AbstractThe ROMA database (ROck reflectance for MArtian in situ exploration, https://roma.univ-lyon1.fr) provides the reflectance spectra between 0.4 and 3–4 μm of various terrestrial, Martian, and synthetic samples, as a means to document reference measurements for comparison with data acquired by visible and near‐infrared spectrometers on planetary surfaces, with a focus on current and future Martian observations by the Perseverance (Mars 2020 mission) and Rosalind Franklin (ExoMars) rovers. The main specificity of this database is to include a significant fraction of spectra of unprocessed rock, which are more realistic analogs and often have different spectral features than the fine powders more commonly analyzed in reflectance spectroscopy. Additionally, these measurements were acquired with a spectrometer whose spot size is similar to those of the SuperCam instrument (Mars 2020 mission) at a few meters from a target. Supplementary information are provided in the ROMA database: higher‐level data (such as absorption band parameters) as well as sample mineralogy estimated by whole‐rock X‐ray diffraction analyses. Future comparisons with this database will help improve the interpretation of spectral measurements acquired on the Martian surface. This work introduces the aim of the library and its current state, but additional data on intact natural rock surfaces will likely be added in the future.

ABSTRACT The most recent comprehensive database of Martian impact craters was the result of the work of impact crater scientists (S.J. Robbins and B.M. Hynek) who carefully examined the available high-resolution imagery of Mars. Building on this previous work, we present the result of an alternative approach involving 56 planetary scientists and trained students. A web platform was designed for this purpose. All impact craters larger than 1 km in diameter were classified according to a simplified classification scheme, recording the primary or secondary nature of the crater, and the morphology of the ejecta (single, double, or multiple layered ejecta rampart sinuous [LERS], or low-aspect-ratio layer ejecta [LARLE]). In total, 8445 LERS craters, 24,530 partially buried craters, 55,309 secondary craters, and 288,155 craters in the category “standard” were identified. Our assessment differs for 8145 entries in the original database compiled by Robbins and Hynek, which are not considered to be impact structures. In this work, ~39,000 secondary craters have been associated with 108 primary craters. Coupled to the existing database, the database we propose here offers a complementary way to investigate the geological history of Mars. More specifically, the completion of layered ejecta crater morphologies down to 1 km and the connection established between secondary and primary impact crater sources will allow the implementation of statistical studies to reveal the spatial and temporal evolution of the impacted material characteristics. Thanks to the simplified classification we performed here, this version of the database can be easily used as a training data set for crater identification algorithms based on machine-learning techniques with the aim to identify smaller impact craters and to automatically define their morphological characteristics. Since it is not possible to confirm an impact structure from remote-sensing data alone, any Martian impact database at this stage remains subjective, and its assessment must be facilitated. The interface we developed for this participative project can be directly used for this purpose and for continuous updates and improvements of this work, in particular, with the latest high-resolution imagery releases such as the CTX global mosaic by J.L. Dickson and others, but also as a platform for building specific databases of craters or any other structures located in a particular region of interest.

This volume represents the proceedings of the homonymous international conference on all aspects of impact cratering and planetary science, which was held in October 2019 in Brasília, Brazil. The volume contains a sizable suite of contributions dealing with regional impact records (Australia, Sweden), impact craters and impactites, early Archean impacts and geophysical characteristics of impact structures, shock metamorphic investigations, post-impact hydrothermalism, and structural geology and morphometry of impact structures—on Earth and Mars. Many contributions report results from state-of-the-art investigations, for example, several that are based on electron backscatter diffraction studies, and deal with new potential chronometers and shock barometers (e.g., apatite). Established impact cratering workers and newcomers to the field will appreciate this multifaceted, multidisciplinary collection of impact cratering studies.

