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353 results on '"Dale P. Cruikshank"'

1. Revealing Callisto’s Carbon-rich Surface and CO2 Atmosphere with JWST

Author

Richard J. Cartwright, Geronimo L. Villanueva, Bryan J. Holler, Maria Camarca, Sara Faggi, Marc Neveu, Lorenz Roth, Ujjwal Raut, Christopher R. Glein, Julie C. Castillo-Rogez, Michael J. Malaska, Dominique Bockelée-Morvan, Tom A. Nordheim, Kevin P. Hand, Giovanni Strazzulla, Yvonne J. Pendleton, Katherine de Kleer, Chloe B. Beddingfield, Imke de Pater, Dale P. Cruikshank, and Silvia Protopapa

Subjects
Infrared spectroscopy, Galilean satellites, Callisto, James Webb Space Telescope, Natural satellite atmospheres, Natural satellite surfaces, Astronomy, QB1-991
Abstract

We analyzed spectral cubes of Callisto’s leading and trailing hemispheres, collected with the NIRSpec Integrated Field Unit (G395H) on the James Webb Space Telescope. These spatially resolved data show strong 4.25 μ m absorption bands resulting from solid-state ^12 CO _2 , with the strongest spectral features at low latitudes near the center of its trailing hemisphere, consistent with radiolytic production spurred by magnetospheric plasma interacting with native H _2 O mixed with carbonaceous compounds. We detected CO _2 rovibrational emission lines between 4.2 and 4.3 μ m over both hemispheres, confirming the global presence of CO _2 gas in Callisto’s tenuous atmosphere. These results represent the first detection of CO _2 gas over Callisto’s trailing side. The distribution of CO _2 gas is offset from the subsolar region on either hemisphere, suggesting that sputtering, radiolysis, and geologic processes help sustain Callisto’s atmosphere. We detected a 4.38 μ m absorption band that likely results from solid-state ^13 CO _2 . A prominent 4.57 μ m absorption band that might result from CN-bearing organics is present and significantly stronger on Callisto’s leading hemisphere, unlike ^12 CO _2 , suggesting these two spectral features are spatially antiassociated. The distribution of the 4.57 μ m band is more consistent with a native origin and/or accumulation of dust from Jupiter’s irregular satellites. Other, more subtle absorption features could result from CH-bearing organics, CO, carbonyl sulfide, and Na-bearing minerals. These results highlight the need for preparatory laboratory work and improved surface–atmosphere interaction models to better understand carbon chemistry on the icy Galilean moons before the arrival of NASA’s Europa Clipper and ESA’s JUICE spacecraft.

Published
2024
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2. Large-scale cryovolcanic resurfacing on Pluto

Author

Kelsi N. Singer, Oliver L. White, Bernard Schmitt, Erika L. Rader, Silvia Protopapa, William M. Grundy, Dale P. Cruikshank, Tanguy Bertrand, Paul M. Schenk, William B. McKinnon, S. Alan Stern, Rajani D. Dhingra, Kirby D. Runyon, Ross A. Beyer, Veronica J. Bray, Cristina Dalle Ore, John R. Spencer, Jeffrey M. Moore, Francis Nimmo, James T. Keane, Leslie A. Young, Catherine B. Olkin, Tod R. Lauer, Harold A. Weaver, and Kimberly Ennico-Smith

Subjects
Science
Abstract

Giant icy volcanos (cryovolcanos) on Pluto are unique in the imaged solar system and provide evidence for unexpected, active geology late in Pluto’s history.

Published
2022
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3. A CO2 Cycle on Ariel? Radiolytic Production and Migration to Low-latitude Cold Traps

Author

Richard J. Cartwright, Tom A. Nordheim, Riley A. DeColibus, William M. Grundy, Bryan J. Holler, Chloe B. Beddingfield, Michael M. Sori, Michael P. Lucas, Catherine M. Elder, Leonardo H. Regoli, Dale P. Cruikshank, Joshua P. Emery, Erin J. Leonard, and Corey J. Cochrane

Subjects
Uranian satellites, Planetary surfaces, Surface composition, Surface processes, Surface ices, Astronomy, QB1-991
Abstract

CO _2 ice is present on the trailing hemisphere of Ariel but is mostly absent from its leading hemisphere. The leading/trailing hemispherical asymmetry in the distribution of CO _2 ice is consistent with radiolytic production of CO _2 , formed by charged particle bombardment of H _2 O ice and carbonaceous material in Ariel’s regolith. This longitudinal distribution of CO _2 on Ariel was previously characterized using 13 near-infrared reflectance spectra collected at “low” sub-observer latitudes between 30°S and 30°N. Here we investigated the distribution of CO _2 ice on Ariel using 18 new spectra: 2 collected over low sub-observer latitudes, 5 collected at “mid” sub-observer latitudes (31°N–44°N), and 11 collected over “high” sub-observer latitudes (45°N–51°N). Analysis of these data indicates that CO _2 ice is primarily concentrated on Ariel’s trailing hemisphere. However, CO _2 ice band strengths are diminished in the spectra collected over mid and high sub-observer latitudes. This sub-observer latitudinal trend may result from radiolytic production of CO _2 molecules at high latitudes and subsequent migration of this constituent to low-latitude cold traps. We detected a subtle feature near 2.13 μ m in two spectra collected over high sub-observer latitudes, which might result from a “forbidden” transition mode of CO _2 ice that is substantially stronger in well-mixed substrates composed of CO _2 and H _2 O ice, consistent with regolith-mixed CO _2 ice grains formed by radiolysis. Additionally, we detected a 2.35 μ m feature in some low sub-observer latitude spectra, which might result from CO formed as part of a CO _2 radiolytic production cycle.

Published
2022
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4. Organic Components of Small Bodies in the Outer Solar System: Some Results of the New Horizons Mission

Author

Dale P. Cruikshank, Yvonne J. Pendleton, and William M. Grundy

Subjects
Solar System, Pluto, Charon, Arrokoth, Kuiper Belt object, complex organics, Science
Abstract

The close encounters of the Pluto–Charon system and the Kuiper Belt object Arrokoth (formerly 2014 MU69) by NASA’s New Horizons spacecraft in 2015 and 2019, respectively, have given new perspectives on the most distant planetary bodies yet explored. These bodies are key indicators of the composition, chemistry, and dynamics of the outer regions of the Solar System’s nascent environment. Pluto and Charon reveal characteristics of the largest Kuiper Belt objects formed in the dynamically evolving solar nebula inward of ~30 AU, while the much smaller Arrokoth is a largely undisturbed relic of accretion at ~45 AU. The surfaces of Pluto and Charon are covered with volatile and refractory ices and organic components, and have been shaped by geological activity. On Pluto, N2, CO and CH4 are exchanged between the atmosphere and surface as gaseous and condensed phases on diurnal, seasonal and longer timescales, while Charon’s surface is primarily inert H2O ice with an ammoniated component and a polar region colored with a macromolecular organic deposit. Arrokoth is revealed as a fused binary body in a relatively benign space environment where it originated and has remained for the age of the Solar System. Its surface is a mix of CH3OH ice, a red-orange pigment of presumed complex organic material, and possibly other undetected components.

Published
2020
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6. Geologic Landforms and Chronostratigraphic History of Charon as Revealed by a Hemispheric Geologic Map

Author

Stuart J. Robbins, Ross A. Beyer, John R. Spencer, William M. Grundy, Oliver L. White, Kelsi N. Singer, Jeffrey M. Moore, Cristina M. Dalle Ore, William B. McKinnon, Carey M. Lisse, Kirby Runyon, Chloe B. Beddingfield, Paul Schenk, Orkan M. Umurhan, Dale P. Cruikshank, Tod R. Lauer, Veronica J. Bray, Richard P. Binzel, Marc W. Buie, Bonnie J. Buratti, Andrew F. Cheng, Ivan R. Linscott, Dennis C. Reuter, Mark R. Showalter, Leslie A. Young, Catherine B. Olkin, Kimberly S. Ennico, Harold A. Weaver, and S. Alan Stern

Published
2019
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7. Dione’s Wispy Terrain: A Cryovolcanic Story?

Author

Cristina M Dalle Ore, Christopher J Long, Fiona Nichols-Fleming, Francesca Scipioni, Edgard G Rivera Valentín, Andy J Lopez Oquendo, and Dale P Cruikshank

Subjects
Astrophysics
Abstract

We examine the H2O ice phase on the surface of Dione, one of Saturn's icy satellites, to investigate whether it might harbor cryovolcanic activity induced by a subcrustal body of water. Several studies have searched for such a signature, as summarized in Buratti et al.; however, none has yet produced sufficient evidence to dissipate doubts. In the radiation environment characteristic of Saturn's icy moons, the presence of crystalline H2O ice has been used as a marker of a high-temperature region. Because ion bombardment will, over time, drive crystalline ice toward an increasingly amorphous state, the current phase of the H2O ice can be used to gauge the temporal temperature evolution of the surface. We adopt a technique described by Dalle Ore et al. to map the fraction of amorphous to crystalline H2O ice on Dione's surface, observed by the Cassini Visible and Infrared Mapping Spectrometer, and provide an ice exposure age. We focus on a region observed at high spatial resolution and centered on one of the faults of the Wispy Terrain, which is measured to be fully crystalline. By assuming an amorphous to crystalline ice fraction of 5% (i.e., 95% crystallinity), significantly higher than the actual measurement, we obtain an upper limit for the age of the fault of 152 Ma. This implies that the studied fault has been active in the last ~100 Ma, supporting the hypothesis that Dione might still be active or was active a very short time ago, and similarly to Enceladus, might still be harboring a body of liquid water under its crust.

Published
2021
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8. Stress-Activated Electric Currents in Icy Planetary Bodies: H2O2-Doped H2O Ices

Author

Friedemann T Freund, Jaufray Sornette, Corey Stockburger, Cary T. Keller, Amber Gray, and Dale P Cruikshank

Subjects
Astrophysics
Abstract

Planetary satellites such as the Jovian moon Europa and several Kuiper Belt objects (including Pluto) have surfaces consisting largely of H2O ice, which is brittle and behaves as a rock at the low temperatures that prevail in the outer Solar System. Several of those ice-crusted bodies show evidence of tectonic activity indicating high levels of stress. This paper reports on laboratory experiments with pure H2O ice and H2O2–doped H2O ices with H2O2 concentration levels comparable to those in the ices of Europa. Elongated rectangular ice blocks at T = −81 °C [192 K] were stressed at one end to test whether electric currents are generated and capable of flowing down the stress gradient. Pure H2O ice was found to not produce currents above the 10−10 A background level except for occasional transients in the 10−9–10−8 A range during fracture or rapid plastic deformation due to electrons, e’. By contrast, stressing H2O2-doped H2O ices consistently produced electric currents in the 10−7–10−5 A range, due to holes, h•, propagating from the stressed end to the unstressed end. The h• charge carriers are generated by the break-up of peroxy bonds of H2O2 molecules, leading to O−, equivalent to defect electrons or holes h• in the O2− matrix.

