Evidence for a Diagenetic Origin of Vera Rubin Ridge, Gale Crater, Mars: Summary and Synthesis of Curiosity's Exploration Campaign

Abstract

This paper provides an overview of the Curiosity rover's exploration at Vera Rubin ridge (VRR) and summarizes the science results. VRR is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mount Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray-colored patches concentrated toward the upper elevations of VRR, and these gray patches also contain small, dark Fe-rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric-related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence

Analyses of High‐Iron Sedimentary Bedrock and Diagenetic Features Observed With ChemCam at Vera Rubin Ridge, Gale Crater, Mars: Calibration and Characterization

“…Consequently, as the variability in iron abundance was mainly observed between different targets and to a lesser extent in the same ChemCam raster sequence, we can assume that grain size has only a second-order effect. In addition, neutron-absorbing elements (the main elements on Mars are Fe and Cl; Hardgrove et al, 2011) measured by DAN in active mode show higher variability across the Jura member compared to Pettegrove Point and Blunts Point (Fraeman, Edgar, et al, 2020), indicating that our chemostratigraphic trends from target to target are qualitatively consistent with bulk-rock measurements in VRR. Figure 3b represents the average iron abundance per ChemCam target at VRR along the rover traverse.…”

APXS‐Derived Compositional Characteristics of Vera Rubin Ridge and Murray Formation, Gale Crater, Mars: Geochemical Implications for the Origin of the Ridge

“…Fe, Ti, Mn gray/blue patches and more typical bedrock are observed to occur at relatively high angles to the observed bedding (e.g., Figure 13 in Fraeman, Edgar, et al, 2020). Changes in provenance, lake water chemistry, or redox conditions at the sediment/water interface would be expected to result in compositional changes that follow the flat-lying stratigraphy.…”

“…All 10 of the instruments on Curiosity's payload were utilized during the campaign to investigate VRR (see Fraeman, Edgar, et al, 2020). These included the navigation and science cameras, as well as internal and external geochemical and mineralogical instruments.…”

“…Both members exhibit color variations, which are more prevalent in the Jura member. A further distinction has been made between patches of bedrock that appear bright gray/blue in color-stretched HiRISE imagery and the more typical red/tan strata of VRR (Fraeman, Edgar, et al, 2020; Figures 2 and S6). These bright gray/blue patches are concentrated within the upper VRR Jura member but are also observed within the Pettegrove Point member, albeit less commonly (Figure 2).…”

Iron Mobility During Diagenesis at Vera Rubin Ridge, Gale Crater, Mars

“…VRR thus provides a unique opportunity to investigate redox processes on Mars but also to compare orbital observations and interpretations against the ground truth. As such, this topographic structure constitutes a key milestone in the rover's investigation of the Gale crater's geological history and its implications for past habitability on the planet (Fraeman et al, 2020).…”