A Lacustrine Paleoenvironment Recorded at Vera Rubin Ridge, Gale Crater: Overview of the Sedimentology and Stratigraphy Observed by the Mars Science Laboratory Curiosity Rover

For similar to 500 Martian solar days (sols), the Mars Science Laboratory team explored Vera Rubin ridge (VRR), a topographic feature on the northwest slope of Aeolis Mons. Here we review the sedimentary facies and stratigraphy observed during sols 1,800-2,300, covering more than 100 m of stratigraphic thickness. Curiosity's traverse includes two transects across the ridge, which enables investigation of lateral variability over a distance of similar to 300 m. Three informally named stratigraphic members of the Murray formation are described: Blunts Point, Pettegrove Point, and Jura, with the latter two exposed on VRR. The Blunts Point member, exposed just below the ridge, is characterized by a recessive, fine-grained facies that exhibits extensive planar lamination and is crosscut by abundant curvi-planar veins. The Pettegrove Point member is more resistant, fine-grained, thinly planar laminated, and contains a higher abundance of diagenetic concretions. Conformable above the Pettegrove Point member is the Jura member, which is also fine-grained and parallel stratified, but is marked by a distinct step in topography, which coincides with localized meter-scale inclined strata, a thinly and thickly laminated facies, and occasional crystal molds. All members record low-energy lacustrine deposition, consistent with prior observations of the Murray formation. Uncommon outcrops of low-angle stratification suggest possible subaqueous currents, and steeply inclined beds may be the result of slumping. Collectively, the rocks exposed at VRR provide additional evidence for a long-lived lacustrine environment (in excess of 106 years via comparison to terrestrial records of sedimentation), which extends our understanding of the duration of habitable conditions in Gale crater. Plain language summary The primary goal of the Mars Science Laboratory Curiosity rover mission is to explore and assess ancient habitable environments on Mars. This requires a detailed understanding of the environments recorded by sedimentary rocks exposed at the present-day surface in Gale crater. Here we review the types of sedimentary rocks exposed at a location known as Vera Rubin ridge. We find that the rocks at Vera Rubin ridge record an ancient lake environment and are a continuation of underlying lake deposits. Ancient lake deposits are highly desirable targets in the search for habitable environments, due to their ability to concentrate and preserve organic matter. This study significantly expands the duration of habitable conditions that can be confirmed through ground truth of sedimentary rocks and provides a framework for interpreting strata that lie ahead as Curiosity continues to explore Aeolis Mons.