Published
2021
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9. Cryovolcanic flooding in Viking Terra on Pluto

Author

Dale P Cruikshank, Cristina M Dalle Ore, Francesca Scipioni, Ross A Beyer, Oliver L White, Jeffrey M Moore, William M Grundy, Bernard Schmitt, Kirby D. Runyon, James T Keane, Stuart J. Robbins, S Alan Stern, Tanguy Bertrand, Chloe B Beddingfield, Catherine B Olkin, Leslie A. Young, Harold A Weaver, and Kimberly Ennico

Subjects
Astrophysics
Abstract

A prominent fossa trough (Uncama Fossa) and adjacent 28-km diameter impact crater (Hardie) in Pluto's Viking Terra, as seen in the high-resolution images from the New Horizons spacecraft, show morphological evidence of in-filling with a material of uniform texture and red-brown color. A linear fissure parallel to the trough may be the source of a fountaining event yielding a cryoclastic deposit having the same composition and color properties as is found in the trough and crater. Spectral maps of this region with the New Horizons LEISA instrument reveal the spectral signature of H2O ice in these structures and in distributed patches in the adjacent terrain in Viking Terra. A detailed statistical analysis of the spectral maps shows that the colored H2O ice filling material also carries the 2.2-μm signature of an ammoniated component that may be an ammonia hydrate (NH3·nH2O) or an ammoniated salt. This paper advances the view that the crater and fossa trough have been flooded by a cryolava debouched from Pluto's interior along fault lines in the trough and in the floor of the impact crater. The now frozen cryolava consisted of liquid H2O infused with the red-brown pigment presumed to be a tholin, and one or more ammoniated compounds. Although the abundances of the pigment and ammoniated compounds entrained in, or possibly covering, the H2O ice are unknown, the strong spectral bands of the H2O ice are clearly visible. In consideration of the factors in Pluto's space environment that are known to destroy ammonia and ammonia-water mixtures, the age of the exposure is of order ≤109 years. Ammoniated salts may be more robust, and laboratory investigations of these compounds are needed.

Published
2021
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10. Determination of the Complex Refractive Indices of Aerosol Analogs Formed at Low Temperatures with the NASA Ames Optical Constants Facility (OCF)

Author

Ella M Sciamma-O'Brien, Ted L Roush, Farid Salama, Tanguy Bertrand, Jason Campbell Cook, Dale P Cruikshank, Cristina Dalle Ore, and William M Grundy

Subjects
Ground Support Systems And Facilities (Space)
Abstract

The NASA Ames COsmic SImulation Chamber (COSmIC) [1] is a unique experimental facility that allows: 1) cooling a gas mixture to low temperature (150 K) in a jet expansion before inducing chemistry by plasma; and 2) controlling the extent of the chemical reactions by employing a pulsed plasma discharge. This enables the study of the early stages of aerosol production, as well as specific chemical pathways in planetary environments (e.g. Titan’s and Pluto’s atmospheres). Both the gas and solid products can be studied. For a decade COSmIC has been used to simulate Titan’s atmospheric chemistry at low, Titan-like temperature [2]. New developments on the COSmIC facility are investigating formation of aerosols in tenuous, or transitory, atmospheres of other icy bodies [3-5], as well as cool exoplanets atmospheres having a hydrocarbon component, that results in formation of hazes and/or surface deposits of refractory materials. The new Ames Optical Constants Facility enables determination of the aerosol analogs' complex refractive indices, n and k, from 0.59 to 200 μm [2]. Here we report efforts of determining n and k from ex-situ transmission measurements of solid samples produced from binary N-CH and Ar-CH, and tertiary N-CH-CH and Ar-CH-CHgas mixtures in COSmIC, and deposited onto various substrates. A computational technique [6] that addresses interference fringes observed in the laboratory transmission data, particularly at wavelengths < 3 μm, has been implemented and applied to determine n and k for the samples. At visible and near-infrared wavelengths(0.4-1.6 μm) the deposit thickness, and its variation, as well as n and k were determined by a commercial entity. These data provide the ability to compare results, from independent methods, in the region of overlap between the two approaches.

Published
2020

11. Evidence for Ammonia-bearing Species on the Uranian Satellite Ariel Supports Recent Geologic Activity

Author

Richard J. Cartwright, Chloe B. Beddingfield, Tom A. Nordheim, Joseph Roser, William M. Grundy, Kevin P. Hand, Joshua P. Emery, Dale P Cruikshank, and Francesca Scipioni

Subjects
Geosciences (General)
Abstract

We investigated whether ammonia-rich constituents are present on the surface of the Uranian moon Ariel by analyzing 32 near-infrared reflectance spectra collected over a wide range of sub-observer longitudes and latitudes. We measured the band areas and depths of a 2.2 μm feature in these spectra, which has been attributed to ammonia-bearing species on other icy bodies. Ten spectra display prominent 2.2 μm features with band areas and depths >2σ. We determined the longitudinal distribution of the 2.2 μm band, finding no statistically meaningful differences between Ariel’s leading and trailing hemispheres, indicating that this band is distributed across Ariel’s surface. We compared the band centers and shapes of the five Ariel spectra displaying the strongest 2.2 μm bands to laboratory spectra of various ammonia-bearing and ammonium-bearing species, finding that the spectral signatures of the Ariel spectra are best matched by ammonia-hydrates and flash frozen ammonia-water solutions. Our analysis also revealed that four Ariel spectra display 2.24 μm bands (>2σ band areas and depths), with band centers and shapes that are best matched by ammonia ice. Because ammonia should be efficiently removed over short timescales by ultraviolet photons, cosmic rays, and charged particles trapped in Uranus’ magnetosphere, the possible presence of this constituent supports geologic activity in the recent past, such as emplacement of ammonia-rich cryolavas and exposure of ammonia-rich deposits by tectonism, impact events, and mass wasting.

Published
2020
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12. Disk-resolved Photometric Properties of Pluto and the Coloring Materials across its Surface

Author

Silvia Protopapa, Cathy B. Olkin, Will M. Grundy, Jian-Yang Li, Anne Verbiscer, Dale P. Cruikshank, Thomas Gautier, Eric Quirico, Jason C. Cook, Dennis Reuter, Carly J. A. Howett, Alan Stern, Ross A. Beyer, Simon Porter, Leslie A. Young, Harold A. Weaver, Kimberly Ennico, Cristina M. Dalle Ore, Francesca Scipioni, and Kelsi N. Singer

Subjects
Astronomy, Astrophysics
Abstract

A multiwavelength regionally dependent photometric analysis of Pluto's anti-Charon-facing hemisphere using images collected by New Horizons' Multispectral Visible Imaging Camera (MVIC) reveals large variations in the absolute value and spectral slope of the single-scattering albedo. Four regions of interest are analyzed: the dark equatorial belt, Pluto's north pole, nitrogen-rich regions, and the mid-latitude terrains. Regions dominated by volatile ices such as Lowell Regio and Sputnik Planitia present single-scattering albedos of ~0.98 at 492 nm, almost neutral across MVIC's visible wavelength range (400–910 nm), indicating limited contributions from tholin materials. Pluto's dark equatorial regions, informally named Cthulhu and Krun Maculae, have single-scattering albedos of ~0.16 at 492 nm and are the reddest regions. Applying the Hapke radiative transfer model to combined MVIC and Linear Etalon Imaging Spectral Array (LEISA) spectra (400–2500 nm) of Cthulhu Macula and Lowell Regio successfully reproduces the spectral properties of these two regions of dramatically disparate coloration, composition, and morphology. Since this model uses only a single coloring agent, very similar to the Titan-like tholin of Khare et al., to account for all of Pluto's colors, this result supports the Grundy et al. conclusion that Pluto's coloration is the result of photochemical products mostly produced in the atmosphere. Although cosmic rays and extreme ultraviolet photons reach Pluto's surface where they can drive chemical processing, observations of diverse surface colors do not require different chemical products produced in different environments. We report a correction scaling factor in the LEISA radiometric calibration of 0.74 ± 0.05.

Published
2020
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13. Great Expectations: Plans and Predictions for New Horizons Encounter With Kuiper Belt Object 2014 MU69 (“Ultima Thule')

Author

Jeffrey M. Moore, William B. McKinnon, Dale P. Cruikshank, G. Randall Gladstone, John R. Spencer, S. Alan Stern, Harold A. Weaver, Kelsi N. Singer, Mark R. Showalter, William M. Grundy, Ross A. Beyer, Oliver L. White, Richard P. Binzel, Marc W. Buie, Bonnie J. Buratti, Andrew F. Cheng, Carly Howett, Cathy B. Olkin, Alex H. Parker, Simon B. Porter, Paul M. Schenk, Henry B. Throop, Anne J. Verbiscer, Leslie A. Young, Susan D. Benecchi, Veronica J. Bray, Carrie L. Chavez, Rajani D. Dhingra, Alan D. Howard, Tod R. Lauer, C. M. Lisse, Stuart J. Robbins, Kirby D. Runyon, and Orkan M. Umurhan

Published
2018
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16. On a radiolytic origin of red organics at the surface of the Arrokoth Trans-Neptunian Object

Author

Eric Quirico, Aurore Bacmann, Cédric Wolters, Basile Augé, Laurène Flandinet, Thibault Launois, John F. Cooper, Véronique Vuitton, Thomas Gautier, Lora Jovanovic, Philippe Boduch, Hermann Rothard, Léopold Desage, Alexandre Faure, Bernard Schmitt, Olivier Poch, William M. Grundy, Silvia Protopapa, Sonia Fornasier, Dale P. Cruikshank, S. Alan Stern, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, NASA Goddard Space Flight Center (GSFC), PLANETO - 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Lowell Observatory [Flagstaff], Southwest Research Institute [Boulder] (SwRI), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), and University of Central Florida [Orlando] (UCF)

Subjects
[SDU]Sciences of the Universe [physics], Space and Planetary Science, Astronomy and Astrophysics
Abstract

International audience; The classical Kuiper Belt Object (KBO) Arrokoth was surveyed by the New Horizons spacecraft on 1st January 2019, revealing a small bilobed object with a red surface, whose spectral slope lies in the average of the whole KBOs population. This red color has been assigned to reddish organic materials, either inherited from the protosolar disk during accretion, or formed through radiolytic processes in the surface due to exposure to solar or interstellar photons, Solar Wind, Solar Energetic Particles or Galactic Cosmic Rays. We report here a study investigating the radiolytic scenario, based on numerical calculations and experimental simulations run with swift heavy ions (74.8 MeV136Xe19+ and 33.06 MeV58Ni9+), and low-energy 105 keV18O6+ions on CH3OH ice, the only molecule identified at Arrokoth’s surface.

Published
2023
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17. Spitzer’s Solar System studies of comets, centaurs and Kuiper belt objects

Author

James Bauer, David E. Harker, Diane H. Wooden, Yanga R. Fernandez, Noemi Pinilla-Alonso, William T. Reach, Dale P. Cruikshank, Adam J. McKay, Josh Emery, David Trilling, Robert D. Gehrz, John Stansberry, Carey M. Lisse, Charles E. Woodward, Yvonne J. Pendleton, Michael S. P. Kelley, Mark V. Sykes, and Estela Fernández-Valenzuela

Subjects
Planetesimal, Solar System, 010504 meteorology & atmospheric sciences, Infrared, James Webb Space Telescope, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Centaur, 01 natural sciences, Spitzer Space Telescope, Planet, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Formation and evolution of the Solar System, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

In its 16 years of scientific measurements, the Spitzer Space Telescope performed ground-breaking and key infrared measurements of Solar System objects near and far. Targets ranged from the smallest planetesimals to the giant planets; Spitzer helped us to reshape our understanding of these objects while also laying the groundwork for future infrared space-based observations like those to be undertaken by the James Webb Space Telescope in the 2020s. In this Review Article, we describe how Spitzer advanced our knowledge of Solar System formation and evolution through observations of small outer Solar System planetesimals—that is, comets, centaurs and Kuiper belt objects (KBOs). Relics from the early formation era of our Solar System, these objects hold important information about the processes that created them.We group Spitzer’s key contributions into three broad classes: characterization of new Solar System objects (comets D/ISON 2012 S1, C/2016 R2 and 1I/‘Oumuamua); large population surveys of known objects (comets, centaurs and KBOs); and compositional studies through spectral measurements of body surfaces and emitted materials. In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this first Review Article of a pair, Spitzer’s insights into comets, centaurs and Kuiper belt objects—all remnants of the Solar System’s formation—are summarized.

