Mars

Diagenetic History and Biosignature Preservation Potential of Fine-Grained Rocks at Hogwallow Flats, Jezero Crater, Mars

By Keith Cowing

Status Report

JGR Planets

December 10, 2024

Filed under astrogeology, biosignature, Drilling, fine-grained clastic sedimentary rocks, geology, Hogwallow Flats, imaging, Jezero Crater, JGR Planets, Mars, Mars Sample Return, Mastcam-Z, Perseverance Rover, rover, Shenandoah, Spectroscopy, SuperCam

Diagenetic History and Biosignature Preservation Potential of Fine-Grained Rocks at Hogwallow Flats, Jezero Crater, Mars — Visible wavelength decorrelation stretch (DCS) of Mastcam-Z image (Sol 676, zcam03518) demonstrating the spectral diversity of the Shenandoah formation near Hawksbill Gap showing stratigraphic members of the Shenandoah formation (from Stack et al. (2024)). Decorrelation stretch is L2 (754 nm) L5 (528 nm) and L6 (442 nm) where red, orange and magenta hues are associated with materials exhibiting variable states of oxidation and green to blue are ferrous minerals (e.g., olivine, pyroxene) combined with variable dust cover (Vaughan et al., 2023). — JGR Planets

The Mars 2020 Perseverance rover discovered fine-grained clastic sedimentary rocks in the “Hogwallow Flats” member of the “Shenandoah” formation at Jezero crater, Mars.

The Hogwallow Flats member shows evidence of multiple phases of diagenesis including Fe/Mg-sulfate-rich (20–30 wt. %) outcrop transitioning downward into red-purple-gray mottled outcrop, Fe/Mg clay minerals and oxides, putative concretions, occasional Ca sulfate-filled fractures, and variable redox state over small (cm) spatial scales.

This work uses Mastcam-Z and SuperCam instrument data to characterize and interpret the sedimentary facies, mineralogy and diagenetic features of the Hogwallow Flats member. The lateral continuity of bedrock similar in tone and morphology to Hogwallow Flats that occurs over several km within the western Jezero sedimentary fan suggests widespread deposition in a lacustrine or alluvial floodplain setting.

Following deposition, sediments interacted with multiple fluids of variable redox state and salinity under habitable conditions. Three drilled sample cores were collected from this interval of the Shenandoah formation as part of the Mars Sample Return campaign. These samples have very high potential to preserve organic compounds and biosignatures. Drill cores may partially include dark-toned mottled outcrop that lies directly below light-toned, sulfate-cemented outcrop.

This facies may represent some of the least oxidized material observed at this interval of the Shenandoah formation. This work reconstructs the diagenetic history of the Hogwallow Flats member and discusses implications for biosignature preservation in rock samples for possible return to Earth.
Key Points

Fine-grained clastic sedimentary rocks at the Hogwallow Flats member underwent limited diagenesis
Diagenesis may have occurred in a lake or a shallow river plain and later when the sediments were shallowly buried
Mottling features, sulfates and clay minerals within drilled rock core samples for Mars Sample Return have high astrobiological potential

Diagenetic History and Biosignature Preservation Potential of Fine-Grained Rocks at Hogwallow Flats, Jezero Crater, Mars, JGR Planets (open access)

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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