Crust stratigraphy and heterogeneities of the first kilometers at the dichotomy boundary in western Elysium Planitia and implications for InSight lander L. Pan, C. Quantin-Nataf, B. Tauzin, C. Michaut, M. Golombek, P. Lognonné, P. Grindrod, Benoit Langlais, T. Gudkova, I. Stepanova, et al. To cite this version: L. Pan, C. Quantin-Nataf, B. Tauzin, C. Michaut, M. Golombek, et al.. Crust stratigraphy and heterogeneities of the first kilometers at the dichotomy boundary in western Elysium Planitia and implications for InSight lander. Icarus, Elsevier, 2020, 338, pp.113511. 10.1016/j.icarus.2019.113511. hal-02346218 HAL Id: hal-02346218 https://hal.archives-ouvertes.fr/hal-02346218 Submitted on 7 Aug 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution - NonCommercial| 4.0 International License Icarus 338 (2020) 113511 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus Crust stratigraphy and heterogeneities of the first kilometers at the dichotomy boundary in western Elysium Planitia and implications for InSight lander Lu Pan a,*, Cathy Quantin-Nataf a, Benoit Tauzin a,b, Chlo�e Michaut c, Matt Golombek d, LognonnePhillipe Lognonn�e e, Peter Grindrod f, Benoit Langlais g, Tamara Gudkova h, Inna Stepanova h, S�ebastien Rodriguez e, Antoine Lucas e a Universit�e de Lyon, Universit�e Claude Bernard Lyon 1, ENS de Lyon, CNRS, UMR 5276 Laboratoire de G�eologie de Lyon -Terre, Plan�etes, Environnement, 69622 Villeurbanne, France b Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia c Universit�e de Lyon, Ecole� Normale Sup�erieure de Lyon, UCBL, CNRS, Laboratoire de G�eologie de Lyon -Terre, Plan�etes, Environnement, 69007 Lyon, France d Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States of America e Universit�e de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France f The Natural History Museum at Tring Akeman Street, Tring, Hertfordshire HP23 6AP, United Kingdom of Great Britain and Northern Ireland g Laboratoire de Plan�etologie et G�eodynamique, Univ. Nantes, Univ. Angers, CNRS, UMR 6112, F-44000 Nantes, France h Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya 10, Moscow 123495, Russia ARTICLE INFO ABSTRACT Keywords: InSight landed on Mars on November 26, 2018, in western Elysium Planitia. The Mars crust beneath the lander is Mars subject to complex geologic history next to the great topographic and crustal dichotomy of Mars. Understanding Cratering this part of the Martian crust in the subsurface would aid future investigations of the internal structure of the Geological processes planet based on seismic datasets collected by the Seismic Experiment for Interior Structure (SEIS) instrument. Mineralogy Here, we investigate the subsurface structure and composition from the analysis of mineralogy and morphology Spectroscopy of exposures in impact craters as well as on scarps and knobs in the general region of Elysium Planitia. Using a combination of orbital datasets, we identify exposures of subsurface materials with distinct composition and physical properties. We findolivine and pyroxene detections associated with small impact craters (1.5–7 km) rim in the vicinity of InSight lander, as well as in the transition unit and Elysium volcanic unit. Fe/Mg phyllosilicates have been identified in the central peak of the 51-km diameter Kalpin crater and on knobs in the transition unit between the dichotomy and the plains. In addition, eroded meter-scale layered unit subject to erosion has been identifiedin six impact craters to the north-east of the landing site, including Kalpin crater. Massive bedrock and layered, weak materials co-occur in the transition unit, indicating a complex origin. These results together suggest both materials with altered composition and layered deposit occur as distinct geologic units beneath the basaltic lava flow units. Through analogy with terrestrial sedimentary rocks or clay-bearing sediments, we suggest physically weak materials exist beneath the lava flowunits in the general region of Elysium Planitia. The spatial distribution and continuity of these materials are unclear due to the lack of exposures within the lava flow unit where the InSight lander is located. These subsurface materials of distinct physical properties may result in increased attenuation or reverberations of seismic waves, to be collected by SEIS. The findings suggest a close investigation