Published
2020
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20. Volatile transport modeling on Triton with new observational constraints

Author

M. Vangvichith, Emmanuel Lellouch, F. Merlin, Oliver L. White, Bruno Sicardy, Eric Quirico, J. Marques Oliveira, Leslie A. Young, Dale P. Cruikshank, Tanguy Bertrand, John Stansberry, Ehouarn Millour, Candice Hansen, David Dubois, Bryan J. Holler, Paul M. Schenk, François Forget, Apurva Oza, Bernard Schmitt, William M. Grundy, and Jeffrey M. Moore

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Flux, Astronomy and Astrophysics, Context (language use), Albedo, Surface pressure, Atmospheric sciences, Latitude, Pluto, Space and Planetary Science, Neptune, Internal heating, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

Neptune's moon Triton shares many similarities with Pluto, including volatile cycles of N2, CH4 and CO, and represents a benchmark case for the study of surface-atmosphere interactions on volatile-rich KBOs. Within the context of New Horizons observations of Pluto as well as recent Earth-based observations of Triton, we adapt a Plutonian VTM to Triton, and test its ability to simulate its volatile cycles, thereby aiding our understanding of its climate. We present VTM simulations exploring the volatile cycles on Triton over long-term and seasonal timescales for varying model parameters. We explore what scenarios and model parameters allow for a best match of the available observations. In particular, our set of observational constraints include Voyager 2 observations, ground-based NIR (0.8 to 2.4 ��m) disk-integrated spectra and the evolution of surface pressure as retrieved from stellar occultations. Our results show that Triton's poles act as cold traps for volatile ices and favor the formation of polar caps extending to lower latitudes through glacial flow. As previously evidenced by other VTMs, North-South asymmetries in surface properties can favor the development of one cap over the other. Our best-case simulations are obtained for a global reservoir of N2 ice thicker than 200 m and a bedrock thermal inertia larger than 500 SI. The large N2 ice reservoir implies a permanent N2 southern cap extending to the equator. Our results also suggest that a small permanent polar cap exists in the northern (currently winter) hemisphere if the internal heat flux remains radiogenic (< 3 mW m-2). Finally, we provide predictions for the evolution of ice distribution, surface pressure, CO and CH4 atmospheric mixing ratios in the next decades. We also model the thermal lightcurves of Triton in 2022, which serve as predictions for future JWST observations., 69 pages, 29 figures, 3 tables. Accepted for publication in Icarus

Published
2021

21. Triton: Topography and Geology of a Probable Ocean World with Comparison to Pluto and Charon

Author

Carver J. Bierson, John R. Spencer, Jason D. Hofgartner, Dale P. Cruikshank, Tanguy Bertrand, Emily S. Martin, S. A. Stern, Ross A. Beyer, T. Stryk, Stuart J. Robbins, Kelsi N. Singer, Kirby Runyon, Candice Hansen, William M. Grundy, William B. McKinnon, Chloe B. Beddingfield, Jeffrey M. Moore, Veronica J. Bray, and Paul M. Schenk

Subjects
Convection, geography, geography.geographical_feature_category, Pluto, Science, Dwarf planet, ocean world, Massif, Icy moon, Plume, Astrobiology, Volcano, topography, Neptune, Triton, General Earth and Planetary Sciences, cartography, Geology
Abstract

The topography of Neptune’s large icy moon Triton could reveal important clues to its internal evolution, but has been difficult to determine. New global digital color maps for Triton have been produced as well as topographic data for

Published
2021
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22. Isotopic ratios of Saturn's rings and satellites: Implications for the origin of water and Phoebe

Author

Robert H. Brown, Dale P. Cruikshank, Gregg A. Swayze, and Roger N. Clark

Subjects
Physics, Solar System, Vienna Standard Mean Ocean Water, 010504 meteorology & atmospheric sciences, Origin of water on Earth, Rings of Saturn, Astronomy and Astrophysics, Tholin, Astrophysics, 01 natural sciences, Interstellar medium, Space and Planetary Science, Saturn, 0103 physical sciences, Radiative transfer, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

Isotopic ratios have long been used to learn about physical processes acting over a wide range of geological environments, and in constraining the origin and/or evolution of planetary bodies. We report the spectroscopic detection of deuterium in Saturn's rings and satellites, and use these measurements to determine the (D/H) ratios in their near-surface regions. Saturn's moons, Phoebe and Iapetus, show a strong signature of CO2 and the 13C component of this molecule is detected and quantified. Large averages of spectra obtained by the Cassini Visual and Infrared Mapping Spectrometer, VIMS, were computed for the rings and icy satellites. The observed intensities of the infrared absorptions in H2O and CO2 and their isotopes were calibrated using laboratory data and radiative transfer models to derive the D/H and 13C/12C ratios. We find that the D/H in Saturn's rings and satellites is close to the Vienna Standard Mean Ocean Water (VSMOW) and bulk Earth (4% lower than VSMOW) value except for Phoebe, which is 8.3 times the VSMOW value. This is the highest value for any Solar-System surface yet measured, and suggests that Phoebe formed from material with a different D/H ratio than the other satellites in the Saturn system. Phoebe's 13C/12C ratio is also unusual: 4.7 times greater than terrestrial, and greater than values measured for the interstellar medium and the galactic center. The high 13C abundance in the CO2 suggests that Phoebe was never warm enough for the large D/H ratio in its surface to have originated by evaporative fractionation of its water ice (e.g., from heating in the inner Solar System before its eventual capture by Saturn). We also report the detection of a probable O-D stretch absorption due to OD in minerals on Phoebe at 3.62 μm. This absorption is not detected on other Saturnian satellites. Stronger signatures of bound water absorptions are found in the dark material of Iapetus and we report a new detection of bound water at 1.9 μm. The position of this absorption matches that seen in spectra of hydrated iron oxides but does not match absorptions seen in spectra of tholins. Despite the strong bound water signature in the Iapetus dark material, no 3.62 μm OD absorption is seen in the spectra, further indicating the high deuterium level on Phoebe is unusual. As such, it is likely that Phoebe originated in a colder part of the outer Solar System, relative to the prevailing temperatures at Saturn's distance from the Sun.

Published
2019
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23. Geologic Landforms and Chronostratigraphic History of Charon as Revealed by a Hemispheric Geologic Map

Author

William B. McKinnon, Veronica J. Bray, John R. Spencer, Bonnie J. Buratti, Richard P. Binzel, S. Alan Stern, Kirby Runyon, Jeffrey M. Moore, Ross A. Beyer, Dale P. Cruikshank, Paul M. Schenk, Orkan M. Umurhan, Catherine B. Olkin, Dennis C. Reuter, Kelsi N. Singer, Cristina M. Dalle Ore, Mark R. Showalter, Ivan Linscott, Stuart J. Robbins, Chloe B. Beddingfield, Oliver L. White, Tod R. Lauer, Marc W. Buie, Kimberly Ennico, Carey M. Lisse, Harold A. Weaver, William M. Grundy, Leslie A. Young, and Andrew F. Cheng

Subjects
Paleontology, Tectonics, geography, Geophysics, New horizons, geography.geographical_feature_category, Space and Planetary Science, Geochemistry and Petrology, Landform, Earth and Planetary Sciences (miscellaneous), Geologic map, Geology
Published
2019
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24. Pluto's Sputnik Planitia: Composition of geological units from infrared spectroscopy

Author

J. M. Moore, R. P. Binzel, Kelsi N. Singer, Harold A. Weaver, Bernard Schmitt, Francesca Scipioni, A. J. Verbiscer, Catherine B. Olkin, Tanguy Bertrand, Silvia Protopapa, D. C. Reuter, C. M. Dalle Ore, C. Beddingfield-Cartwright, Oliver L. White, D. E. Jennings, J. R. Spencer, Dale P. Cruikshank, Jason C. Cook, Leslie A. Young, William M. Grundy, S. A. Stern, Search for Extraterrestrial Intelligence Institute (SETI), NASA Ames Research Center (ARC), Pinhead Institute, Lowell Observatory [Flagstaff], Massachusetts Institute of Technology (MIT), NASA Goddard Space Flight Center (GSFC), Southwest Research Institute [Boulder] (SwRI), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), University of Virginia [Charlottesville], and CNES, système Solaire

Subjects
Endmember, 010504 meteorology & atmospheric sciences, Pluto, Near-infrared spectroscopy, Elevation, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mineralogy, surface composition, Astronomy and Astrophysics, Tholin, 15. Life on land, geological units, Spatial distribution, 01 natural sciences, Spectral line, ices, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Spectral slope, infrared spectroscopy, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

International audience; We have compared spectroscopic data of Sputnik Planitia on Pluto, as acquired by New Horizons’ Linear Etalon Imaging Spectral Array (LEISA) instrument, to the geomorphology as mapped by White et al. (2017) using visible and panchromatic imaging acquired by the LOng-Range Reconnaissance Imager (LORRI) and the Multi-spectral Visible Imaging Camera (MVIC). We have focused on 13 of the geologic units identified by White et al. (2017), which include the plains and mountain units contained within the Sputnik basin. We divided the map of Sputnik Planitia into 15 provinces, each containing one or more geologic units, and we use LEISA to calculate the average spectra of the units inside the 15 provinces. Hapke-based modeling was then applied to the average spectra of the units to infer their surface composition, and to determine if the composition resulting from the modeling of LEISA spectra reflects the geomorphologic analyses of LORRI data, and if areas classified as being the same geologically, but which are geographically separated, share a similar composition. We investigated the spatial distribution of the most abundant ices on Pluto’s surface - CH4, N2, CO, H2O, and a non-ice component presumed to be a macromolecular carbon-rich material, termed a tholin, that imparts a positive spectral slope in the visible spectral region and a negative spectral slope longward of ~1.1 μm. Because the exact nature of the non-ice component is still debated and because the negative spectral slope of the available tholins in the near infrared does not perfectly match the Pluto data, for spectral modeling purposes we reference it generically as the negative spectral slope endmember (NSS endmember). We created maps of variations in the integrated band depth (from LEISA data) and areal mass fraction (from the modeling) of the components. The analysis of correlations between the occurrences of the endmembers in the geologic units led to the observation of an anomalous suppression of the strong CH4 absorption bands in units with compositions that are dominated by H2O ice and the NSS endmember. Exploring the mutual variation of the CH4 and N2 integrated band depths with the abundance of crystalline H2O and NSS endmember revealed that the NSS endmember is primarily responsible for the suppression of CH4 absorptions in mountainous units located along the western edge of Sputnik Planitia. Our spectroscopic analyses have provided additional insight into the geological processes that have shaped Sputnik Planitia. A general increase in volatile abundance from the north to the south of Sputnik Planitia is observed. Such an increase first observed and interpreted by Protopapa et al., 2017 and later confirmed by climate modeling (Bertrand et al., 2018) is expressed geomorphologically in the form of preferential deposition of N2 ice in the upland and mountainous regions bordering the plains of southern Sputnik Planitia. Relatively high amounts of pure CH4 are seen at the southern Tenzing Montes, which are a natural site for CH4 deposition owing to their great elevation and the lower insolation they are presently receiving. The NSS endmember correlates the existence of tholins within certain units, mostly those coating the low-latitude mountain ranges that are co-latitudinal with the tholin-covered Cthulhu Macula. The spectral analysis has also revealed compositional differences between the handful of occurrences of northern non-cellular plains and the surrounding cellular plains, all of which are located within the portion of Sputnik Planitia that is presently experiencing net sublimation of volatiles, and which do not therefore exhibit a surface layer of bright, freshly-deposited N2 ice. The compositional differences between the cellular and non-cellular plains here hint at the effectiveness of convection in entraining and trapping tholins within the body of the cellular plains, while preventing the spread of such tholins to abutting non-cellular plains.

