Hydrothermal Activity Generated By Impact Melt Emplacement On The Rim Of Ritchey Crater, Mars

Impact-induced hydrothermal systems have the potential to sustain long-lived aqueous environments throughout the history of Mars, yet their nature and distribution are not well-understood.

While post-impact hydrothermal alteration on Mars has traditionally been studied at central peaks, we reported similar processes within a well-preserved impactite stratigraphy across the inner rim of Ritchey crater.

This stratigraphy comprises a sheet unit overlying fragmented breccia, consistent with the emplacement of impact melt rocks on ballistic ejecta deposits, similar to features observed in complex craters on Earth. Analysis of CRISM hyperspectral data revealed alteration minerals including serpentine, chlorite, Mg-carbonate in fractured bedrock, veins, and erosional windows underneath the sheet unit.

These alteration minerals are unrelated to post-impact fluvio-lacustrine facies or pre-impact target bedrock. Instead, their formation is most plausibly attributed to the emplacement of hot impact melt and subsequent groundwater percolation through fractured bedrock at the crater rim.

The widespread distribution of the alteration minerals on the inner rim suggests that impact cratering can create extensive habitable environments. Our findings underscore the potential for alteration minerals at crater rims to preserve biosignatures, a key objective of the Mars 2020 mission at Jezero crater.

A Ritchey overview, CTX image mosaic (see Methods). B Eastern crater rim area of Ritchey, showing the smooth and dark-toned sheet unit. HiRISE grayscale and enhanced color images (ESP_011846_1515 and ESP_012914_1515) on CTX basemap. Cyan area: regions of interest (ROI a) used to extract average CRISM spectra in Fig. 3. Inset 1 at the bottom left shows the increasingly brecciated texture toward the margin of the sheet unit. C Close-up view of the sheet unit margin. Note the brecciated slope/escarpment of the sheet unit (see Fig. 2C for a 3D view). White arrows: fragmented breccia underlying the sheet unit. Yellow arrows: NE-SW ridges in the light-toned basement unit. Green arrow: dark-toned dike-like material in the sheet unit. Inset 1 shows decameter-long vertical structures (black arrows) across the escarpment of the sheet unit that resembles degassing pipes36 or hydrothermal channels37 in melt-rich breccia on Earth. Some of these vertical structures show side branches with varying shapes (white arrows). Inset 2 shows a carbonate-bearing basement rock with fractures or possible vein fillings (red arrows) related to the fault zone, see Fig. 3 ROI d for spectrum. D Comparison of the brecciated escarpment of the sheet unit (see Fig. 2A for 3D view) and a smooth escarpment of bedrock. The breccia and altered bedrock units are stratigraphically confined between the sheet unit to the NW and the dark-toned underlying bedrock unit in the SE. E Cross section of the impactite stratigraphy, see E–E’ in Fig. 1B. — Nature Communications via PubMed

Hydrothermal activity generated by impact melt emplacement on the rim of Ritchey crater, Mars, Nature Communications via PubMed

Astrobiology, Astrogeology,