| Title: |
A Fluvio‐Lacustrine Environment Preserved in the Jezero Crater Inlet Channel, Neretva Vallis, Mars. |
| Authors: |
Jones, Alexander J.1 (AUTHOR) alexander.jones19@imperial.ac.uk; Barnes, Robert1 (AUTHOR); Gupta, Sanjeev1 (AUTHOR); Paar, Gerhard2 (AUTHOR); Hurowitz, Joel3 (AUTHOR); Wogsland, Brittan V.4 (AUTHOR); Broz, Adrian5 (AUTHOR); Kalucha, Hemani6 (AUTHOR); Klidaras, Athanasios5 (AUTHOR); Stack, Kathryn M.7 (AUTHOR); Russell, Patrick8 (AUTHOR); Horgan, Briony5 (AUTHOR); Garczynski, Bradley9 (AUTHOR); Rice, Melissa9 (AUTHOR); Bell, James F.10 (AUTHOR); Maki, Jusin N.7 (AUTHOR); Hamran, Svein‐Erik11 (AUTHOR); Vaughan, Alicia12 (AUTHOR); Simon, Justin I.13 (AUTHOR); Kanine, Oak6 (AUTHOR) |
| Source: |
Journal of Geophysical Research. Planets. Jan2026, Vol. 131 Issue 1, p1-45. 45p. |
| Subject Terms: |
*Valleys; *Crater lakes; *Lake hydrology; Mars (Planet); Sedimentology; Terraces (Geology); Biostratigraphy; Mars rovers |
| Abstract: |
Martian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover‐based investigations of ancient habitability. The Mars 2020 Perseverance rover spent ∼85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave‐up bedding structure consistent with a young channel‐fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining‐up sequence from coarse‐grained sediments up to pebble‐conglomerates (the Tuff Cliff member) into a ≥10‐m‐thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix‐supported granule‐conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix‐supported, boulder‐conglomerate (the Mount Spoonhead member), interpreted as a high‐energy debrite derived from the watershed. The sequence is capped by cross‐stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs ∼10–50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late‐stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley‐confined lake upstream. Plain Language Summary: Between June and August 2024, the Perseverance rover investigated sedimentary rocks exposed in a dried‐up river valley that once fed an ancient lake in Jezero crater, Mars. This study analyses image data collected by Perseverance to describe these rocks, called the "Bright Angel" formation, and determine their depositional environment. Layers of rock in the Bright Angel formation are inclined into the center of the channel, suggesting they were deposited into the valley rather than being an older rock unit exposed by erosion of the channel. Somewhat surprisingly, most of the Bright Angel formation consists of fine‐grained, thinly layered mudstone deposited in a calm, lake setting by suspension settling of clay‐ and silt‐sized particles, rather than sediment consistent with river deposits. Rock units with pebbles and cobbles mixed with mudstone were most likely deposited as muddy debris flows entering the lake. Other pebble‐rich rocks near the edge of the valley preserve evidence for currents generated by flowing water, and were likely laid down at the lake margin by rivers. These lake deposits sit tens of meters above the lake level expected at Jezero crater, suggesting a blockage may have dammed the valley, forming a separate, upstream lake confined to the channel. Key Points: The Bright Angel formation preserves diverse, mudstone‐dominated sedimentary facies indicative of a fluvio‐lacustrine environment3D bedding measurements indicate that the valley floor unit has a concave‐up structure, consistent with a young, channel‐fill depositLacustrine conditions may have been facilitated by a blockage of Neretva Vallis, leading to the formation of a valley‐confined lake [ABSTRACT FROM AUTHOR] |
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| Database: |
GreenFILE |