Published
2021
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26. Testing tholins as analogues of the dark reddish material covering Pluto’s Cthulhu region

Author

Bernard Schmitt, Silvia Protopapa, Dale P. Cruikshank, Alan Stern, Olivier Poch, Véronique Vuitton, C. M. Dalle Ore, Tanguy Bertrand, Lora Jovanovic, Leslie A. Young, Marie Fayolle, Thomas Gautier, Nathalie Carrasco, Eric Quirico, Will Grundy, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Delft University of Technology (TU Delft), PLANETO - 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), Lowell Observatory [Flagstaff], Southwest Research Institute [Boulder] (SwRI), NASA Ames Research Center (ARC), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), European Project: 636829,H2020,ERC-2014-STG,PRIMCHEM(2015), 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Lipides - Nutrition - Cancer (U866) (LNC), Université de Bourgogne (UB)-Institut National de la Santé et de la Recherche Médicale (INSERM)-AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement-Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation de Dijon (ENSBANA), 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), École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris)

Subjects
Materials science, 010504 meteorology & atmospheric sciences, Pluto's Cthulhu region, Continuum (design consultancy), [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Pluto’s Cthulhu region, Astrophysics, 01 natural sciences, Tholins, Atmosphere, New Horizons, symbols.namesake, 0103 physical sciences, Radiative transfer, Absorption (electromagnetic radiation), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Single-scattering albedo, Astronomy and Astrophysics, Tholin, Pluto, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, symbols, Titan (rocket family)
Abstract

International audience; New Horizons' reectance spectra of the Cthulhu dark belt of Pluto were modelled with tholins. Reectance factors, phase function and optical constants of these tholins were numerically determined from tholins' reectance measurements. Tholins do not reproduce the featureless spectra of Cthulhu. These results could suggest that this region is covered with a highly porous layer of organic aerosolsPluto’s fly-by by the New Horizons spacecraft in July 2015 has revealed a dark reddish equatorial region, named Cthulhu, covered by a dark, non-icy material whose origin and composition have yet to be determined. It has been suggested that this material could form from the sedimentation of photochemical aerosols, originating from dissociation and ionisation processes in Pluto’s high atmosphere (similarly to aerosols forming Titan’s haze). This hypothesis is here further investigated by comparing New Horizons spectra collected both in the visible and the near-infrared to laboratory reflectance measurements of analogues of Pluto’s aerosols (Pluto tholins). These aerosols were synthesised in conditions mimicking Pluto’s atmosphere, and their optical and reflectance properties were determined, before being used in Hapke models. In particular, the single scattering albedo and phase function of Pluto tholins were retrieved through Hapke model inversion, performed from laboratory reflectance spectra collected under various geometries. From reconstructed reflectance spectra and direct comparison with New Horizons data, some of these tholins are shown to reproduce the photometric level (i.e. reflectance continuum) reasonably well in the near-infrared. Nevertheless, a misfit of the red visible slope still remains and tholins absorption bands present in the modelled spectra are absent in those collected by the New Horizons instruments. Several hypotheses are considered to explain the absence of these absorption features in LEISA data, namely high porosity effects or GCR irradiation. The formation of highly porous structures, which is currently our preferred scenario, could be promoted by either sublimation of ices initially mixed with the aerosols, or gentle deposition under Pluto’s weak gravity.

Published
2021
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27. Investigations of grain size and abundance of NaCl on Europa’s surface through telescope observations and laboratory experiments: Implications for material transport from the interior to surface

Author

Shuya Tan, Hiroyuki Kurokawa, Dale P. Cruikshank, Yasuhito Sekine, Cristina M. Dalle Ore, and Masayuki Kuzuhara

Subjects
Telescope, Surface (mathematics), Materials science, law, Abundance (ecology), Mineralogy, Material transport, Grain size, law.invention
Published
2021
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28. On the origin & thermal stability of Arrokoth's and Pluto's ices

Author

Marc Neveu, Harold A. Weaver, Mohamed Ramy El-Maarry, J. M. Parker, John R. Spencer, William B. McKinnon, Scott A. Sandford, Alissa M. Earle, Orkan M. Umurhan, Mihaly Horanyi, Ralph L. McNutt, G. R. Gladstone, Andrew F. Cheng, Catherine B. Olkin, R. P. Binzel, Y. J. Pendleton, Carey M. Lisse, Olivier Mousis, William M. Grundy, Jj Kavelaars, J. T. Keane, N. Dello-Russo, Wladimir Lyra, Jordan K. Steckloff, S. A. Stern, Ivan Linscott, Bernard Schmitt, H. A. Elliott, Leslie A. Young, Dale P. Cruikshank, Daniel T. Britt, B. L. Lewis, J. M. Moore, Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Southwest Research Institute [Boulder] (SwRI), NASA Ames Research Center (ARC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Southwest Research Institute [San Antonio] (SwRI), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Physikalisches Institut [Bern], Universität Bern [Bern], Washington University in Saint Louis (WUSTL), Lowell Observatory [Flagstaff], Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Etudes Spatiales (CNES), NASA for financial support of the New Horizons project, Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, and Universität Bern [Bern] (UNIBE)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Solar System, 010504 meteorology & atmospheric sciences, Young stellar object, Comet, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Pluto, Outgassing, Stars, Supernova, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Trans-Neptunian object, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

We discuss in a thermodynamic, geologically empirical way the long-term nature of the stable majority ices that could be present in Kuiper Belt Object 2014 MU69 after its 4.6 Gyr residence in the EKB as a cold classical object. Considering the stability versus sublimation into vacuum for the suite of ices commonly found on comets, Centaurs, and KBOs at the average ~40K sunlit surface temperature of MU69 over Myr to Gyr, we find only 3 common ices that are truly refractory: HCN, CH3OH, and H2O (in order of increasing stability). NH3 and H2CO ices are marginally stable and may be removed by any positive temperature excursions in the EKB, as produced every 1e8 - 1e9 yrs by nearby supernovae and passing O/B stars. To date the NH team has reported the presence of abundant CH3OH and evidence for H2O on MU69s surface (Lisse et al. 2017, Grundy et al. 2020). NH3 has been searched for, but not found. We predict that future absorption feature detections will be due to an HCN or poly-H2CO based species. Consideration of the conditions present in the EKB region during the formation era of MU69 lead us to infer that it formed "in the dark", in an optically thick mid-plane, unable to see the nascent, variable, highly luminous Young Stellar Object-TTauri Sun, and that KBOs contain HCN and CH3OH ice phases in addition to the H2O ice phases found in their Short Period comet descendants. Finally, when we apply our ice thermal stability analysis to bodies/populations related to MU69, we find that methanol ice may be ubiquitous in the outer solar system; that if Pluto is not a fully differentiated body, then it must have gained its hypervolatile ices from proto-planetary disk sources in the first few Myr of the solar systems existence; and that hypervolatile rich, highly primordial comet C/2016 R2 was placed onto an Oort Cloud orbit on a similar timescale., Comment: 34 Pages, 5 Figures, 2 SOM Tables

Published
2021
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29. Spitzer's Solar System studies of asteroids, planets and the zodiacal cloud

Author

Alan W. Harris, Douglas P. Hamilton, Yanga R. Fernandez, William T. Reach, Anne J. Verbiscer, Dale P. Cruikshank, David E. Trilling, Yvonne Pendleton, Leigh N. Fletcher, Michael F. Skrutskie, Michael Mueller, Heidi B. Hammel, Carey M. Lisse, Joshua P. Emery, Glenn S. Orton, and Naomi Rowe-Gurney

Subjects
asteroids, Solar System, 010504 meteorology & atmospheric sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spitzer Space Telescope, planets, Neptune, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, infrared observations, zodiacal cloud, Zodiacal light, Uranus, Astronomy, Astronomy and Astrophysics, 13. Climate action, Asteroid, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Geology, Ice giant
Abstract

In its 16 years of scientific measurements, the Spitzer Space Telescope performed a number of groundbreaking and key infrared measurements of Solar System objects near and far. In this second of two Review Articles, we describe results from Spitzer observations of asteroids, dust rings and planets that provide new insight into the formation and evolution of our Solar System. The key Spitzer results presented here can be grouped into three broad classes: characterizing the physical properties of asteroids, notably including a large survey of near-Earth objects; detection and characterization of several dust/debris disks in the Solar System; and comprehensive characterization of ice giant (Uranus and Neptune) atmospheres. Many of these observations provide critical foundations for future infrared space-based observations. In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this second Review Article of a pair, Spitzer’s insight into asteroids, dust clouds and rings and the ice giant planets are summarized.

Published
2020

30. Evidence for ammonia-bearing species on the Uranian satellite Ariel supports recent geologic activity

Author

Chloe B. Beddingfield, Francesca Scipioni, Joshua P. Emery, Dale P. Cruikshank, William M. Grundy, Kevin P. Hand, Tom Nordheim, Joe Roser, and Richard Cartwright

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, Photon, Spectral signature, 010504 meteorology & atmospheric sciences, Uranus, FOS: Physical sciences, Magnetosphere, Astronomy and Astrophysics, Cosmic ray, Astrophysics, medicine.disease_cause, 01 natural sciences, Charged particle, Spectral line, Space and Planetary Science, 0103 physical sciences, medicine, 010303 astronomy & astrophysics, Ultraviolet, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

We investigated whether ammonia-rich constituents are present on the surface of the Uranian moon Ariel by analyzing 32 near-infrared reflectance spectra collected over a wide range of sub-observer longitudes and latitudes. We measured the band areas and depths of a 2.2-{\micron} feature in these spectra, which has been attributed to ammonia-bearing species on other icy bodies. Ten spectra display prominent 2.2-{\micron} features with band areas and depths > 2{\sigma}. We determined the longitudinal distribution of the 2.2-{\micron} band, finding no statistically meaningful differences between Ariel's leading and trailing hemispheres, indicating that this band is distributed across Ariel's surface. We compared the band centers and shapes of the five Ariel spectra displaying the strongest 2.2-{\micron} bands to laboratory spectra of various ammonia-bearing and ammonium-bearing species, finding that the spectral signatures of the Ariel spectra are best matched by ammonia-hydrates and flash frozen ammonia-water solutions. Our analysis also revealed that four Ariel spectra display 2.24-{\micron} bands (> 2{\sigma} band areas and depths), with band centers and shapes that are best matched by ammonia ice. Because ammonia should be efficiently removed over short timescales by ultraviolet photons, cosmic rays, and charged particles trapped in Uranus' magnetosphere, the possible presence of this constituent supports geologic activity in the recent past, such as emplacement of ammonia-rich cryolavas and exposure of ammonia-rich deposits by tectonism, impact events, and mass wasting.

