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1. 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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2. 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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3. New Frontiers Titan Orbiter

Author

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

Subjects
Orbiter, symbols.namesake, law, spacecraft, symbols, decadal survey, White paper, Titan (rocket family), Titan, Geology, Astrobiology, law.invention
Published
2021

4. 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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5. Large catchment area recharges Titan’s Ontario Lacus

Author

Brian J. Yanites, Rajani D. Dhingra, Randolph L. Kirk, and Jason W. Barnes

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Meteorology, Drainage basin, Astronomy and Astrophysics, 01 natural sciences, Infiltration (hydrology), Space and Planetary Science, 0103 physical sciences, Area ratio, Physical geography, Catchment area, Precipitation, Surface runoff, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

We seek to address the question of what processes are at work to fill Ontario Lacus while other, deeper south polar basins remain empty. Our hydrological analysis indicates that Ontario Lacus has a catchment area spanning 5.5% of Titan’s surface and a large catchment area to lake surface area ratio. This large catchment area translates into large volumes of liquid making their way to Ontario Lacus after rainfall. The areal extent of the catchment extends to at least southern mid-latitudes (40°S). Mass conservation calculations indicate that runoff alone might completely fill Ontario Lacus within less than half a Titan year (1 Titan year = 29.5 Earth years) assuming no infiltration. Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of clouds over the southern mid and high-latitudes are consistent with precipitation feeding Ontario’s large catchment area. This far-flung rain may be keeping Ontario Lacus filled, making it a liquid hydrocarbon oasis in the relatively dry south polar region.

Published
2018
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6. Europa Clipper Preparatory Photometry to Constrain Surface Properties

Author

Bonnie J. Buratti, Rajani D. Dhingra, and Benoît Seignovert

Subjects
Photometry (astronomy), Geophysics, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Astronomy, Astronomy and Astrophysics, Clipper (electronics), Geology
Abstract

We infer the surface reflectance properties of Europa using multispectral data sets available from previous missions. We use 21 full-disk images of Europa from Voyager’s Imaging Science System, Galileo’s Solid State Imaging, and New Horizons’ Long Range Reconnaissance Imager at differing observation geometries (10°–128° (phase angle)) to compute disk-integrated surface-scattering properties over various geologic units. The derived empirical photometric models will serve the practical goals of data acquisition, aid in the calculation of instrument integration times, and facilitate quick-look data products for images acquired by Europa Clipper and other future missions to Europa. We use the Minneart and Lommel–Seeliger plus Lambert reflectance models to constrain the photometric parameters of Europa’s surface. We find that the surface albedo parameter, B 0, in the Minneart function gradually decreases with increasing phase angles. We also note that the photometric properties of Europa (geometric albedo at 0.47 μm is 0.72 on the leading side and 0.62 on the trailing side) require a significant “Lambert” term (A < 1) in the Lommel–Seeliger plus Lambert reflectance model. We also observe that the photometric parameters are not highly dependent on the geologic terrain type despite their visibly different albedos.

Published
2021
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7. 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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8. Observational Evidence for Summer Rainfall at Titan's North Pole

Author

Jason W. Barnes, P. D. Nicholson, Sebastien Rodriguez, Bonnie J. Burrati, Ralf Jauman, Elizabeth P. Turtle, Christophe Sotin, Kevin H. Baines, Don E. Jennings, Jason Perry, Roger N. Clark, Rajani D. Dhingra, Jason M. Soderblom, V. Cottini, Stéphane Le Mouélic, Robert H. Brown, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Cornell University [New York], MIT, Earth Atmospher & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA, DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), and NASA Goddard Space Flight Center (GSFC)

Subjects
North pole, ComputerSystemsOrganization_COMPUTERSYSTEMIMPLEMENTATION, 010504 meteorology & atmospheric sciences, GeneralLiterature_INTRODUCTORYANDSURVEY, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], ComputerApplications_COMPUTERSINOTHERSYSTEMS, 010502 geochemistry & geophysics, 01 natural sciences, Observational evidence, symbols.namesake, Geophysics, Climatology, symbols, General Earth and Planetary Sciences, Titan (rocket family), Geology, 0105 earth and related environmental sciences
Abstract

