtained from the Shuttle Radar Topography Mission (SRTM), we were able to estimate reasonable values for the parameters describing the surface roughness of the dunes. As the linear dunes of the Great Sand Sea are relevant analogs for the linear dunes observed on Titan by the Cassini Radar instrument, these results were thus used as a starting point to simulate the radar response of Titan's dunes, as imaged by the Radar instrument onboard the Cassini spacecraft during the T8 flyby in October 2005. We show that a single surface scattering term is not sufficient to simulate the radar signal backscattered by the dunes on Titan: one has to add a diffuse scattering term, indicating that Titan's dunes are likely to have somewhat inhomogeneous internal structures related to porosity and/or internal layering. Our results also indicate that the dunes on Titan should be close to perfectly smooth, possibly because of the formation of smaller ripples than on Earth, plus smoothing resulting from precipitation events.

Published
2014

45. Transient features in a Titan sea

Author

Howard A. Zebker, Philippe Paillou, Ralph D. Lorenz, Robert H. Brown, Christophe Sotin, Jason W. Barnes, Rosaly M. C. Lopes, Jason D. Hofgartner, Jani Radebaugh, S. D. Wall, Jonathan I. Lunine, P. D. Nicholson, Elizabeth P. Turtle, Pierre Encrenaz, Kevin H. Baines, Alexander G. Hayes, Bonnie J. Buratti, R. D. Kirk, Bryan Stiles, Michael Malaska, A. Le Gall, Charles A. Wood, Roger N. Clark, Karl L. Mitchell, Department of Astronomy [Ithaca], Cornell University [New York], Department of Electrical Engineering [Stanford], Stanford University, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), University of Idaho [Moscow, USA], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, US Geological Survey [Denver], United States Geological Survey [Reston] (USGS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), 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 de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Astrogeology Science Center [Flagstaff], 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), SSE 2014, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-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), Department of Geological Sciences [BYU], Brigham Young University (BYU), Planetary Science Institute [Tucson] (PSI), École normale supérieure - Paris (ENS-PSL), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)

Subjects
010504 meteorology & atmospheric sciences, Spacecraft, business.industry, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Ephemeral key, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, Astrobiology, Condensed Matter::Materials Science, symbols.namesake, 13. Climate action, Physics::Space Physics, 0103 physical sciences, symbols, General Earth and Planetary Sciences, Solstice, Astrophysics::Earth and Planetary Astrophysics, business, Titan (rocket family), 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

International audience; Titan's surface-atmosphere system bears remarkable similarities to Earth's, the most striking being an active, global methane cycle akin to Earth's water cycle1, 2. Like the hydrological cycle of Earth, Titan's seasonal methane cycle is driven by changes in the distribution of solar energy2. The Cassini spacecraft, which arrived at Saturn in 2004 in the midst of northern winter and southern summer, has observed surface changes, including shoreline recession, at Titan's south pole3, 4 and equator5. However, active surface processes have yet to be confirmed in the lakes and seas in Titan's north polar region6, 7, 8. As the 2017 northern summer solstice approaches, the onset of dynamic phenomena in this region is expected6, 7, 9, 10, 11, 12. Here we present the discovery of bright features in recent Cassini RADAR data that appeared in Titan's northern sea, Ligeia Mare, in July 2013 and disappeared in subsequent observations. We suggest that these bright features are best explained by the occurrence of ephemeral phenomena such as surface waves, rising bubbles, and suspended or floating solids. We suggest that our observations are an initial glimpse of dynamic processes that are commencing in the northern lakes and seas as summer nears in the northern hemisphere.

Published
2014

46. Global mapping and characterization of Titan's dune fields with Cassini: correlation between RADAR and VIMS observations

Author

Elizabeth P. Turtle, Jason W. Barnes, Olivier Bourgeois, S. Le Mouélic, Thomas Cornet, Antoine Lucas, T. Appéré, Robert H. Brown, L. Le Corre, E. Reffet, Christophe Sotin, Ralf Jaumann, Ralph D. Lorenz, Jani Radebaugh, Clément Narteau, Sebastien Rodriguez, Katrin Stephan, A. Le Gall, K. Arnold, S. Courrech du Pont, A. Garcia, Centre d'Etude de Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), 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), Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), 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), Planetary Science Institute [Tucson] (PSI), 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), Matière et Systèmes Complexes (MSC (UMR_7057)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Institut de Physique du Globe de Paris (IPGP), 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), Department of Geological Sciences [BYU], Brigham Young University (BYU), University of Idaho [Moscow, USA], DLR Institute of Planetary Research, German Aerospace Center (DLR), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Centre National d'Etudes Spatiales (CNES), Institut National des Sciences de l’Univers (INSU Programme National de Planétologie, France), Agence Natio- nale de la Recherche (ANR), UnivEarthS Labex program at Sorbonne Paris Cité, ANR-11-BS56-0002,APOSTIC,Analyse des Observations Photométriques pour l'Etude du Climat deTItan(2011), ANR-11-IDEX-0005,USPC,Université Sorbonne Paris Cité(2011), ANR-12-BS05-0001,EXO-DUNES,Caractérisation des environnements EXtra-terrestres de Mars et Titan par l'Observation et la modélisation des champs de DUNES(2012), 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 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), Matière et Systèmes Complexes (MSC), 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 de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Department of Physics [Moscow,USA], IMPEC - LATMOS, 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), and ANR-11-IDEX-0005-02/10-LABX-0023,UnivEarthS,Earth - Planets - Universe: observation, modeling, transfer(2011)