Published
2020

31. Organic Components of Small Bodies in the Outer Solar System: Some Results of the New Horizons Mission

Author

William M. Grundy, Dale P. Cruikshank, and Yvonne J. Pendleton

Subjects
Solar System, Kuiper Belt object, 010504 meteorology & atmospheric sciences, protoplanetary disk, Review, Protoplanetary disk, 01 natural sciences, Charon, General Biochemistry, Genetics and Molecular Biology, Astrobiology, Atmosphere, New Horizons, Arrokoth, 0103 physical sciences, lcsh:Science, 010303 astronomy & astrophysics, Ecology, Evolution, Behavior and Systematics, Refractory (planetary science), 0105 earth and related environmental sciences, complex organics, Pluto, Paleontology, Accretion (astrophysics), solar nebula, Space and Planetary Science, lcsh:Q, Formation and evolution of the Solar System, Space environment
Abstract

The close encounters of the Pluto–Charon system and the Kuiper Belt object Arrokoth (formerly 2014 MU69) by NASA’s New Horizons spacecraft in 2015 and 2019, respectively, have given new perspectives on the most distant planetary bodies yet explored. These bodies are key indicators of the composition, chemistry, and dynamics of the outer regions of the Solar System’s nascent environment. Pluto and Charon reveal characteristics of the largest Kuiper Belt objects formed in the dynamically evolving solar nebula inward of ~30 AU, while the much smaller Arrokoth is a largely undisturbed relic of accretion at ~45 AU. The surfaces of Pluto and Charon are covered with volatile and refractory ices and organic components, and have been shaped by geological activity. On Pluto, N2, CO and CH4 are exchanged between the atmosphere and surface as gaseous and condensed phases on diurnal, seasonal and longer timescales, while Charon’s surface is primarily inert H2O ice with an ammoniated component and a polar region colored with a macromolecular organic deposit. Arrokoth is revealed as a fused binary body in a relatively benign space environment where it originated and has remained for the age of the Solar System. Its surface is a mix of CH3OH ice, a red-orange pigment of presumed complex organic material, and possibly other undetected components.

Published
2020

32. The Geology and Geophysics of Kuiper Belt Object (486958) Arrokoth

Author

Harold A. Weaver, J. Wm. Parker, Paolo Tanga, Stuart J. Robbins, Harold J. Reitsema, Carver J. Bierson, Dennis C. Reuter, Matthew E. Hill, Dale P. Cruikshank, Stephen Gwyn, Mark R. Showalter, Alex Parker, B. H. May, William M. Grundy, Oliver L. White, Douglas P. Hamilton, Orkan M. Umurhan, M. Mountain, Jj Kavelaars, Kelsi N. Singer, Alan D. Howard, David E. Trilling, E. Bernardoni, Ross A. Beyer, Ralph L. McNutt, D. Borncamp, John Stansberry, Simon B. Porter, Chloe B. Beddingfield, L. H. Wasserman, Bonnie J. Buratti, J. T. Keane, C. Fuentes, Ivan Linscott, Anne J. Verbiscer, Jean-Marc Petit, D. E. Jennings, A. L. Chaikin, Paul M. Schenk, Leslie A. Young, M. R. Piquette, Marc W. Buie, Catherine B. Olkin, Carly Howett, Mihaly Horanyi, Tod R. Lauer, Veronica J. Bray, Richard P. Binzel, Carey M. Lisse, Jeffrey M. Moore, Scott S. Sheppard, Silvia Protopapa, J. R. Spencer, William B. McKinnon, A. Y. Abedin, Kirby Runyon, G. R. Gladstone, S. A. Stern, Tetsuharu Fuse, Susan D. Benecchi, Rajani D. Dhingra, I. N. Reid, Mohamed Ramy El-Maarry, Martin Pätzold, H. A. Elliott, Amanda M. Zangari, Jason D. Hofgartner, H. Karoji, T. Stryk, Henry B. Throop, M. J. Kinczyk, Matthew J. Holman, David E. Kaufmann, A. F. Cheng, Daniel T. Britt, David J. McComas, David J. Tholen, Southwest Research Institute [Boulder] (SwRI), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Massachusetts Institute of Technology (MIT), Southwest Research Institute [San Antonio] (SwRI), Lowell Observatory [Flagstaff], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], NASA Goddard Space Flight Center (GSFC), NRC Herzberg Institute of Astrophysics, National Research Council of Canada (NRC), Princeton University, Rhenish Institute for Environmental Research (RIU), University of Cologne, Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Flagstaff], and Northern Arizona University [Flagstaff]

Subjects
Solar System, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Contact binary, 01 natural sciences, Impact crater, Neptune, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Multidisciplinary, Spacecraft, business.industry, Geophysics, Radius, Accretion (astrophysics), es, 13. Climate action, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Formation and evolution of the Solar System, business, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

Examining Arrokoth The New Horizons spacecraft flew past the Kuiper Belt object (486958) Arrokoth (also known as 2014 MU 69 ) in January 2019. Because of the great distance to the outer Solar System and limited bandwidth, it will take until late 2020 to downlink all the spacecraft's observations back to Earth. Three papers in this issue analyze recently downlinked data, including the highest-resolution images taken during the encounter (see the Perspective by Jewitt). Spencer et al. examined Arrokoth's geology and geophysics using stereo imaging, dated the surface using impact craters, and produced a geomorphological map. Grundy et al. investigated the composition of the surface using color imaging and spectroscopic data and assessed Arrokoth's thermal emission using microwave radiometry. McKinnon et al. used simulations to determine how Arrokoth formed: Two gravitationally bound objects gently spiraled together during the formation of the Solar System. Together, these papers determine the age, composition, and formation process of the most pristine object yet visited by a spacecraft. Science , this issue p. eaay3999 , p. eaay3705 , p. eaay6620 ; see also p. 980

Published
2020
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33. Cryovolcanic Flooding in Viking Terra on Pluto

Author

James Tuttle Keane, Jeffrey M. Moore, S. Alan Stern, Bernard Schmitt, William M. Grundy, Chloe B. Beddingfield, Kirby Runyon, Ross A. Beyer, Dale P. Cruikshank, Francesca Scipioni, Kimberly Ennico, Leslie A. Young, Oliver L. White, Harold A. Weaver, Catherine B. Olkin, Tanguy Bertrand, Stuart J. Robbins, Cristina M. Dalle Ore, NASA Ames Research Center (ARC), Lowell Observatory [Flagstaff], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Southwest Research Institute [Boulder] (SwRI), and Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL)

Subjects
Spectral signature, 010504 meteorology & atmospheric sciences, Pluto, Ices, Trough (geology), [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mineralogy, Astronomy and Astrophysics, Tholin, Terrain, Volcanism, Spectral bands, 01 natural sciences, Surface, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, Impact crater, 13. Climate action, Space and Planetary Science, IR spectroscopy, 0103 physical sciences, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

International audience; A prominent fossa trough (Uncama Fossa) and adjacent 28-km diameter impact crater (Hardie) in Pluto’s Viking Terra, as seen in the high-resolution images from the New Horizons spacecraft, show morphological evidence of in-filling with a material of uniform texture and red-brown color. A linear fissure parallel to the trough may be the source of a fountaining event yielding a cryoclastic deposit having the same composition and color properties as is found in the trough and crater. Spectral maps of this region with the New Horizons LEISA instrument reveal the spectral signature of H2O ice in these structures and in distributed patches in the adjacent terrain in Viking Terra. A detailed statistical analysis of the spectral maps shows that the colored H2O ice filling material also carries the 2.2-μm signature of an ammoniated component that may be an ammonia hydrate (NH3⋅nH2O) or an ammoniated salt. This paper advances the view that the crater and fossa trough have been flooded by a cryolava debouched from Pluto’s interior along fault lines in the trough and in the floor of the impact crater. The now frozen cryolava consisted of liquid H2O infused with the red-brown pigment presumed to be a tholin, and one or more ammoniated compounds. Although the abundances of the pigment and ammoniated compounds entrained in, or possibly covering, the H2O ice are unknown, the strong spectral bands of the H2O ice are clearly visible. In consideration of the factors in Pluto’s space environment that are known to destroy ammonia and ammoniawater mixtures, the age of the exposure is of order

Published
2020
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34. ICE CHEMISTRY ON OUTER SOLAR SYSTEM BODIES: ELECTRON RADIOLYSIS OF N

Author

Christopher K, Materese, Dale P, Cruikshank, Scott A, Sandford, Hiroshi, Imanaka, and Michel, Nuevo

Subjects
Article
Abstract

Radiation processing of the surface ices of outer Solar System bodies may be an important process for the production of complex chemical species. The refractory materials resulting from radiation processing of known ices are thought to impart to them a red or brown color, as perceived in the visible spectral region. In this work, we analyzed the refractory materials produced from the 1.2-keV electron bombardment of low-temperature N(2)-, CH(4)-, and CO-containing ices (100:1:1), which simulates the radiation from the secondary electrons produced by cosmic ray bombardment of the surface ices of Pluto. Despite starting with extremely simple ices dominated by N(2), electron irradiation processing results in the production of refractory material with complex oxygen- and nitrogen-bearing organic molecules. These refractory materials were studied at room temperature using multiple analytical techniques including Fourier-transform infrared spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and gas chromatography coupled with mass spectrometry (GC-MS). Infrared spectra of the refractory material suggest the presence of alcohols, carboxylic acids, ketones, aldehydes, amines, and nitriles. XANES spectra of the material indicate the presence of carboxyl groups, amides, urea, and nitriles, and are thus consistent with the IR data. Atomic abundance ratios for the bulk composition of these residues from XANES analysis show that the organic residues are extremely N-rich, having ratios of N/C ~ 0.9 and O/C ~ 0.2. Finally, GC-MS data reveal that the residues contain urea as well as numerous carboxylic acids, some of which are of interest for prebiotic and biological chemistries.

Published
2020

35. Disk-resolved Photometric Properties of Pluto and the Coloring Materials across its Surface

Author

Thomas Gautier, Catherine B. Olkin, Simon B. Porter, Leslie A. Young, Kim Ennico, Alan Stern, Dale P. Cruikshank, Jian-Yang Li, Jason C. Cook, Francesca Scipioni, Eric Quirico, Kelsi N. Singer, Ross A. Beyer, H. A. Weaver, Carly Howett, Anne J. Verbiscer, Silvia Protopapa, Cristina M. Dalle Ore, William M. Grundy, Dennis C. Reuter, Southwest Research Institute [Boulder] (SwRI), Lowell Observatory [Flagstaff], Planetary Science Institute [Tucson] (PSI), University of Virginia [Charlottesville], NASA Ames Research Center (ARC), 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), 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), Pinhead Institute, NASA Goddard Space Flight Center (GSFC), Search for Extraterrestrial Intelligence Institute (SETI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), 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), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Tholin, Astrophysics, Albedo, 01 natural sciences, Spectral line, Pluto, Atmosphere, Atmospheric radiative transfer codes, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Spectral slope, 010303 astronomy & astrophysics, Radiometric calibration, 0105 earth and related environmental sciences
Abstract

International audience; A multiwavelength regionally dependent photometric analysis of Pluto's anti-Charon-facing hemisphere using images collected by New Horizons' Multispectral Visible Imaging Camera (MVIC) reveals large variations in the absolute value and spectral slope of the single-scattering albedo. Four regions of interest are analyzed: the dark equatorial belt, Pluto's north pole, nitrogen-rich regions, and the mid-latitude terrains. Regions dominated by volatile ices such as Lowell Regio and Sputnik Planitia present single-scattering albedos of ~0.98 at 492 nm, almost neutral across MVIC's visible wavelength range (400–910 nm), indicating limited contributions from tholin materials. Pluto's dark equatorial regions, informally named Cthulhu and Krun Maculae, have single-scattering albedos of ~0.16 at 492 nm and are the reddest regions. Applying the Hapke radiative transfer model to combined MVIC and Linear Etalon Imaging Spectral Array (LEISA) spectra (400–2500 nm) of Cthulhu Macula and Lowell Regio successfully reproduces the spectral properties of these two regions of dramatically disparate coloration, composition, and morphology. Since this model uses only a single coloring agent, very similar to the Titan-like tholin of Khare et al., to account for all of Pluto's colors, this result supports the Grundy et al. conclusion that Pluto's coloration is the result of photochemical products mostly produced in the atmosphere. Although cosmic rays and extreme ultraviolet photons reach Pluto's surface where they can drive chemical processing, observations of diverse surface colors do not require different chemical products produced in different environments. We report a correction scaling factor in the LEISA radiometric calibration of 0.74 ± 0.05.

