Early diagenesis at and below Vera Rubin ridge, Gale crater, Mars

Abstract

Data returned by NASA’s Mars Science Laboratory Curiosity rover showed evidence for abundant secondary materials, including Fe‐oxides, phyllosilicates, and an amorphous component on and below Vera Rubin ridge in the Murray formation. We used equilibrium thermochemical modeling to test the hypothesis that altered sediments were deposited as detrital igneous grains and subsequently underwent diagenesis. Chemical compositions of the Murray formations’ altered components were calculated using data returned by the chemistry and mineralogy X‐ray diffraction instrument and the alpha particle X‐ray spectrometer on board Curiosity. Reaction of these alteration compositions with a CO2‐poor and oxidizing dilute aqueous solution was modeled at 25–100 °C, with 10–50% Fe3+/Fetot of the host rock. The modeled alteration assemblages included abundant phyllosilicates and Fe‐oxides at water‐to‐rock ratios >100. Modeled alteration abundances were directly comparable to observed abundances of hematite and clay minerals at a water‐to‐rock ratio of 10,000, for system temperatures of 50–100 °C with fluid pH ranging from 7.9 to 9.3. Modeling results suggest that the hematite–clay mineral assemblage is primarily the result of enhanced groundwater flow compared to the Sheepbed mudstone observed at Yellowknife Bay, and underwent further, localized alteration to produce the mineralogy observed by Curiosity.

Statistical Analysis of APXS‐Derived Chemistry of the Clay‐Bearing Glen Torridon Region and Mount Sharp Group, Gale Crater, Mars

“…Previous workers (for example, Bristow et al., 2019; Fraeman et al., 2020; Frydenvang et al., 2020; Rampe et al., 2020; Turner et al., 2021) have suggested the presence of a diagenetic front, along the ridge, overlain by a relatively impermeable caprock. Such a model is broadly compatible with APXS compositional data from Jura_VRR (Thompson et al., 2020).…”

“…Phyllosilicates are also less abundant in GT drill sites on or in contact with the overlying pediment (Hutton, Edinburgh) (6-8 wt.%) (Thorpe et al, 2022), associated with areas of alteration (Section 4.3.2; also Thompson et al, 2022). Previous workers (for example, Bristow et al, 2019;Fraeman et al, 2020;Frydenvang et al, 2020;Rampe et al, 2020;Turner et al, 2021) have suggested the presence of a diagenetic front, along the ridge, overlain by a relatively impermeable caprock. Such a model is broadly compatible with APXS compositional data from Jura_VRR (Thompson et al, 2020).…”

Overview of the Morphology and Chemistry of Diagenetic Features in the Clay‐Rich Glen Torridon Unit of Gale Crater, Mars

“…These diagenetic features are evidence for an extensive and longlived groundwater system that expands the window of habitability to the subsurface well after surface water retreated from the surface of Mars, due to the presence of redox-active elements (e.g., Fe, Mn, S), and elements required for life (e.g., S and P). Both early and late diagenetic events may have occurred to account for these observations (e.g., Turner et al, 2021).…”

“…Strata above Sutton Island (Blunts Point, Pettegrove Point, and Jura) likely represent lacustrine settings. The Pettegrove Point and Jura members have been overprinted by a later diagenetic event that may have formed the Vera Rubin ridge topographic feature (Edgar et al., 2020; Fraeman, Edgar, et al., 2020; Fraeman, Johnson, et al., 2020; Frydenvang et al., 2020; Rampe et al., 2020; Rivera‐Hernández et al., 2020; Thompson et al., 2020; Turner et al., 2021).…”

“…These diagenetic features are evidence for an extensive and long‐lived groundwater system that expands the window of habitability to the subsurface well after surface water retreated from the surface of Mars, due to the presence of redox‐active elements (e.g., Fe, Mn, and S), and elements required for life (e.g., S and P). Both early and late diagenetic events may have occurred to account for these observations (e.g., Turner et al., 2021). Observations have been made for both earlier cements (e.g., Comellas et al., 2021; Nellessen et al., 2019; Newsom et al., 2017; Rapin et al., 2019; Smith et al., 2021) and later sulfate filling fractures (e.g., Horgan et al., 2020; Lanza et al., 2016; Nachon et al., 2014, 2017).…”