Subjects
Infrared observations, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy and Astrophysics, law.invention, Radar observations, Planetengeologie, Surface, symbols.namesake, 13. Climate action, Space and Planetary Science, law, symbols, Geological processes, Radar, Titan (rocket family), Titan, Geology, Remote sensing
Abstract

Vast fields of linear dunes have been observed in the equatorial regions of Titan, Saturn’s largest moon. As the Cassini mission, in orbit around Saturn since July 2004 and extended until May 2017, carries on, the high-resolution coverage of Titan’s surface increases, revealing new dune fields and allowing refinements in the examination of their properties. In this paper, we present the joint analysis of Cassini’s microwave and infrared global scale observations of Titan. Integrating within an up-to-date global map of Titan all the Cassini {RADAR} and {VIMS} (Visual and Infrared Mapping Spectrometer) images – the latter being empirically corrected for atmospheric scattering and surface photometry, from July 2004 through July 2013 and June 2010 respectively, we found very good qualitative and quantitative spatial matching between the geographic distribution of the dune fields and a specific infrared spectral unit (namely the “dark brown” unit). The high degree of spatial correlation between dunes and the “dark brown” unit has important implications for Titan’s geology and climate. We found that RADAR-mapped dunes and the “dark brown” unit are similarly confined within the equatorial belt (±30° in latitudes) with an equivalent distribution with latitude, suggesting an increasing sediment availability and mobility at Titan’s tropics relative to higher latitudes, compatible with the lower ground humidity predicted in equatorial regions by General Circulation Models. Furthermore, the strong correlation between RADAR-mapped dunes and the {VIMS} “dark brown” unit (72) allows us to better constrain the total surface area covered by dune material, previously estimated from the extrapolation of the {RADAR} observations alone. According to our calculations, dune material cover 17.5 ± 1.5 of Titan’s surface area, equivalent to a total surface area of 14.6 ± 1.2 million km2 (∼1.5 times the surface area of Earth’s Sahara desert). The {VIMS} “dark brown” coloration of the dune material is here confirmed at large spatial scale. If the sand particle composition is dominated by solid organics produced in and settling from the atmosphere, as supported by our spectral modeling and by previous spectral analysis, microwave radiometric data and atmospheric modeling, dune fields are one of the major surface hydrocarbon reservoirs on Titan. Assuming two possible scenarios for the sand distribution (either the sand is (1) entirely trapped in dune landforms, or (2) trapped in dunes at places where dune landforms are firmly observed and in sand sheets elsewhere), we estimate the volume of hydrocarbons trapped in the dune sediment to be comprised between 1.7 and 4.4 × 105 km3, corresponding to an average total mass of 230,000 GT, in comparison with ∼4000–30,000 GT of hydrocarbons in the polar lakes and seas. This indicates a maximum age for the dune sediments of ∼730-Myr, consistent with estimations of the ages of the current Titan’s atmospheric methane and surface.

Published
2014

47. Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission

Author

H. Herbert Breneman, M. P. Milazzo, Cynthia B. Phillips, Elizabeth P. Turtle, Alfred S. McEwen, Tilmann Denk, Damon P. Simonelli, Paul Geissler, Jani Radebaugh, Greg Levanas, David A. Williams, Laszlo P. Keszthelyi, and Kenneth P. Klaasen

Subjects
Atmospheric Science, Soil Science, Pyroclastic rock, Patera, Aquatic Science, Oceanography, Astrobiology, Jupiter, symbols.namesake, RED MATERIAL, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Galileo (satellite navigation), Earth-Surface Processes, Water Science and Technology, geography, geography.geographical_feature_category, Ecology, biology, Paleontology, Forestry, biology.organism_classification, Flow field, Galileo spacecraft, Geophysics, Volcano, Space and Planetary Science, symbols, Geology
Abstract

The Solid-State Imaging (SSI) instrument provided the first high- and medium-resolution views of Io as the Galileo spacecraft closed in on the volcanic body in late 1999 and early 2000. While each volcanic center has many unique features, the majority can be placed into one of two broad categories. The "Promethean" eruptions, typified by the volcanic center Prometheus, are characterized by long-lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years of decades. In contrast, "Pillanian" eruptions are characterized by large pyroclastic deposits and short-lived but high effusion rate eruptions from fissures feeding open-channel or open-sheet flows. Both types of eruptions commonly have ~100-km-tall, bright, SO2-rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas.

