Rock Texture and Structure at Sub-Millimeter Scales in Jezero Crater, Mars, Using the SHERLOC WATSON Camera

Bedrock exposed on the present-day floor of Jezero crater preserves rocks with a wide variety of outcrop expressions and surface textures. Images from the cameras aboard the Perseverance rover show materials that range from highly indurated, apparently structureless, and higher-relief cobbles and boulders to strongly eroded, crumbly, and low-relief bedrock patches. The spatial resolution of the rovers mast cameras, however, combined with the prevalence of wind sculpted and polished surfaces, make it difficult to identify features that are critical to interpreting the origin and diagenesis of geologic materials, such as mm-scale laminations. By contrast, WATSON (Wide Angle Topographic Sensor for Operations and eNgineering), one of two camera subsystems of the SHERLOC instrument, is a color camera designed for hand lens-scale imaging of rock surfaces. As of Sol 150, WATSON has imaged 16 unique surface targets since landing, with images at scales between 21 and 100 m/pixel. Here we use WATSON images to explore rock textures within Jezero Crater. To avoid challenges posed by the presence of aeolian dust adhering to rock surfaces, the SHERLOC team has, to the extent possible, focused on surfaces that are either naturally dust-free, or which have had some dust removed via SuperCam LIBS analysis (see target Nataani in Figure 1). While wind erosion, which produces both sculpted and polished surfaces, continues to challenge interpretation, a number of WATSON targets reveal irregularly shaped red patches that obscure the underlying rock surface, and are preliminarily interpreted as surface coatings. Such features are interpreted as potential iron oxide coating and may reflect alteration of the rock surface during atmosphere exposure. WATSON images also reveal a surprising variation in primary features, including potential rounded, clast-like features (<250 m diameter), and cm-scale elongate features of uncertain origin. Continued use of the WATSON instrument, particularly after rock abrasion, is expected to yield critical details for discriminating among discrete rock types. Fig. 1. (Left) SHERLOC and WASTON, imaged on sol 30 by the right Hazard Camera during PIXL analysis. (Right) WATSON rock target Nataani with the middle portion of the image blown clean by the Supercam laser (pits below the yellow arrow).