International audience; Methane rain on Saturn's moon Titan makes it the only place, other than Earth, where rain interacts with the surface. When and where that rain wets the surface changes seasonally in ways that remain poorly understood. Here we report the discovery of a bright ephemeral feature covering an area of 120,000 km 2 near Titan's north pole in observations from Cassini's near-infrared instrument, Visual and Infrared Mapping Spectrometer on 7 June 2016. Based on the overall brightness, spectral characteristics, and geologic context, we attribute this new feature to specular reflections from a rain-wetted solid surface like those off of a sunlit wet sidewalk. The reported observation is the first documented rainfall event at Titan's north pole and heralds the arrival of the northern summer (through climatic evidence), which has been delayed relative to model predictions. This detection helps constrain Titan's seasonal change and shows that the "wet-sidewalk effect can be used to identify other rain events." Plain Language Summary Cassini arrived in the Saturnian system in the southern summers of 2004. As expected, the Cassini team observed cloud cover, storms, and precipitation on the south pole. Like Earth, Titan has an axial tilt (27 •) and its seasons vary over its year (30 Earth years). Ever since this shift in season began, the Cassini team eagerly waited for observations indicating cloud cover and precipitation that went missing from the northern latitudes. Our rainfall observation at the north pole is a major finding for two important reasons. First, this discovery observation heralds the much awaited arrival of the north polar summer rainstorms on Titan. This atmospheric phenomenon has been delayed compared to the theoretical predictions and was perplexing Titan researchers and climate modelers especially because the north pole hosts most of Titan's lakes and seas. Second, it is extremely difficult to detect rainfall events on Titan due to its thick atmospheric haze and very limited opportunities to view the surface (and its changes). We have used a novel phenomenon-the smoothening of a previously dry, rough surface by a thin layer of fluid after rainfall, similar to a wet sidewalk-as evidence for rainfall events on the surface of Titan.

Published
2019
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9. Origins of pits and troughs and degradation on a small primitive planetesimal in the Kuiper Belt: high-resolution topography of (486958) Arrokoth (aka 2014 MU69) from New Horizons

Author

Kelsi N. Singer, Chloe B. Beddingfield, S. Alan Stern, John R. Spencer, Paul M. Schenk, Jeffrey M. Moore, Joel Wm. Parker, Catherine B. Olkin, Stuart J. Robbins, Anne J. Verbiscer, Rajani D. Dhingra, Tod R. Lauer, Hal Weaver, James T. Keane, William B. McKinnon, and Ross A. Beyer

Subjects
Planetesimal, 010504 meteorology & atmospheric sciences, Comet, Astronomy and Astrophysics, Icy moon, Fault scarp, 01 natural sciences, Paleontology, Impact crater, Space and Planetary Science, Planet, Micrometeorite, 0103 physical sciences, Hypervelocity, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

The dominant topographic features on two-lobed Kuiper Belt object (486958) Arrokoth (provisionally designated 2014 MU69) are scattered, small, circular depressions or pits up to ~1.0 km across and curvilinear troughs observed near the terminator during the New Horizons encounter of 01 January 2019. With important exceptions, evidence for an endogenic origin for pits is lacking and impact remains the most likely origin. Pit depths relative to the local surface are shallower than hypervelocity simple craters on icy moons and consistent with low velocity (~300 m/s) impacts in an icy target (the role of porosity and cohesion in cratering on Arrokoth being uncertain). There is, however, a large scatter in observed d/D, with some pits too shallow to measure reliably. The range of preservation states observed for both pits and troughs is consistent with slow but persistent degradation on the surface of this (and perhaps other) small primitive planetesimal(s) in the Kuiper Belt by agents such as micrometeorite bombardment or volatile loss, indicating that degradation does indeed occur on such bodies. Arrokoth pits could also be related to circular depressions on comet 9P/Tempel (though comparisons of surface features on Arrokoth and comets are intriguing they are limited by resolution differences and the evolved state of cometary surfaces). Two of the curvilinear troughs occur along the terminator of the Large Lobe. One trough is a shallow depression devoid of resolvable structures, the other features several linear scarps a few 10s of meters high, suggesting that coherent failure can occur on the surfaces of small Kuiper Belt objects such as Arrokoth. Several of the deepest small pits are also clustered within this walled trough, similar to tectonically associated pit chains on other planets. These pits and an obliquely viewed linear chain of elongate depressions remain the best candidates for endogenic features on Arrokoth. Subtle undulations and linear features no more than a few 10's of meters in amplitude (and even a few candidate positive relief features) are also evident in the terminator regions, indicating that the long-term evolution of this body may have been complex.