Published
2001

48. Mountains on Io: High-resolution Galileo observations, initial interpretations, and formation models

Author

Cynthia B. Phillips, Damon P. Simonelli, Laszlo P. Keszthelyi, M. P. Milazzo, Peter Schuster, Windy L. Jaeger, Alfred S. McEwen, Elizabeth P. Turtle, Jani Radebaugh, Frank C. Chuang, and Jeffrey M. Moore

Subjects
Atmospheric Science, Soil Science, Aquatic Science, Oceanography, Fault scarp, Mantle (geology), symbols.namesake, Geochemistry and Petrology, Lithosphere, Earth and Planetary Sciences (miscellaneous), Compression (geology), Earth-Surface Processes, Water Science and Technology, Ecology, Paleontology, Forestry, Subsidence, Crust, Geophysics, Galilean moons, Mountain formation, Space and Planetary Science, symbols, Geology, Seismology
Abstract

During three close flybys in late 1999 and early 2000 the Galileo spacecraft acquired new observations of the mountains that tower above Io's surface. These images have revealed surprising variety in the mountains' morphologies. They range from jagged peaks several kilometers high to lower, rounded structures. Some are very smooth, others are covered by numerous parallel ridges. Many mountains have margins that are collapsing outward in large landslides or series of slump blocks, but a few have steep, scalloped scarps. From these observations we can gain insight into the structure and material properties of Io's crust as well as into the erosional processes acting on Io. We have also investigated formation mechanisms proposed for these structures using finite-element analysis. Mountain formation might be initiated by global compression due to the high rate of global subsidence associated with Io's high resurfacing rate; however, our models demonstrate that this hypothesis lacks a mechanism for isolating the mountains. The large fraction (∼40%) of mountains that are associated with paterae suggests that in some cases these features are tectonically related. Therefore we have also simulated the stresses induced in Io's crust by a combination of a thermal upwelling in the mantle with global lithospheric compression and have shown that this can focus compressional stresses. If this mechanism is responsible for some of Io's mountains, it could also explain the common association of mountains with paterae.

Published
2001

49. Sand Seas of the Solar System

Author

Jani Radebaugh

Subjects
Solar System, symbols.namesake, Oceanography, biology, symbols, Venus, Mars Exploration Program, biology.organism_classification, Titan (rocket family), Geomorphology, Geology
Abstract

Jani Radebaugh of Brigham Young University journeys to a different kind of ocean: seas of sand. Dune-covered deserts have an ocean-like quality. The sheer volume of constantly moving material, the challenge to navigation and survival, and the regular undulations of sand akin to waves on water in oceans led explorers and scientists to term these regions on Earth “sand seas”. Radebaugh provides an overview of the bizarre dune seas on Venus, Earth, Mars and Titan.

Published
2013

50. AVIATR - Aerial Vehicle for In-Situ and Airborne Titan Reconnaissance : A Titan Airplane Mission Concept

Author

Francesco Giannini, E. L. Schaller, K. Reh, Ross A. Beyer, Christopher P. McKay, Jani Radebaugh, F. Michael Flasar, Carrie M. Anderson, Jon Merrison, Sebastien Rodriguez, Rick Foch, Jonathan L. Mitchell, Lawrence G. Lemke, Terry Hurford, Máté Ádámkovics, Sean Bain, Jason W. Barnes, Stéphane Le Mouélic, Kunio M. Sayanagi, Angioletta Coradini, Jay Gundlach, A. James Friedson, Kenneth S. Edgett, David H. Atkinson, Ralph D. Lorenz, David D. Morabito, Simon A. Kattenhorn, Devon M. Burr, Michael J. Malaska, Anthony Colaprete, Alberto Adriani, 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
business.product_category, 010504 meteorology & atmospheric sciences, Cruise, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, 7. Clean energy, Airplane, law.invention, symbols.namesake, law, 0103 physical sciences, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Remote sensing, Spacecraft, business.industry, Astronomy and Astrophysics, 13. Climate action, Space and Planetary Science, Radar altimeter, Gravity assist, symbols, Aerial reconnaissance, business, Space vehicle, Titan (rocket family)
Abstract

We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14 km altitude and descend down to 3.5 km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini's discoveries and can likely do so within a New Frontiers budget.

Published
2011

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