Published
2020
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36. Color, Composition, and Thermal Environment of Kuiper Belt Object (486958) Arrokoth

Author

Catherine B. Olkin, Dale P. Cruikshank, Simon B. Porter, Orkan M. Umurhan, Allen Lunsford, Silvia Protopapa, M. Ruaud, James Tuttle Keane, A. F. Cheng, Alex Parker, Mihaly Horanyi, Eric Quirico, Mark R. Showalter, Jeffrey M. Moore, D. E. Jennings, G. R. Gladstone, Francesca Scipioni, Bernard Schmitt, Amanda M. Zangari, Matthew E. Hill, Carly Howett, Ralph L. McNutt, S. A. Stern, John R. Spencer, William B. McKinnon, Marc W. Buie, L. Gabasova, Paul M. Schenk, D. C. Reuter, Kelsi N. Singer, G. Weigle, Anne J. Verbiscer, Joel Wm. Parker, Daniel T. Britt, Michael K. Bird, David J. McComas, H. A. Weaver, Leslie A. Young, H. A. Elliott, A. M. Earle, Yvonne J. Pendleton, Richard P. Binzel, Jason C. Cook, Ivan Linscott, William M. Grundy, Sebastiaan Krijt, C. M. Dalle Ore, Bonnie J. Buratti, Jj Kavelaars, Lowell Observatory [Flagstaff], NASA Ames Research Center (ARC), Southwest Research Institute [Boulder] (SwRI), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), French Centre National d'Etudes Spatiales (CNES), and Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences

Subjects
Solar System, Materials science, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mineralogy, chemistry.chemical_element, FOS: Physical sciences, Radiation, 01 natural sciences, Spectral line, Methane, Kuiper belt, chemistry.chemical_compound, ices, Arrokoth, 0103 physical sciences, Thermal, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, 2014 MU69, methanol, Earth and Planetary Astrophysics (astro-ph.EP), CH3OH, Multidisciplinary, surface composition, New Horizons spacecraft, color, chemistry, 13. Climate action, Brightness temperature, Astrophysics::Earth and Planetary Astrophysics, Carbon, Microwave, Astrophysics - Earth and Planetary Astrophysics
Abstract

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU69) has been largely undisturbed since its formation. We studied its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through irradiation of simple molecules. Water ice was not detected. This composition indicates hydrogenation of carbon monoxide-rich ice and/or energetic processing of methane condensed on water ice grains in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, which suggests that Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29 ± 5 kelvin. ©2020, NASA (contract no. NASW-02008), NASA (grant no. NAS5-97271 / TaskOrder30)

Published
2020
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37. Organic Molecules in the Icy Bodies of Planetary Systems – Accepted Notions and New Ideas

Author

Irakli Simonia and Dale P. Cruikshank

Subjects
chemistry.chemical_classification, Physics, 010504 meteorology & atmospheric sciences, Astronomy, Prebiotic evolution, ice, QB1-991, Astronomy and Astrophysics, prebiotic evolution, Planetary system, 01 natural sciences, Organic molecules, Astrobiology, planets, chemistry, Space and Planetary Science, Planet, 0103 physical sciences, Organic matter, comets, 010303 astronomy & astrophysics, organic matter, 0105 earth and related environmental sciences
Abstract

Cometary bodies are acknowledged to contain some of the most pristine matter in the Solar System, including ices and minerals. Certain number of previously unidentified spectral emission features detected in comets can be explained as emission by hydrocarbon molecules enclosed in a Shpolskii matrix and forming frozen hydrocarbon particles. UV-induced photoluminescence spectra of several self-organized molecules exhibit emission lines coincident with unidentified cometary lines, and open the possibility of the presence of this complex organic as components of the pristine organic inventory of comets. Complex organic was detected also in three satellites of Saturn. We describe in this paper results of our investigation of complex organic of the small bodies and present new approaches and hypotheses.

Published
2018
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38. Asteroid (16) Psyche: Evidence for a silicate regolith from spitzer space telescope spectroscopy

Author

Joshua P. Emery, Humberto Campins, Zoe A. Landsman, Dale P. Cruikshank, Josef Hanus, and Lucy F. Lim

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Regolith, Silicate, Psyche, chemistry.chemical_compound, Spitzer Space Telescope, Meteorite, chemistry, Space and Planetary Science, Asteroid, 0103 physical sciences, Emissivity, Protoplanet, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

Asteroid (16) Psyche is a unique, metal-rich object belonging to the “M” taxonomic class. It may be a remnant protoplanet that has been stripped of most silicates by a hit-and-run collision. Because Psyche offers insight into the planetary formation process, it is the target of NASA’s Psyche mission, set to launch in 2023. In order to constrain Psyche’s surface properties, we have carried out a mid-infrared (5–14 µm) spectroscopic study using data collected with the Spitzer Space Telescope’s Infrared Spectrograph. Our study includes two observations covering different rotational phases. Using thermophysical modeling, we find that Psyche’s surface is smooth and likely has a thermal inertia Γ = 5–25 J/m2/K/s1/2 and bolometric emissivity ϵ = 0.9, although a scenario with ϵ = 0.7 and thermal inertia up to 95 J/m2/K/s1/2 is possible if Psyche is somewhat larger than previously determined. The smooth surface is consistent with the presence of a metallic bedrock, which would be more ductile than silicate bedrock, and thus may not readily form boulders upon impact events. From comparisons with laboratory spectra of silicate and meteorite powders, Psyche’s 7–14 µm emissivity spectrum is consistent with the presence of fine-grained (

Published
2018
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39. Bladed Terrain on Pluto: Possible origins and evolution

Author

William B. McKinnon, Harold A. Weaver, Paul M. Schenk, Kimberly Ennico, Alissa M. Earle, Oliver L. White, Alan D. Howard, Francesca Scipioni, Leslie A. Young, Dale P. Cruikshank, Kelsi N. Singer, Bernard Schmitt, Geoffrey C. Collins, John R. Spencer, S. Alan Stern, Francis Nimmo, Silvia Protopapa, François Forget, Jeffrey M. Moore, David P. Hinson, Ross A. Beyer, William M. Grundy, Orkan M. Umurhan, Tanguy Bertrand, and Catherine B. Olkin

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Landform, Equator, Astronomy and Astrophysics, Terrain, Atmospheric sciences, 01 natural sciences, Surface conditions, Latitude, Pluto, Space and Planetary Science, High elevation, 0103 physical sciences, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

Bladed Terrain on Pluto consists of deposits of massive CH 4 , which are observed to occur within latitudes 30° of the equator and are found almost exclusively at the highest elevations (> 2 km above the mean radius). Our analysis indicates that these deposits of CH 4 preferentially precipitate at low latitudes where net annual solar energy input is lowest. CH 4 and N 2 will both precipitate at low elevations. However, since there is much more N 2 in the atmosphere than CH 4 , the N 2 ice will dominate at these low elevations. At high elevations the atmosphere is too warm for N 2 to precipitate so only CH 4 can do so. We conclude that following the time of massive CH 4 emplacement; there have been sufficient excursions in Pluto's climate to partially erode these deposits via sublimation into the blades we see today. Blades composed of massive CH 4 ice implies that the mechanical behavior of CH 4 can support at least several hundred meters of relief at Pluto surface conditions. Bladed Terrain deposits may be widespread in the low latitudes of the poorly seen sub-Charon hemisphere, based on spectral observations. If these locations are indeed Bladed Terrain deposits, they may mark heretofore unrecognized regions of high elevation.

Published
2018
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40. Ices on Charon: Distribution of H2O and NH3 from New Horizons LEISA observations

Author

William M. Grundy, Leslie A. Young, Silvia Protopapa, Dale P. Cruikshank, Harold A. Weaver, Jason C. Cook, C. Morea Dalle Ore, A. J. Verbiscer, S. A. Stern, Kimberly Ennico, and Catherine B. Olkin

Subjects
New horizons, 010504 meteorology & atmospheric sciences, Astronomy, Astronomy and Astrophysics, Tholin, 01 natural sciences, Pluto, Wavelength, Impact crater, Space and Planetary Science, 0103 physical sciences, Radiative transfer, Trans-Neptunian object, Ejecta, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

Charon, the largest moon of Pluto, appeared as a fairly homogeneous, gray, icy world to New Horizons during closest approach on July 14th, 2015. Charon's sub-Pluto hemisphere was scanned by the Ralph/LEISA near-IR spectrograph providing an unprecedented opportunity to measure its surface composition. We apply a statistical clustering tool to identify spectrally distinct terrains and a radiative transfer approach to study the variations of the 2.0-µm H2O ice band. We map the distribution of the ices previously reported to be present on Charon's surface, namely H2O and the products of NH3 in H2O. We find that H2O ice is mostly in the crystalline phase, confirming previous studies. The regions with the darkest albedos show the strongest signature of amorphous-phase ice, although the crystalline component is still strong. The brighter albedo regions, often corresponding to crater ejecta blankets, are characterized by larger H2O grains, possibly an indication of a younger age. We observe two different behaviors for the two absorption bands representing NH3 in H2O. The 2.21-µm band tends to cluster more in the northern areas compared to the ∼2.01-µm band. Both bands are present in the brighter crater rays, but not all craters show both bands. The 2.21-µm band is also clearly present on the smaller moons Hydra and Nix. These results hint that different physical conditions may determine the appearance or absence of these two different forms of NH3 in H2O ice in the Pluto system. We also investigate the blue slope affecting the spectrum at wavelengths longer than ∼1.8 µm previously reported by several authors. We find that the slope is common among the objects in the Pluto system, Charon, the smaller moons Nix and Hydra, and the darkest terrains on Pluto. It also characterizes the analog ice tholin obtained from irradiation of Pluto-specific materials (a mixture of N2, CH4, and CO ices) in the laboratory. Our modeling results show that Pluto ice tholins are widespread almost uniformly on Charon suggesting a common distribution possibly part of the original reservoir of materials that made up Charon. This was irradiated over the years to yield the gray color characteristic of Charon today. On top of the ‘primordial’ Pluto ice tholin there is the redder component produced by irradiation of the CH4 provided by Pluto's atmospheric contribution as illustrated by Grundy et al. (2016a).

Published
2018
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41. The Infrared Complex Refractive Index of Amorphous Ammonia Ice at 40 K (1.43–22.73 μm) and Its Relevance to Outer Solar System Bodies

Author

Joseph E. Roser, Alessandra Ricca, Richard J. Cartwright, Cristina Dalle Ore, and Dale P. Cruikshank

Subjects
Geophysics, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Astronomy and Astrophysics
Abstract

A near-IR absorption band at 2.2 μm linked to ammonia-containing ice has been detected on icy bodies throughout the solar system and appears in the extensive volume of data for Pluto and Charon returned by New Horizons. This band is an important clue for understanding the abundance of ammonia and ammoniated compounds on the surface of outer solar system bodies and requires new laboratory data for its full analysis. To satisfy this data need, the complex refractive index of amorphous ammonia ice was calculated from experimental infrared transmission spectra with ice deposition and measurements conducted at 40 K, a characteristic surface temperature for outer solar system bodies. The measured imaginary part of the complex refractive index and associated band strength calculations are generally larger than prior published values for amorphous ammonia ice at 30 K. The complex refractive index for amorphous ammonia at 40 K computed in the mid-infrared region (2.5–22.73 μm) will also be valuable for interpreting observations of both solar system and astrophysical sources anticipated with the Near InfraRed Spectrograph and Mid-Infrared Instrument on the James Webb Space Telescope.

