| Title: |
Stratigraphy of Carbonate‐Bearing Rocks at the Margin of Jezero Crater, Mars: Evidence for Shoreline Processes? |
| Authors: |
Jones, Alexander J.1 (AUTHOR) alexander.jones19@imperial.ac.uk; Gupta, Sanjeev1 (AUTHOR); Barnes, Robert1 (AUTHOR); Horgan, Briony H. N.2 (AUTHOR); Williford, Kenneth H.3 (AUTHOR); Paar, Gerhard4 (AUTHOR); Stack, Kathryn. M.5 (AUTHOR); Garzcynski, Bradley J.6 (AUTHOR); Ravanis, Eleni7 (AUTHOR); Bedford, Candice C.2 (AUTHOR); Simon, Justin I.8 (AUTHOR); Klidaras, Athanasios2 (AUTHOR); Kah, Linda C.9 (AUTHOR); Bell, James F.10 (AUTHOR); Maki, Justin5 (AUTHOR); Lokier, Stephen W.11 (AUTHOR); Brown, Adrian12 (AUTHOR); Williams, Nathan R.5 (AUTHOR); Alwmark, Sanna13 (AUTHOR); Núñez, Jorge I.14 (AUTHOR) |
| Source: |
Journal of Geophysical Research. Planets. Jan2026, Vol. 131 Issue 1, p1-48. 48p. |
| Subject Terms: |
*Hydrology; Carbonate rocks; Shorelines; Cratering; Martian exploration; Mars rovers; Biostratigraphy |
| Company/Entity: |
United States. National Aeronautics & Space Administration |
| Abstract: |
Martian carbonate‐bearing rocks are compelling targets for exploration because they preserve detailed records of past aqueous processes, climate, and habitability. The Margin unit in Jezero crater is a distinct olivine‐ and carbonate‐bearing unit stratigraphically underlying the western fan, lining the inner margin of the western crater rim and has a contested origin. Perseverance spent ∼350 sols investigating the unit as part of its fourth mission campaign, aiming to constrain its origin, alteration history and biosignature preservation potential. This study reports on the lithofacies and stratigraphy of the unit by analyzing Mastcam‐Z mosaics and derived 3D outcrop models, supplemented by long‐distance SuperCam observations and detailed textural analyses from SHERLOC WATSON and ACI images. We find that the Margin unit comprises two distinct sub‐units. The Eastern Margin Unit (EMU) comprises well‐stratified, low‐angle basinward‐, rimward‐ and sub‐horizontally inclined medium‐grained sandstones which preserve angular to rounded grains, occasional cross‐stratification, convex‐up bedding, and erosion surfaces. The Western Margin Unit (WMU) comprises distinctly structureless to decimeter‐scale parallel‐layered rocks which drape the crater rim and are inclined into the crater. The origin of the WMU is uncertain but may be most consistent with a variably carbonated olivine cumulate. The favored depositional model for the EMU is a lacustrine shore zone environment where sediments derived from the adjacent WMU have been locally reworked by wave action along a paleoshoreline at around –2,400 m elevation. These observations suggest that the Margin unit preserves diverse subsurface and surface aqueous environments and further extends the habitability window at Jezero crater. Plain Language Summary: Carbonate minerals are rare on Mars and are important targets because they preserve information about ancient climates, water availability, and habitable environments. NASA's Mars 2020 Perseverance rover spent around one Earth year exploring the "Margin unit", a geologic unit lining the inner crater rim west of the Jezero delta, rich in olivine and carbonate‐minerals. Here, we use images acquired by Perseverance to describe the Margin unit rocks and consider how they formed. The Margin unit primarily consists of structureless to thick‐layered rocks with compositions and textures suggesting they have experienced significant alteration by subsurface circulating water. This alteration makes determining their origin challenging, but their overall structure, texture, composition and distribution appear most consistent with an igneous origin, formed by crystal settling in a cooling body of molten rock. At lower elevations in the east, the Margin unit displays rounded grains and sedimentary structures consistent with a lake shore environment. These rocks are interpreted as a sandy veneer reworked from the bulk of the Margin unit by waves at the Jezero lake shoreline. These observations show that the Margin unit preserves multiple ancient, and potentially habitable, settings, including water‐rich surface and subsurface environments. Key Points: The Margin unit underlies the Jezero Western fan, drapes the inner crater rim and may record both igneous and sedimentary lithofaciesMost of the unit comprises structureless to planar‐layered rocks, which most likely preserve an aqueously altered olivine cumulateIn the east of the unit, rounded grains and sedimentary structures indicate reworking by waves along the shoreline of the Jezero paleolake [ABSTRACT FROM AUTHOR] |
| : |
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) |
| Database: |
GreenFILE |