National Aeronautics and Space Administration

The surface of and the interactions with the interior and the atmosphere from the analysis of Cassini VIMS and RADAR data Anezina Solomonidou1,2, A. Coustenis2, R. Lopes1, S. Rodriguez5, E. Bratsolis4, M. Malaska1, B. Schmitt7, P. Drossart2, C. Matsoukas4, M. Hirtzig3, R.H. Brown6, L. Maltagliati2

1NASA Jet Propulsion Laboratory, California Institute of Technology, California, USA, 2LESIA - Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot – Meudon, 92195 Meudon Cedex, France, 3Fondation La Main à la Pâte, Montrouge, France, 4Department of Physics, University of Athens, Athens, Greece, 5Laboratoire AIM, Université Paris Diderot, Paris 7/CNRS/CEA-Saclay, DSM/IRFU/SAp, Centre de l’Orme des Merisiers, bât. 709, 91191 Gif sur Yvette, France, 6Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA, 7Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble Cedex, France.

Introduction & Problem Selection of VIMS data with SAR as a base Data & Method VIMS Titan map at 2.03µm Regions of interest and pixel selection from top to bottom: hummocky terrains (hh), labyrinth terrain (lb), dunes (dl). The 1st column shows Titan, ’s largest the full VIMS datacube (R: 5.00mi, G: 2.03mi, B: 1.27mi) with Studying Titan’s surface observation geometries adequate for a plane-parallel approximation satellite, has a complex and good enough resolution (the red box surrounds the image shown requires specific tools atmosphere and surface, in the 2nd column). The 2nd column shows a zoom-in of the region making it a key area for of interest based on the equivalent SAR resolution that is showed in VIMS processed with Radiative the 3rd column; the red dot represent the center of location. Column planetary research. 4 is a combination of the figures showed in 2nd (R:2.03mi/1.28mi, Transfer code G:SAR, B:SAR) and 3rd column. ² aerosol and methane Understanding the interplay of opacity characteristics geologic processes on Titan is important for: All inferences of surface properties need to first account for the atmospheric contribution ² modelling the interior-surface- to the data. atmospheric interactions i. Undifferentiated Plains We evaluate whether surface ² finding the CH source 4 ii. Variable Plains features change appearance ² climate evolution iii. Streak-like Plains Selection of regions of interest (RoIs) iv. Hummocky terrains Selected regions of interest from the major geomorphological units with time accounting for ² Unveiling surface compositions v. Labyrinth terrains ² constraining habitability vi. Dunes on Titan as shown on Cassini VIMS mosaic map at 2.03 micron. vii. Candidate Evaporites The characterization of the areas is based on morphological and/or ² atmosphere spectral characteristics from studies by Lopes et al. (2010;2016), ix. Candidate Cryovolcanics ² surface albedo x. Alluvial Fans Barnes et al. (2013), Malaska et al. (2011;2016), Niesh et al. (2015), xi. Maculae Solomonidou et al. (2013;2014;2016), Radebaugh et al. (2016). ² Changes indicate active Geologically active areas xii. Impact Craters processes (possibly xiii. Scalloped Plains We use tools with updated parameters that have could be utilized as future endogenic) mission landing sites never been used before for the investigation of Titan’s surface. Solomonidou et al. (2014; 2016)

Temporal Evolution Of Surface Albedo (Wrt To HLS) Conclusions and Next Steps

Geomorphic Unit Groups Possible chemical Based on surface albedo extractions Tested areas Change in albedo compound RESULTS ✓ CO2 Group A: (disappearance of CO due to methane rainfall (2005-2009) 2 (Solomonidou et al. 2016) and cover up) Un. Plains Group A: Labyrinth Hotei Regio - Tholin-like ✗ Streak Plains (2004-2009) (Solomonidou et al. 2016) material ✓ Deposition or exposure of bright (2005-2006) material (Solomonidou et al. 2016) Group B: Group B: Blandlands ✗ 50-75% Tholin material (2010-2012) Hummocky Very dark (Solomonidou et al.; Lopes et al. 2016) Variable Plains material Test cases A,B,C ✗ Bitumen material HLS (dune fields 2005-2012) (Solomonidou et al. 2016) Dunes Labyrinth, 60-80% Tholin material Streak Plains, Ongoing 55% Tholin material Albedo As A Function Of Time Variable Plains (Solomonidou et al. in prep.) 50-70% Bitumen material Hummocky 40-65% Bitumen material Evaporitic candidates Ongoing - We tested the HLS (Yalaing, Hetpet, Concordia, (Solomonidou et al. in prep.) temporal evolution of: Adiri) HLS ongoing -

Un. Plains (2004-2012) (Sotin et al. in prep.) Cryo candidates ONGOING Dunes The results of this analysis will shed light on geological process Surrounding origination causing albedo changes with time.

Exogenic Processes Endogenic Processes Blandlands (2010-2012) Hotei Regio (2005-2009) ² Evaporitic, fluvial, or lacustrine ² Cryovolcanic deposits Tui Regio (2005-2009) deposits Sotra Patera (2004-2006) ² Brightening or darkening due to Test cases (dunes) ² no connection to the interior resurfacing of an initially cryovolcanic terrain ² precipitation of methane rain and/or tholins

RESULTS IMPORTANCE Blandlands NO CHANGE -energy Hotei Regio NO CHANGE -methane reservoir Tui Regio 50% DARKER -interior/surface/atmosphere exchanges Sotra Patera 2x BRIGHTER -support for life

From Solomonidou et al. (2016); Sotin et al. (2016)

National Aeronautics and Space Administration References Solomonidou et al. (2013). Planet. Space Sci. 77, 104–117. Malaska et al. (2011). 42nd Lunar and Planetary Science Conference, No. 1608, p.1567. Jet Propulsion Laboratory Solomonidou et al. (2014). JGR, 119, 1729-1747. Malaska et al. (2016). Icarus, 270, 130-161. California Institute of Technology Solomonidou et al. (2016). Icarus, 270, 85-99. Barnes et al. (2013). Planetary Science, 2, 1-22. Pasadena, California Lopes et al. (2010). Icarus, 205, 540-558. Radebaugh et al. (2016). Geological Society, London, Special Publications, 440.

Lopes et al. (2016). Icarus, 270, 162-182. Neish et al. (2015). Geophysical Research Letters, 42, 3746-3754. Sohl et al. (2014). JGR, 119, 1013-1036. Copyright 2016. All rights reserved. Sotin et al. (2016). In preparation.