Published
2021
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42. Origin of the Pluto–Charon system: Constraints from the New Horizons flyby

Author

Jason C. Cook, Carver J. Bierson, William M. Grundy, William B. McKinnon, Harold A. Weaver, Dale P. Cruikshank, Catherine B. Olkin, J. M. Moore, S. A. Stern, Leslie A. Young, Alex Parker, Francis Nimmo, John R. Spencer, and K. Ennico Smith

Subjects
Solar System, 010504 meteorology & atmospheric sciences, Moons of Pluto, Astronomy, Astronomy and Astrophysics, Crust, 01 natural sciences, Accretion (astrophysics), Tidal locking, Astrobiology, Pluto, Space and Planetary Science, 0103 physical sciences, Streaming instability, Formation and evolution of the Solar System, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

New Horizon's accurate determination of the sizes and densities of Pluto and Charon now permit precise internal models of both bodies to be constructed. Assuming differentiated rock-ice structures, we find that Pluto is close to 2/3 solar-composition anhydrous rock by mass and Charon 3/5 solar-composition anhydrous rock by mass. Pluto and Charon are closer to each other in density than to other large (≳1000-km diameter) Kuiper belt bodies. Despite this, we show that neither the possible presence of an ocean under Pluto's water ice shell (and no ocean within Charon), nor enhanced porosity at depth in Charon's icy crust compared with that of Pluto, are sufficient to make Pluto and Charon's rock mass fractions match. All four small satellites (Styx, Nix, Kerberos, Hydra) appear much icier in comparison with either Pluto or Charon. In terms of a giant impact origin, both these inferences are most consistent with the relatively slow collision of partly differentiated precursor bodies (Canup, Astrophys. J. 141, 35, 2011). This is in turn consistent with dynamical conditions in the ancestral Kuiper belt, but implies that the impact precursors themselves accreted relatively late and slowly (to limit 26 Al and accretional heating). The iciness of the small satellites is not consistent with direct formation of the Pluto–Charon system from a streaming instability in the solar nebula followed by prompt collapse of gravitationally bound “pebble piles,” a proposed formation mechanism for Kuiper belt binaries (Nesvorný et al., Astron. J. 140, 785–793, 2010). Growth of Pluto-scale bodies by accretion of pebbles in the ancestral Kuiper belt is not ruled out, however, and may be needed to prevent the precursor bodies from fully differentiating, due to buried accretional heat, prior to the Charon-forming impact.

Published
2017
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43. Spectroscopy of Pluto and Its Satellites

Author

Bernard Schmitt, Cathy Olkin, D. C. Reuter, Dale P. Cruikshank, S. Alan Stern, Donald E. Jennings, Silvia Protopapa, and William M. Grundy

Subjects
Pluto, Spectroscopy, Geology, Astrobiology
Published
2019
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46. Probing the regoliths of the classical Uranian satellites: Are their surfaces mantled by a layer of tiny H2O ice grains?

Author

William M. Grundy, Dale P. Cruikshank, Chloe B. Beddingfield, Richard Cartwright, Joshua P. Emery, and Noemi Pinilla-Alonso

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Spectral signature, 010504 meteorology & atmospheric sciences, Infrared, Uranus, Stratification (water), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Moons of Uranus, Spatial distribution, 01 natural sciences, Physics::Geophysics, Wavelength, Spitzer Space Telescope, Space and Planetary Science, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Geology, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

We investigate whether the surfaces of the classical moons of Uranus are compositionally stratified, with a thin veneer of mostly tiny H2O ice grains (, To be published in Icarus [2019, accepted]. 10 tables and 7 figures

Published
2019

47. The distribution of H 2 O, CH 3 OH, and hydrocarbon-ices on Pluto: Analysis of New Horizons spectral images

Author

Dennis C. Reuter, Bernard Schmitt, Stephen C. Tegler, Anne J. Verbiscer, Harold A. Weaver, Cristina M. Dalle Ore, Jennifer Hanley, Kelsi N. Singer, Kimberly Ennico, Gerrick E. Lindberg, Fatima Alketbi, John Stansberry, S. Philippe, Donald E. Jennings, Richard P. Binzel, Catherine B. Olkin, Logan A. Pearce, Allen W. Lunsford, Carly Howett, Alissa M. Earle, Garrett Thompson, Alex Parker, S. Alan Stern, Jason C. Cook, Silvia Protopapa, Dale P. Cruikshank, William M. Grundy, Leslie A. Young, Southwest Research Institute [Boulder] (SwRI), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Centre Hospitalier de l'Université de Montréal (CHUM), 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), Steward observatory, University of Arizona, Department of Space Studies [Boulder], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Pinhead Institute, NASA Ames Research Center (ARC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université de Montréal (UdeM), 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]), and Centre National d'Etudes Spatiales (CNES)

Subjects
Materials science, 010504 meteorology & atmospheric sciences, Imaging spectrometer, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics, Surface Composition, 01 natural sciences, 7. Clean energy, Spectral line, Atmosphere, 0103 physical sciences, Absorption (electromagnetic radiation), Spectroscopy, 010303 astronomy & astrophysics, Image resolution, 0105 earth and related environmental sciences, Pluto, Infrared observations, Astronomy and Astrophysics, Amorphous solid, Surface, New Horizons mission, Surfaces, 13. Climate action, Space and Planetary Science, composition
Abstract

International audience; On July 14, 2015, the New Horizons spacecraft made its closest approach to Pluto at about 12,000 km from its surface (Stern et al., 2015). Using the LEISA (Linear Etalon Imaging Spectral Array) near-IR imaging spectrometer we obtained two scans across the encounter hemisphere of Pluto at 6-7 km/pixel resolution. By correlating each spectrum with a crystalline H 2 O-ice model, we find several sites on Pluto's surface that exhibit the 1.5, 1.65 and 2.0 µm absorption bands characteristic of H 2 O-ice in the crystalline phase. These sites tend to be isolated and small (≲ 5000 km 2 per site). We note a distinct near-IR blue slope over the LEISA wavelength range and asymmetries in the shape of the 2.0 µm H 2 O-ice band in spectra with weak CH 4-ice bands and strong H 2 O-ice bands. These characteristics are indicative of fine-grain (grain diameters < wavelength or ∼ 1 µm) H 2 O-ice, like that seen in the spectra of Saturnian rings and satellites. However, the best-fit Hapke models require small mass fractions (≲10 −3) of fine-grained H 2 O-ice that we can exchange for other refractory materials in the models with little change in χ 2 , which may mean that the observed blue slope is possibly not due to a fine-grained material but an unidentified material with a similar spectral characteristic. We use these spectra to test for the presence of amorphous H 2 O-ice and estimate crystalline-to-amorphous H 2 O-ice fractions between 30 and 100%, depending on the location. We also see evidence for heavy hydrocarbons via strong absorption at λ > 2.3 µm. Such heavy hydrocarbons are much less volatile than N 2 , CH 4 , and CO at Pluto temperatures. We test for CH 3 OH, C 2 H 6 , C 2 H 4 , and C 3 H 8-ices because they have known optical constants and these ices are likely to arise from UV and energetic particle bombardment of the N 2 , CH 4 , CO-rich surface and atmosphere. Finally, we attempt to estimate the surface temperature using optical constants of pure CH 4 , and H 2 O-ice and best-fit Hapke models. Our standard model gives temperature estimates between 40 and 90 K, while our models including amorphous H 2 O-ice give lower temperature estimates between 30 and 65 K.

Published
2019
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48. Recent cryovolcanism in Virgil Fossae on Pluto

Author

Catherine B. Olkin, Kelsi N. Singer, Richard Cartwright, Kimberly Ennico, Ross A. Beyer, Richard P. Binzel, Isamu Matsuyama, Kirby Runyon, Oliver L. White, James Tuttle Keane, Carey M. Lisse, Leslie A. Young, William B. McKinnon, Jeffrey M. Moore, Dale P. Cruikshank, S. Alan Stern, Dimitra Atri, G. Randall Gladstone, Alissa M. Earle, Bernard Schmitt, Harold A. Weaver, Orkan M. Umurhan, Tanguy Bertrand, John R. Spencer, Scott A. Sandford, Stuart J. Robbins, Cristina M. Dalle Ore, William M. Grundy, Jason C. Cook, NASA Ames Research Center (ARC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), California Institute of Technology (CALTECH), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), New York University [Abu Dhabi], NYU System (NYU), Department of Earth and Planetary Sciences [St Louis], Washington University in Saint Louis (WUSTL), Southwest Research Institute [Boulder] (SwRI), Lowell Observatory [Flagstaff], Pinhead Institute, Massachusetts Institute of Technology (MIT), and Southwest Research Institute [San Antonio] (SwRI)

Subjects
010504 meteorology & atmospheric sciences, Ices, Trough (geology), [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Organic chemistry, 01 natural sciences, Astrobiology, Impact crater, Lithosphere, 0103 physical sciences, 14. Life underwater, True polar wander, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, volcanism, Pluto, Interiors, Astronomy and Astrophysics, Tholin, Graben, Surface, 13. Climate action, Space and Planetary Science, IR spectroscopy, Formation and evolution of the Solar System
Abstract

International audience; The Virgil Fossae region on Pluto exhibits three spatially coincident properties that are suggestive of recent cryovolcanic activity over an area approximately 300 by 200 km. Situated in the fossae troughs or channels and in the surrounding terrain are exposures of H2O ice in which there is entrained opaque red-colored matter of unknown composition. The H2O ice is also seen to carry spectral signatures at 1.65 and 2.2 μm of NH3 in some form, possibly as a hydrate, an ammoniated salt, or some other compound. Model calculations of NH3 destruction in H2O ice by galactic cosmic rays suggest that the maximum lifetime of NH3 in the uppermost meter of the exposed surface is ~109 years, while considerations of Lyman-α ultraviolet and solar wind charged particles suggest shorter timescales by a factor of 10 or 10000. Thus, 109 y is taken as an upper limit to the age of the emplacement event, and it could be substantially younger. The red colorant in the ammoniated H2O in Virgil Fossae and surroundings may be a macromolecular organic material (tholin) thought to give color to much of Pluto's surface, but probably different in composition and age. Owing to the limited spectral range of the New Horizons imaging spectrometer and the signal precision of the data, apart from the H2O and NH3 signatures there are no direct spectroscopic clues to the chemistry of the strongly colored deposit on Pluto. We suggest that the colored material was a component of the fluid reservoir from which the material now on the surface in this region was erupted. Although other compositions are possible, if it is indeed a complex organic material it may incorporate organics inherited from the solar nebula, further processed in a warm aqueous environment inside Pluto. A planet-scale stress pattern in Pluto's lithosphere induced by true polar wander, freezing of a putative interior ocean, and surface loading has caused fracturing in a broad arc west of Sputnik Planitia, consistent with the structure of Virgil Fossae and similar extensional features. This faulting may have facilitated the ascent of fluid in subsurface reservoirs to reach the surface as flows and as fountains of cryoclastic materials, consistent with the appearance of colored, ammoniated H2O ice deposits in and around Virgil Fossae. Models of a cryoflow emerging from sources in Virgil Fossae indicate that the lateral extent of the flow can be several km (Umurhan et al., 2019). The deposit over the full length (> 200 km) of the main trough in the Virgil Fossae complex and extending through the north rim of Elliot crater and varying in elevation over a range of ~2.5 km, suggests that it debouched from multiple sources, probably along the length of the strike direction of the normal faults defining the graben. The source or sources of the ammoniated H2O are one or more subsurface reservoirs that may or may not connect to the global ocean postulated for Pluto's interior. Alternatives to cryovolcanism in producing the observed characteristics of the region around Virgil Fossae are explored in the discussion section of the paper.

