CaSSIS colour imaging of late lava flows and hydrothermal alteration in Ladon Basin,

Daniel Mège1, Matteo Massironi2,3, Barbara De Toffoli2, Joanna Gurgurewicz1, Lucia Marinangeli3,4, Loredana Pompilio4, Riccardo Pozzobon2, Joel Davis5, Sylvain Douté6, Ernst Hauber7, Wlodek Kofman1, Maurizio Pajola3, Jason Perry8, Antoine Pommerol9, Frank Seelos10, Livio Tornabene11, Alice Lucchetti3, Alfred McEwen8, Gabriele Cremonese3, Nicolas Thomas9

(1) Space Research Centre PAS, Wrocław, Poland ([email protected]); Dipartimento di Geoscienze, Università di Padova, Italy, (3) INAF-Osservatorio Astronomico di Padova, Italy, (4) DiSPuTer Università d’Annunzio, Chieti, Italy, (5) Department of Earth Science, Natural History Museum, London, UK, (6) Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274 CNRS, France, (7) Institute of Planetary Research, DLR, Belin, Germany, (8) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA, (9) Physikalisches Institut, University of Bern, Switzerland, (10) Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA, (11) Centre for Planetary Science and Exploration/ Department of Earth Sciences, University of Western Ontario, London, Canada CaSSIS image Summary CAS-M01-2018-05-06T12.52.27.314 A Geologic context Filters RED, PAN, BLU in RGB colours The CaSSIS colour stereo camera of ExoMars/TGO views the surface Large volumes of sediments were deposited in the Ladon basin during late and of Mars with 4 filters in the range 0.4-1.2 µm and pixel size 4.6 m. Its [2], transported from the surrounding Noachian terrains through a vast and colour capabilities for geological interpretations are explored in the multiphase drainage system. Groundwater flow is thought to play an important role in the evolution of the region, in connection with the formation of the several nearby chaos. The Ladon impact basin, where it reveals unexpected geology, that basin undergone later widespread extensional fracturing and more sparsely, contractional CRISM, CTX, and HiRISE data help interpret further. Most likely, the deformation [3]. Some of the fractures are radial or concentric about filled craters, others are consistently NNW-dipping. surface is capped by a thin mafic or ultramafic flow, dated early or middle , underlain by a serpentinised flow. These results 1 Measured transmission curves indicate that a long time after formation, the Ladon basin had AURORAE CHAOS through the centres of each of the bandpass filters [1] undergoing volcanic and hydrothermal activity, and reveals the exceptional potential of CaSSIS for geologic mapping.

CaSSIS image footprint Evidence of intraformational alteration LADON BASIN 2

Unit 4 C Unit 3 N 3 500 m Numbers refer to units MOLA context of the Ladon basin and the studied CaSSIS image. in the geologic cross HiRISE image ESP_013045_1615 section

4 Unit 1

CaSSIS One of the first CaSSIS images Unit 4 CRISM captured an area in Ladon HiRISE showing one such fracture or graben. This site was targeted Unit 3 CTX DTM so as to test the spectral capabilities of the 4 filters of Unit 2 CaSSIS, in the blue-green (BLU), a broad red (PAN), and CaSSIS image draped over CTX DTM generated by fusion of photogrammetric and photoclinometric two near-infrared (RED, NIR) information [6], of vertical resolution 1 m. [A], and to benefit from existing CRISM, CTX, and HiRISE data covering the area. -2020 E W This CaSSIS image was acquired as a non-stereo -2030 Topography individual acquisition, but a 0 1 2 3 After [3]. Units HNb2 and Hb3 are interpreted as sedimentary basin fill units of ageLate CTX digital elevation model -2040 Noachian-Late Hesperian, HNt are smooth to rolling, cratered, and variably dissected surfaces (DTM) is available. km between degraded impact craters (AHc2). -2050

-2060 Unit 3 B New ages D Rock composition (m) height -2070 -2080

-2090 Unit 1 (HNb2) Unit 4 Units 1-4 Serpentine in Unit 3 -2100 Unit 4 X:289 Y:355 Representative CRISM spectra may not be reliable Unit 4 X:364 Y:436 -2110 Unit 4 X:248 Y:348 0 500 1000 1500 2000 2500 3000 Unit 4 X:263 Y:380 RA-REA-018 serpentinite (Egypt) distance along cliff (m) <45μm (Relab)