The Nili Fossae region of Mars exhibits from remote sensing spectral data the largest exposures of olivine-rich materials on the planet. However, it is not clearly constrained how and when these terrains formed. Some of the proposed scenarios favor a mode of formation closely related to Isidis impact basin: either under intense effusive volcanism following the impact, from cooling of an immediate impact melt sheet or silicate impact vapor condensate. These deposits might also be pyroclastic products ejected from now eroded or buried vents. Recent studies also proposed that lag deposits could be responsible for enrichment in olivine after deposition. In this contribution, we mapped the olivine-rich unaltered and altered bedrock exposures using near infrared and thermal inertia data, investigated the geometry and key contacts of the olivine-rich unit, and determined its surface age using crater counts and stratigraphical relationships. We find that the olivine-rich bedrock extends over at least similar to 18,000 km(2) in the Nili Fossae region, with a large part of it being unaltered. Olivine-rich material that overlaps the northern rim of Jezero crater corresponds to a primary deposit (i.e. rather than reworked material). Since this crater is younger than Isidis, we favor the hypothesis of a post-Isidis origin, rather than the impact melt (consistently with Bramble et al., 2017) and impact condensate origin. Based on our observations and crater counts, we estimate an emplacement age of 3.82 +/- 0.07 Ga (Mid to Late Noachian). We discuss the origin of the unit, with the most likely scenarios being ash falls and/or pyroclastic surges. To explain the circumIsidis distribution of these deposits, we favor the hypothesis of a thinned and weakened crust in the region subsequently to the giant impact of Isidis, as suggested by Tornabene et al. (2008). Finally, the distribution of altered bedrock conflicts with the contact metamorphism scenario. As the olivine-rich unit exposed at Jezero crater, future home of the Mars 2020 rover, is a regional stratigraphic marker, return samples for precise dating of this unit should be made one of the major mission targets.

MarsSI (Acronym for Mars System of Information, https://emars.univ-lyonl.fr/MarsSI/) is a web Geographic Information System application which helps managing and processing martian orbital data. The MarsSI facility is part of the web portal called PSUP (Planetary SUrface Portal) developed by the Observatories of Paris Sud (OSUPS) and Lyon (OSUL) to provide users with efficient and easy access to data products dedicated to the martian surface. The portal proposes 1) the management and processing of data thanks to MarsSI and 2) the visualization and merging of high level (imagery, spectral, and topographic) products and catalogs via a web-based user interface (MarsVisu). The portal PSUP as well as the facility MarsVisu is detailed in a companion paper (Poulet et al., 2018). The purpose of this paper is to describe the facility MarsSI. From this application, users are able to easily and rapidly select observations, process raw data via automatic pipelines, and get back final products which can be visualized under Geographic Information Systems. Moreover, MarsSI also contains an automatic stereo-restitution pipeline in order to produce Digital Terrain Models (DTM) on demand from HiRISE (High Resolution Imaging Science Experiment) or CTX (Context Camera) pair-images. This application is funded by the European Union's Seventh Framework Programme (FP7/2007-2013) (ERC project eMars, No. 280168) and has been developed in the scope of Mars, but the design is applicable to any other planetary body of the solar system.

Pedogenesis has been previously proposed on the plateaus around Coprates Chasma, Valles Marineris to explain the presence of widespread clay sequences with Al-clays and possible hydrated silica over Fe/Mg-clays on the surface of the plateaus (Le Deit et al., 2012; Carter et al., 2015). We use previous observations together with new MRO targeted observations and DEMs to constrain the extent and thickness of the plateau clay unit: the Al-clay unit is less than 3 m thick, likely similar to 1 m, while the Fe/Mg-clays underneath are few tens of meters thick. We also refine the age of alteration by retrieving crater retention ages of the altered plateau and of later deposits: the observed clay sequence was created by surface pedogenesis between model ages of 4.1 Ga and 3.75 Ga. Using a leaching model from Zolotov and Mironenko (2016), we estimate the quantity of atmospheric precipitations needed to create such a clay sequence, that strongly depends on the chemistry of the precipitating fluid. A few hundreds of meters of cumulated precipitations of highly acidic fluids could explain the observed clay sequence, consistent with estimates based on late Noachian valley erosion for example (Rosenberg and Head, 2015). We show finally that the maximum quantity of sulfates potentially formed during this surface weathering event can only contribute minimally to the volume of sulfates deposited in Valles Marineris. (C) 2017 Elsevier Inc. All rights reserved.