of the potential effects of subsurface stratigraphy on seismic data would help inform future data interpretation and understanding of the internal structure of Mars. * Corresponding author at: 2 rue Rapha€el Dubois, Batiment^ GEODE, Villeurbanne 69622, France. E-mail address: [email protected] (L. Pan). https://doi.org/10.1016/j.icarus.2019.113511 Received 20 May 2019; Received in revised form 16 September 2019; Accepted 26 October 2019 Available online 31 October 2019 0019-1035/© 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). L. Pan et al. Icarus 338 (2020) 113511 1. Introduction 2013, 2017) and successfully landed on November 26, 2018. The InSight lander explores the interior of Mars with a set of geophysical instruments The Martian crust has been probed using the global scale topography (e.g. Banerdt et al., 2017), including the Seismic Experiment for Interior and gravity returned from Mars Global Surveyor mission (Smith et al., Structure (SEIS) (Lognonne� et al., 2019), the Rotation and Interior 1999; Zuber et al., 2000), however, the internal 3D structure of Mars (e. Structure Experiment (RISE) (Folkner et al., 2018), and the Heat Flow g. core size, crustal thickness) still has large uncertainties. To better and Physical Properties Package (HP3) (Spohn et al., 2018). One of the understand the formation and evolution of the terrestrial planets, the main science goals of the InSight mission is to understand the internal InSight (Interior Exploration using Seismic Investigations, Geodesy and structure of Mars from seismic activity. The SEIS instrument is the first Heat Transport) robotic lander launched on May 5, 2018 as the first seismometer placed on Mars’ surface and it consists of a 3-axis very mission to investigate the interior structure of Mars (Banerdt et al., broad band (VBB) instrument and a 3-axis short period (SP) instrument. Fig. 1. Geologic context of InSight landing site: A) The location of InSight landing ellipse in the southwest flank of Elysium Mons volcanic terrains, north of the dichotomy boundary. Upper left corner shows a Mars globe with the highlighted region of map and landing site location. The base map is Mars THEMIS daytime infrared mosaic overlain by the topography from Mars Orbiter Laser Altimeter (MOLA), in Mars equirectangular projection. B). Geological map with the same map extent (Tanaka et al., 2014) showing the major geologic units and structures in the region. Geological unit abbreviations follow the USGS global map. Nhe: Noachian Hesperian unit; HNt: Hesperian and Noachian transition unit; eHt: Early Hesperian transition unit; lHt: late Hesperian transition unit; lHl: late Hesperian unit; Hve: Hesperian volcanic unit; AHv: Amazonian-Hesperian volcanic unit; lAv: late Amazonian volcanic unit; lHvf: Late Hesperian volcanic fieldunit; AHi: Amazonian and Hesperian Impact unit; Htu: Hesperian transition undivided unit; AHtu: Amazonian and Hesperian transition undivided unit. C) Gridded free-air gravity model (MRO120D (Konopliv et al., 2016)) for the landing site region with spherical harmonic degrees from 7 to 90 overlain on the MOLA hill shade. D) Magnetic field intensity map of the landing site region overlain on MOLA hill shade map following Langlais et al. (2019). 2 L. Pan et al. Icarus 338 (2020) 113511 The finallanding site for InSight lander (the E9 ellipse) is located in instrument onboard the InSight lander based on the information of the western Elysium Planitia near the dichotomy boundary, south of geologic structure of the landing site region. We propose six crustal Elysium Mons shield volcano, in particular to satisfy the constraints on models for future modeling effort and seismic data analysis based on landing safety and the instrument deployment requirements (Golombek these geological constraints that we provide as supplementary material. et al., 2017). Within the northern lowlands (Fig. 1), the landing ellipse is located on the flat, rocky lava plains mapped as Hesperian aged unit 2. Geological and geophysical background of the landing site (eHt) (Tanaka et al., 2014). As the 4–6 km topographical difference region between the northern lowlands and southern highlands formed very early (Frey et al., 2002), the dichotomy boundary has been subjected to Situated between the Elysium volcanic structure and the dichotomy degradation and accumulation of sediments