Published
2021
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10. Tidal Currents Detected in Kraken Mare Straits from Cassini VIMS Sun Glitter Observations

Author

Jason W. Barnes, Jason M. Soderblom, Benoît Seignovert, Rajani D. Dhingra, Michael Heslar, and Christophe Sotin

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), geography, Bedform, geography.geographical_feature_category, Sun glitter, FOS: Physical sciences, Sediment, Astronomy and Astrophysics, Crust, Inlet, Seafloor spreading, Geophysics, Tectonic uplift, Oceanography, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Bathymetry, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present Cassini VIMS observations of sun glitter -- wave-induced reflections from a liquid surface offset from a specular point -- on Kraken Mare. Sun glitter reveals rough sea surfaces around Kraken Mare, namely the coasts and narrow straits. The sun glitter observations indicate wave activity driven by the winds and tidal currents in Kraken Mare during northern summer. T104 Cassini VIMS observations show three sun glitter features in Bayta Fretum indicative of variegated wave fields. We cannot uniquely determine one source for the coastal Bayta waves, but we lean toward the interpretation of surface winds, because tidal currents should be too weak to generate capillary-gravity waves in Bayta Fretum. T105 and T110 observations reveal wave fields in the straits of Seldon Fretum, Lulworth Sinus, and Tunu Sinus that likely originate from the constriction of tidal currents. Coastlines of Bermoothes and Hufaidh Insulae adjoin rough sea surfaces, suggesting a complex interplay of wind-roughened seas and localized tidal currents. Bermoothes and Hufaidh Insulae may share characteristics of either the Torres Strait off Australia or the Aland region of Finland, summarized as an island-dense strait with shallow bathymetry that hosts complex surface circulation patterns. Hufaidh Insulae could host seafloor bedforms formed by tidal currents with an abundant sediment supply, similar to the Torres Strait. The coastlines of Hufaidh and Bermoothes Insulae likely host ria or flooded coastal inlets, suggesting the Insulae may be local peaks of primordial crust isolated by an episode of sea-level rise or tectonic uplift., Comment: Accepted to the Planetary Science Journal, 25 pages, 13 figures

Published
2020
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11. Spatio-temporal Variation of Bright Ephemeral Features on Titan’s North Pole

Author

Rajani D. Dhingra, Jason W. Barnes, Christophe Sotin, Stéphane Le Mouélic, Robert H. Brown, Philip D. Nicholson, Jason M. Soderblom, Sebastien Rodriguez, Bonnie J. Buratti, Roger N. Clark, Kevin H. Baines, Michael Heslar, and Ralf Jaumann

Subjects
North pole, symbols.namesake, Geophysics, Space and Planetary Science, Ephemeral key, Earth and Planetary Sciences (miscellaneous), symbols, Astronomy and Astrophysics, Titan (rocket family), Atmospheric sciences, Geology
Abstract

We identify and document the instances of bright ephemeral features (BEF)—bright areas that appear, disappear, and shift from flyby to flyby on Titan’s north pole, using the Cassini Visual and Infrared Mapping Spectrometer data set, thereby developing a sense of their spatial distribution and temporal frequency. We find that BEFs have differing geographic location and spatial extents. However, they have similar observation geometries and orders of surface area coverage and are mostly accompanied by specular reflections. We find the BEFs to represent either broad specular reflection off of a recently wetted surface on the north pole of Titan or a near-surface fog—both owing to probable recent rainfalls. Our surface model constrains the surface roughness to be of 9°–15° indicating the approximate vertical relief of the region to be that of cobbles. We also find that within less than two Titan days the BEF (if on the surface) might infiltrate into the subsurface. We hypothesize the parts of BEFs that extend into the maria to be precipitation fog.

Published
2020
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12. Landslides on Charon

Author

Paul M. Schenk, Rajani D. Dhingra, Kimberly Ennico, Kirby Runyon, Kelsi N. Singer, Veronica J. Bray, Chloe B. Beddingfield, New Horizons Team, Leslie A. Young, S. Alan Stern, William M. Grundy, Jeffrey M. Moore, John R. Spencer, Catherine B. Olkin, Harold A. Weaver, William B. McKinnon, and Ross A. Beyer

Subjects
New horizons, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Landslide, Fault scarp, 01 natural sciences, Pluto, Tectonics, Space and Planetary Science, 0103 physical sciences, Normal fault, Digital elevation model, 010303 astronomy & astrophysics, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