THE REGION OF NILI FOSSAE, MARS. L. Mandon1, C. Quantin1, P. Thollot1, L. Lozac’h1, N. Mangold2, G. Dromart1, P. Beck3, E. Dehouck1, S. Breton1, C. Millot1. 1 Laboratoire de Géologie de Lyon Terre, Planètes, Environnement, Université de Lyon, France. 2 Laboratoire de Planétologie et Géodynamique, Université de Nantes, France. 3 Institut de Planétologie et d'Astrophysique de Grenoble, Université Grenoble Alpes, France. lucia.mandon@univ-lyon1.fr.

EXOMARS LANDING SITE OXIA PLANUM. S. Rossato, M. Pajola, E. Baratti, R. Pozzobon, C. Quantin, J. Carter, P. Thollot, Department of Geosciences, University of Padova, Via G. Gradenigo, 6 35131 Padova, Italy sandro.rossato@unipd.it riccardo.pozzobon@oapd.inaf.it, NASA Ames Research Center, Moffett Field, CA 94035, USA maurizio.pajola@nasa.gov, School of Civil Engineering, Department DICAM, University of Bologna, Bologna, Italy emanuele.baratti@unibo.it, Laboratoire de Géologie de Lyon Terre, Planètes, Environnement (CNRS-ENS Lyon-Université), Lyon1, France cathy.quantin-nataf@univ-lyon1.fr patrick.thollot@ens-lyon.fr, Institut d'Astrophysique Spatial, Université Paris 11-Orsay, France john.carter@ias.u-psud.fr.

Introduction: A large diversity of hydrated minerals has been observed on Mars from orbit thanks to spectral imagers like OMEGA/Mars Express and CRISM/MRO [1, 2, 3]. These hydrated minerals are observed in different geologic contexts and in terrains of various ages. Of particular interest are the hydrated minerals formed originally at the surface: they inform us that liquid water was repetedly present or stable at the surface of Mars when they formed. In particular, similar sequences of clay minerals have been observed in several regions of the planet, in different regional contexts. These sequences have however all been identified in terrains dating from the early Hesperian or earlier. These clay sequences show Fe/Mg smectite-bearing rocks overlain by Al phyllosilicate bearing rocks. On Earth, such a mineralogic sequence is formed by pedogenic top-down leaching: the closer to the surface, the higher the rocks are leached, removing Mg and Fe cations. Places where such a clay sequence is observed on Mars are therefore a clue that sufficient precipitation happened at those places to weather rocks from the surface to tens of meters of depth [4]. One region where these clay sequence has been observed is located in the eastern end of Valles Marineris, on both sides of Coprates Chasma [5]. The present study focuses on the outcrops of this sequence which are exposed on the plateau south of Coprates, where early results showed the most extended occurences. The exact extent of this clay sequence is mapped. This will help in constraining the age of the weathering and the thickness of the clay sequence, in order to evaluate the time and intensity of the aqueous weathering in this region.

Introduction: Geological investigations of planetary surfaces are based on the exploitation of orbital data and often acquired with different remote sensing instruments. For Mars, for instance, the number of missions and instruments and the size of the datasets are so important that even at the scale of a single scientific team, an information system to manage data is more and more required. The creation and exploitation of a database of Mars surface is part of the e-Mars project funded by the European Research Council (ERC), the aim of which is to decipher the geological evolution of the planet from the combination of Martian orbital data. We have designed a distributed information system called MarsSI to manage data from the four following Martian orbiters: Mars Global Surveyor (MGS), Mars Odyssey (ODY), Mars Express (MEX), and Mars Reconnaissance Orbiter (MRO). MarsSI allows the user to select footprints of the data from a web-GIS interface and download them to a storage server. Then the user can process raw data via automatic calibrations and finally acquire “ready-to-use” data of Mars surface. “Readyto-use” means that the data are ready to be visualized under Geographic Information System (GIS) or remote sensing softwares. An automatic stereo-restitution pipeline producing high resolution Digital Terrain Models (DTM) is also available.