Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial‐Lacustrine Activity From Orbital Observations

Abstract

On February 18, 2021 NASA s Perseverance rover landed in Jezero crater, located at the northwestern edge of the Isidis basin on Mars. The uppermost surface of the present-day crater floor is dominated by a distinct geologic assemblage previously referred to as the dark-toned floor. It consists of a smooth, dark-toned unit overlying and variably covering light-toned, roughly eroded deposits showing evidence of discrete layers. In this study, we investigated the stratigraphic relations between materials that comprise this assemblage, the main western delta deposit, as well as isolated mesas located east of the main delta body that potentially represent delta remnants. A more detailed classification and differentiation of crater floor units in Jezero and determination of their relative ages is vital for the understanding of the geologic evolution of the crater system, and determination of the potential timeline and environments of habitability. We have investigated unit contacts using topographic profiles and DEMs as well as the distribution of small craters and fractures on the youngest portions of the crater floor. Our results indicate that at least some of the deltaic deposition in Jezero postdates emplacement of the uppermost surface of the crater floor assemblage. The inferred age of the floor assemblage can therefore help to constrain the timing of the Jezero fluviolacustrine system, wherein at least some lake activity postdates the age of the uppermost crater floor. We present hypotheses that can be tested by Perseverance and can be used to advance our knowledge of the geologic evolution of the area. Plain Language Summary On February 18, 2021 NASA s Perseverance rover landed in Jezero crater on Mars. In the past, the crater was filled with water, forming a lake, and in the western part of the crater an ancient delta is preserved. Part of the present-day crater floor has been interpreted to represent a lava flow that was deposited after the lake dried out, meaning that the floor unit would be younger than the western delta. In order to understand how the Jezero crater lake has developed over time, including the potential timeline and environments of habitability, it is necessary to work out the relations between the geologic units in Jezero crater. In this work, we have analyzed orbital images of Jezero crater and reveal how the crater floor and delta deposits relate to each other in time. Our results show that at least some of the deltaic deposits in Jezero overlie the youngest crater floor unit(s). It is therefore possible to learn broadly when fluvial activity in the crater has been effective from the age of the crater floor. Our work presents hypotheses that can be tested by Perseverance to advance our knowledge of how the area has evolved geologically over time. HOLM-ALWMARK ET AL. © 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Stratigraphic Relationships in Jezero Crater, Mars: Constraints on the Timing of Fluvial-Lacustrine Activity From Orbital Observations S. Holm-Alwmark , K. M. Kinch , M. D. Hansen, S. Shahrzad, K. Svennevig , W. J. Abbey, R. B. Anderson , F. J. Calef III , S. Gupta, E. Hauber , B. H. N. Horgan , L. C. Kah , J. Knade, N. B. Miklusicak, K. M. Stack, V. Z. Sun , J. D. Tarnas, and C. Quantin-Nataf Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark, Natural History Museum Denmark, University of Copenhagen, Copenhagen, Denmark, Department of Geology, Lund University, Lund, Sweden, School of Earth and Environment, University of Leeds, Leeds, UK, Geological Survey of Denmark and Greenland, Copenhagen, Denmark, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, U.S. Geological Survey, Astrogeology Center, Flagstaff, AZ, USA, Department of Earth Science and Engineering, Imperial College London, London, UK, German Aerospace Center, Institute of Planetary Research, Berlin, Germany, Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA, Department of Earth and Planetary Sciences, University of Tennessee-Knoxville, Knoxville, TN, USA, Laboratoire de Géologie de Lyon -Terre, Planètes, Environnement, University of Lyon, Lyon, France Key Points: • We have studied stratigraphic relations between geologic units in Jezero crater for determination of relative age relations in the crater • Topographic profiles and digital elevation models indicate that the western delta is on top of the youngest crater floor unit(s) • We thus place constraints on the timeline of fluvial-lacustrine activity in Jezero crater