Published
2019
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49. Prebiotic Chemistry of Pluto

Author

James Tuttle Keane, Kimberly Ennico, Harold A. Weaver, Francesca Scipioni, Catherine B. Olkin, S. A. Stern, Dale P. Cruikshank, Bernard Schmitt, Ross A. Beyer, C. M. Dalle Ore, Veronica J. Bray, Leslie A. Young, Christopher K. Materese, Penelope J. Boston, Yvonne J. Pendleton, Kirby Runyon, Michael E. Summers, William M. Grundy, Carey M. Lisse, NASA Ames Research Center (ARC), Lowell Observatory [Flagstaff], 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), Southwest Research Institute [Boulder] (SwRI), 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 ), and 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])

Subjects
Solar System, Extraterrestrial Environment, Spectrophotometry, Infrared, 010504 meteorology & atmospheric sciences, Pyrimidine, genetic structures, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], chemistry.chemical_element, 01 natural sciences, Astrobiology, Nucleobase, chemistry.chemical_compound, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Volatile Organic Compounds, Pluto, Atmosphere, Ice, Water, Tholin, Agricultural and Biological Sciences (miscellaneous), Nitrogen, Thymine, Pyrimidines, chemistry, Purines, 13. Climate action, Space and Planetary Science, Formation and evolution of the Solar System, Methane
Abstract

We present the case for the presence of complex organic molecules, such as amino acids and nucleobases, formed by abiotic processes on the surface and in near-subsurface regions of Pluto. Pluto's surface is tinted with a range of non-ice substances with colors ranging from light yellow to red to dark brown; the colors match those of laboratory organic residues called tholins. Tholins are broadly characterized as complex, macromolecular organic solids consisting of a network of aromatic structures connected by aliphatic bridging units (e.g., Imanaka et al., 2004; Materese et al., 2014, 2015). The synthesis of tholins in planetary atmospheres and in surface ices has been explored in numerous laboratory experiments, and both gas- and solid-phase varieties are found on Pluto. A third variety of tholins, exposed at a site of tectonic surface fracturing called Virgil Fossae, appears to have come from a reservoir in the subsurface. Eruptions of tholin-laden liquid H_2O from a subsurface aqueous repository appear to have covered portions of Virgil Fossae and its surroundings with a uniquely colored deposit (D.P. Cruikshank, personal communication) that is geographically correlated with an exposure of H_2O ice that includes spectroscopically detected NH_3 (C.M. Dalle Ore, personal communication). The subsurface organic material could have been derived from presolar or solar nebula processes, or might have formed in situ. Photolysis and radiolysis of a mixture of ices relevant to Pluto's surface composition (N_2, CH_4, CO) have produced strongly colored, complex organics with a significant aromatic content having a high degree of nitrogen substitution similar to the aromatic heterocycles pyrimidine and purine (Materese et al., 2014, 2015; Cruikshank et al., 2016). Experiments with pyrimidines and purines frozen in H_2O-NH_3ice resulted in the formation of numerous nucleobases, including the biologically relevant guanine, cytosine, adenine, uracil, and thymine (Materese et al., 2017). The red material associated with the H_2O ice may contain nucleobases resulting from energetic processing on Pluto's surface or in the interior. Some other Kuiper Belt objects also exhibit red colors similar to those found on Pluto and may therefore carry similar inventories of complex organic materials. The widespread and ubiquitous nature of similarly complex organic materials observed in a variety of astronomical settings drives the need for additional laboratory and modeling efforts to explain the origin and evolution of organic molecules. Pluto observations reveal complex organics on a small body that remains close to its place of origin in the outermost regions of the Solar System.

Published
2019
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50. Initial results from the New Horizons exploration of 2014 MU 69 , a small Kuiper Belt object

Author

J. Fischetti, S. Bhaskaran, Matthias Hahn, Karl Whittenburg, Derek S. Nelson, G. A. Griffith, Amanda M. Zangari, B. J. Buratti, James T. Keane, E. J. Lessac-Chenen, Ralph L. McNutt, Tiffany J. Finley, J. Scherrer, M. A. Ritterbush, M. M. Saina, G. Dunn, T. A. Hill, J. Van Eck, T. Stryk, J. M. Albers, D. C. Reuter, C. M. Dalle Ore, H. A. Elliott, D. J. Schultz, J. Andrews, Douglas P. Hamilton, M. H. Versteeg, Orkan M. Umurhan, Matthew E. Hill, Hai Nguyen, M. Simon, L. Gabasova, D. E. Jennings, D. J. Katz, J. E. Riedel, N. Behrooz, M. N. Fosbury, Henry B. Throop, A. J. Verbiscer, E. Bernardoni, Ross A. Beyer, C. Engelbrecht, Francesca Scipioni, H. L. Winters, Thomas H. Zurbuchen, Carey M. Lisse, Veronica J. Bray, M. G. Ryschkewitsch, Stuart J. Robbins, S. E. Jaskulek, M. C. Kochte, Thomas Mehoke, M. S. Lahr, M. J. Salinas, V. A. Mallder, S. P. Williams, B. H. May, D. M. Mages, C. C. Deboy, Simon B. Porter, Gerhard Kruizinga, Marc W. Buie, Jorge I. Nunez, John Hayes, Peter Kollmann, P. Dharmavaram, J. M. Moore, Darrell F. Strobel, John Stansberry, R. P. Binzel, H. M. Hart, Jillian Redfern, E. W. Stahlheber, H. K. Kang, James L. Green, Anthony F. Egan, Carly Howett, Fran Bagenal, Dale Stanbridge, Chris B. Hersman, C. L. Chavez, Debi Rose, J. Y. Pelgrift, Maria E. Banks, D. C. Schurr, Matthew R. Buckley, L. S. Turner, Ivan Linscott, Kaj E. Williams, J. Eisig, Mihaly Horanyi, Matthew Jones, Mark R. Showalter, William B. McKinnon, Leslie A. Young, E. J. Colwell, Daniel T. Britt, Kirby Runyon, David J. McComas, G. Weigle, Bernard Schmitt, Susan D. Benecchi, Alissa M. Earle, M. J. Kinczyk, Tod R. Lauer, M. R. Piquette, Lori S. Glaze, Carver J. Bierson, L. M. Burke, Brian Carcich, O. S. Custodio, A. Harch, Harold A. Weaver, Dale P. Cruikshank, Oliver L. White, L. E. Brown, William M. Grundy, G. K. Oxton, Chelsea L. Ferrell, David E. Kaufmann, Mohamed Ramy El-Maarry, K. A. Harmon, W. R. Schlei, Eric Quirico, Derek C. Richardson, J. M. Freeze, Jennifer Hanley, R. G. Shelton, Andrew J. Steffl, Mike Bird, H. W. Taylor, Harold J. Reitsema, Stamatios M. Krimigis, D. R. Boone, E. D. Fattig, A. L. Regiec, D. J. Rodgers, Jason D. Hofgartner, D. Velez, Catherine B. Olkin, Kelsi N. Singer, Brian Bauer, Carl J. Ercol, Martin Pätzold, Nicole Martin, Stewart Bushman, J. Firer, Allen W. Lunsford, R. W. Webbert, A. L. Chaikin, Alex Parker, C. A. Conrad, M. P. Conner, S. B. Cooper, Chloe B. Beddingfield, William M. Folkner, J. E. Lee, M. B. Tapley, G. R. Gladstone, D. A. Aguilar, Glen H. Fountain, Emma Birath, Rebecca Sepan, Jeremy Bauman, J. Wm. Parker, S. Weidner, J. R. Jensen, Jason C. Cook, Alan D. Howard, William M. Owen, Andrew F. Cheng, B. L. Enke, Sarah A. Hamilton, Tom Andert, K. B. Beisser, K. E. Bechtold, J. R. Wendel, Rajani D. Dhingra, Paul M. Schenk, Michael E. Summers, J. R. Spencer, D. W. Hals, Silvia Protopapa, A. C. Ocampo, Mark E. Holdridge, S. A. Stern, A. Taylor, R. M. Tedford, G. P. Keleher, Gabe Rogers, Frederic Pelletier, Jj Kavelaars, Yanping Guo, Jon Pineau, Steven J. Conard, Alice Bowman, A. Hosadurga, B. G. Williams, Michael Vincent, David Y. Kusnierkiewicz, Paul E. Rosendall, G. B. Lawrence, J. R. Stuart, M. M. Stothoff, Jr. D. S. Mehoke, Southwest Research Institute [Boulder] (SwRI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Lowell Observatory [Flagstaff], Space Physics Research Laboratory [Ann Arbor] (SPRL), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, SwRI Planetary Science Directorate [Boulder], Universitat de Lleida, Institut für Raumfahrttechnik, Universität der Bundeswehr München [Neubiberg], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Department of Space Studies [Boulder], Rheinische Friedrich-Wilhelms-Universität Bonn, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institute of Hydrology, NASA Goddard Space Flight Center (GSFC), Department of Physics, Chemistry and Biology [Linköping] (IFM), Linköping University (LIU), Africa Rice Center [Bénin] (AfricaRice), Africa Rice Center [Côte d'Ivoire] (AfricaRice), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Yonsei University, Galaxies, Etoiles, Physique, Instrumentation (GEPI), 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), Centre International de Hautes Etudes Agronomiques Méditerranéennes - Institut Agronomique Méditerranéen de Montpellier (CIHEAM-IAMM), Centre International de Hautes Études Agronomiques Méditerranéennes (CIHEAM), Princeton University, Reed College, Hanoi National University of Education (HNUE), Rhenish Institute for Environmental Research (RIU), University of Cologne, School of Earth, Atmospheric and Environmental Sciences [Manchester] (SEAES), University of Manchester [Manchester], ESA, Southwest Research Institute [San Antonio] (SwRI), NASA Ames Research Center (ARC), Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Johns Hopkins University (JHU), Institute of Physics of the Czech Academy of Sciences (FZU / CAS), Czech Academy of Sciences [Prague] (CAS), Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Department of Biochemistry, Faculty of Biology, University of Warmia and Mazury [Olsztyn], California Institute of Technology (CALTECH)-NASA, Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), University of Warmia and Mazury, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), 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 de Lille-Centre National de la Recherche Scientifique (CNRS), inconnu temporaire UPEMLV, Inconnu, INGENIERIE (INGENIERIE), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Génie des Procédés Plasmas et Traitement de Surface (ENSCP), PARIS, Africa Rice Center, Africa Rice Center (AfricaRice), Institut de pharmacologie moléculaire et cellulaire (IPMC), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), 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), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institute of Physics of Academy of Sciences of Czech Republic, and Czech Academy of Sciences [Prague] (ASCR)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Solar System, Multidisciplinary, 010504 meteorology & atmospheric sciences, Spacecraft, business.industry, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astronomy, Coma (optics), Contact binary, Albedo, 01 natural sciences, Object (philosophy), Solar wind, 13. Climate action, 0103 physical sciences, Pebble, business, 010303 astronomy & astrophysics, Geology, ComputingMilieux_MISCELLANEOUS, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observations. MU69 is a bi-lobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color and compositional heterogeneity. No evidence for satellites, ring or dust structures, gas coma, or solar wind interactions was detected. By origin MU69 appears consistent with pebble cloud collapse followed by a low velocity merger of its two lobes., 43 pages, 8 figure

Published
2019
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