We investigated five large landslides identified in the Serenity Chasma region of Charon. The identification of these landslides involved a search for these features in images taken by cameras onboard the New Horizons spacecraft. Various landslide properties were analyzed based on their morphologies using a digital terrain model of the region. We found that landslides are confined to the walls of the large normal fault scarps that make up Serenity Chasma. Based on extensive landslide runout lengths (L) relative to their drop heights (H), we classified these features as long-runout landslides. By analyzing their geometries, we estimated the friction coefficients of the landslide material (H/L) to be between 0.15 to 0.31 and the runout efficiencies (L/H) to be between 3.2 and 6.8. We also estimated that the specific energy released during landslide motion ranged from 0.8 to 1.3 kJ kg−1. These amounts of energy were too low to have generated significant melt around landslide particles.

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

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

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, New horizons, 010504 meteorology & atmospheric sciences, Ultima, FOS: Physical sciences, Astronomy, 01 natural sciences, Object (philosophy), Geophysics, 0103 physical sciences, General Earth and Planetary Sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

The New Horizons encounter with the cold classical Kuiper Belt object 2014 MU69 (informally named “Ultima Thule,” hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the Kuiper Belt. Related to but not thought to have formed in the same region of the solar system as the comets that been explored so far, it will also be the most distant, and most primitive body yet visited by spacecraft. In this letter we begin with a brief overview of cold classical Kuiper Belt objects, of which Ultima is a prime example. We give a short preview of our encounter plans. We note what is currently known about Ultima from Earth-based observations. We then review our expectations and capabilities to evaluate Ultima's composition, surface geology, structure, near space environment, small moons, rings, and the search for activity. Plain language summary: The letter discusses the current state‐of‐knowledge for the cold classical Kuiper Belt object 2014 MU69, the target of a close encounter by NASA's New Horizon spacecraft on 1 January 2019. We also review our encounter plans and make broad speculative predictions as to might be revealed by our observations. New Horizons will fly to within 3,500 km of 2014 MU69 (informally named “Ultima Thule”), acquiring images with pixel scale resolutions significantly better than 100 m/pixel). We plan to obtain topography derived from stereo imaging and body shape. Our spectroscopic observations potentially could detect H2O, CH4, N2, CH3OH, and NH3, depending on their brightness and abundance on the surface. We will also search for evidence of outgassing, small moons, and rings. This exploration will transform Kuiper Belt and Kuiper Belt object science from a purely astronomical regime, to a geological and geophysical regime, which radically changed paradigms when the same happened to asteroids and comets in past decades. ©2018

Published
2018

15. Core-ion temperature measurement of the ADITYA tokamak using passive charge exchange neutral particle energy analyzer

Author

Santosh P. Pandya, J. Govindarajan, Rajani D. Dhingra, Kumar Ajay, and Priyanka Mishra

Subjects
Tokamak, Materials science, law, Electron temperature, Plasma diagnostics, Plasma, Atomic physics, Neutral particle, Instrumentation, Temperature measurement, Noise (electronics), ADITYA, law.invention
Abstract

Core-ion temperature measurements have been carried out by the energy analysis of passive charge exchange (CX) neutrals escaping out of the ADITYA tokamak plasma (minor radius, a = 25 cm and major radius, R = 75 cm) using a 45° parallel plate electrostatic energy analyzer. The neutral particle analyzer (NPA) uses a gas cell configuration for re-ionizing the CX-neutrals and channel electron multipliers (CEMs) as detectors. Energy calibration of the NPA has been carried out using ion-source and ΔE∕E of high-energy channel has been found to be ∼10%. Low signal to noise ratio (SNR) due to VUV reflections on the CEMs was identified during the operation of the NPA with ADITYA plasma discharges. This problem was rectified by upgrading the system by incorporating the additional components and arrangements to suppress VUV radiations and improve its VUV rejection capabilities. The noise rejection capability of the NPA was experimentally confirmed using a standard UV-source and also during the plasma discharges to get an adequate SNR (>30) at the energy channels. Core-ion temperature Ti(0) during flattop of the plasma current has been measured to be up to 150 eV during ohmically heated plasma discharges which is nearly 40% of the average core-electron temperature (typically Te(0) ∼ 400 eV). The present paper describes the principle of tokamak ion temperature measurement, NPA's design, development, and calibration along with the modifications carried out for minimizing the interference of plasma radiations in the CX-spectrum. Performance of the NPA during plasma discharges and experimental results on the measurement of ion-temperature have also been reported here.

Published
2013

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