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Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin

Scheller, Eva L. and Ehlmann, Bethany L. (2020) Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin. Journal of Geophysical Research. Planets, 125 (7). Art. No. e2019JE006190. ISSN 2169-9097.

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The western part of the Isidis basin structure hosts a well‐characterized Early Noachian to Amazonian stratigraphy. The Noachian Basement comprises its oldest exposed rocks (Early to Mid‐Noachian) and was previously considered a single low‐Ca pyroxenes (LCP)‐ and Fe/Mg‐smectite‐bearing unit. Here, we divide the Noachian Basement Group into five distinct geological units (Stratified Basement Unit, Blue Fractured Unit, Mixed Lithology Plains Unit, LCP‐bearing Plateaus Unit, and Fe/Mg‐smectite‐bearing Mounds Unit), two geomorphological features (megabreccia and ridges), and a mineral deposit (kaolinite‐bearing bright materials), based on geomorphology, spectral characteristics, and stratigraphic relationships. Megabreccia contain four different pre‐Isidis lithologies, possibly including deeper crust or mantle materials, formed through mass wasting associated with transient crater collapse during Isidis basin formation. The Fe/Mg‐smectite‐bearing Stratified Basement Unit and LCP‐bearing Blue Fractured Unit likewise represent pre‐Isidis units within the Noachian Basement Group. Multiple Fe/Mg‐smectite‐bearing geological units with different stratigraphic positions and younger kaolinite‐bearing bright materials indicate several aqueous alteration episodes of different ages and styles. Units with slight changes in pyroxene spectral properties suggest a transition from low‐Ca pyroxene‐containing materials to those with higher proportions of pyroxenes higher in Ca and/or glass that could be related to different impact and/or igneous processes, or provenance. This long history of Noachian and potentially Pre‐Noachian geological processes, including impact basin formation, aqueous alteration, and multiple igneous and sedimentary petrogeneses, records changing ancient Mars environmental conditions. All units defined by this study are available 20 km outside of Jezero crater for in situ analysis and sampling during a potential extended mission scenario for the Mars 2020 rover.

Item Type:Article
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Scheller, Eva L.0000-0002-9981-5802
Ehlmann, Bethany L.0000-0002-2745-3240
Additional Information:© 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Received 3 SEP 2019; Accepted 11 FEB 2020; Accepted article online 10 MAR 2020. We would like to thank the NASA Earth and Space Science Fellowship (NESSF) (Grant 80NSSC18K1255) for supporting this project. This work was made possible by data produced and made available through the immense efforts of the CRISM, HiRISE, and MOLA teams. These data sets can be accessed through the Planetary Data System (PDS) archives, maintained by NASA. Tables of megabreccia attributes, block sizes, and orientation measurements from this study can be found in the supporting information and on the Caltech Research Data Repository ( Special acknowledgements are owed to Jay Dickson and the Murray Lab for guiding development of data analysis procedures and providing data products such as HiRISE DEMs and CTX mosaic. Additionally, we would like to thank Lu Pan and Daven Quinn for assistance and development of data analysis software used in this study. This work benefited from the invaluable discussion provided by Ben Weiss, Peter Schultz, Alex Trowbridge, Jay Melosh, Horton Newsom, Gordon Osinski, Jeffrey Plescia, Briony Horgan, Nina Lanza, Paul Asimow, Zach Gallegos, and other Mars 2020 Science Team members. We would also like to thank our reviewers, Katie Stack and Christina Viviano, as well as our editor, Deanne Rogers, for their suggestions that have led to the improvement of this paper.
Group:Astronomy Department
Funding AgencyGrant Number
NASA Earth and Space Science Fellowship80NSSC18K1255
Subject Keywords:Mars; Mars‐2020; Noachian; Nili Fossae; Impacts; Megabreccia
Issue or Number:7
Record Number:CaltechAUTHORS:20200408-131502595
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Official Citation:Scheller, E. L., & Ehlmann, B. L. (2020). Composition, Stratigraphy, and Geological History of the Noachian Basement Surrounding the Isidis Impact Basin. Journal of Geophysical Research: Planets, 125, e2019JE006190.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102403
Deposited By: Tony Diaz
Deposited On:08 Apr 2020 20:47
Last Modified:17 Mar 2021 17:09

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