Unit 2 X:532 Y:461

Unit 1 X:531 Y:88

Unit 2 X:155 Y:126 CRISM serpentine Olivine and Conclusion (Claritas Rise, CRISM Library) pyroxene in units 1-2 Unit 1 X:296 Y:90 Unit 2 (Hb3) New dating of the local units indicates Averaged dune field (3969 pixels) We illustrate the usefulness of CaSSIS imagery to Unit 3 X:338 Y:210 that lava outpouring occurred later than unify earlier datasets in a coherent geological Unit 3 X:272 Y:265 1.05 2.18 expected (see A), during early or middle framework. Amazonian. Unit 2 X155 Y126 Unit 3 X:176 Y:371 Unit 3 X:176 Y:372 2.18 1. The layers studied here have been interpreted as sedimentary deposits, such as aqueous sediments, Unit 1 X296 Y90 evaporites, or duricrust [3]. Unit 1 is spectrally close to Mg-olivine 2.18 (forsterite), with absorptions also Unit 3 X:176 Y:371 2. The CaSSIS image allows to follow the light-toned suggesting the presence of pyroxenes Unit 3 X:176 Y:372 serpentine diagnostic bands [4] Augite 2.26 layers for a longer distance than on HiRISE imagery, of pigeonite-augite composition. Unit NMNH120049 2 is spectrally similar to Unit 1. Unit 3 making possible new interpretation. has the diagnostic absorption features 3. High-resolution DTM shows that these layers Units 3-4 of serpentine [4] in the range 1.0-2.6 Unit 1 Olivine, iron and chromite 2.08 µm. Olivine associated with a small Unit 1 in Unit 3 Pigeonite have variable thicknesses over very short distances, amount of chromite (5%, [5]) well Unit 2 HS199.3B suggesting that they are alteration layers. matches spectra in the range 0.4-1.4 µm. Clinochlore and minerals of Unit 3 4. CRISM cube analysis suggests that the yellow hydrothermal origin have also been layer probably includes serpentine. identified. The mineralogy of Unit 4 is weakly defined. In addition, a HiRISE Unit 4 5. Furthermore, CRISM data also indicates that the image suggests the presence of rare MX-EAC-028 1.05 rocks exposed at the surface are of either mafic or chloride deposits, from comparison Unit 2 Olivine 67.5% OLV003 with documented chloride deposits Iron powder 22.5% MET101 Olivine (Fo88%) ultramafic composition. X:289 Y: 335 Chromite 10% on Mars. CHR103 45-90 µm FRT000128EA_07_IF164J_MTR3 6. It follows that the simplest scenario for bands 304-122-41 explaining the geology of this area is serpentinite alteration of ultramafic lava outpourings during Amazonian. The groundwater table documented Capping mafic or ultramafic flow E NNW Unit 1 Geologic cross section SSE until the mid-Hesperian [2] may have persisted Underlying flows and other rocks elevation (m) Unit 2 during the Amazonian and be involved in these layering processes. -2000 SLOPE 1° ? References -2100 ? Chloride lexure Unit 3 Serpentinite, with dyke intrusion fault f water table [1] Thomas, N., et al., 2017, Space Sci. Rev. 10.1007/s11214-017-0421-1 Unit 4 White alteration layer [2] Grant, J.A., and Parker T.J., 2002, J. Geophys Res. 107(E9), 5066 2000 m [3] Irwin, R.P., III., and Grant, J.A., 2013, USGS Scientific Investigation Map 3209 Dunes on fracture filling material [4] Ehlmann, B.L., et al., 2009, J. Geophys Res. 114, E00D08 [5] Cloutis, E.A., Sunshine, J.M., and Morris, R.V., 2004, Meteor. Planet. Sci. 39, 545–565 [6] Jiang et al., 2017, ISPRS 2017, 130, 418–430 ex MHYDR