USING ROVER-ANALOGOUS INSTRUMENTATION TO DISCRIMINATE BETWEEN VOLCANIC AND SEDIMENTARY PROCESS IN SUCCESSIONS DOMINATED BY IGNEOUS CHEMISTRY: THE TJÖRNES, ICELAND EXAMPLE

Many outcrops observed on Mars, including those at Jezero Crater, contain abundant layered material which lack extensive chemical alteration and may have undergone substantial aeolian modification. Such outcrops have proven challenging to discriminate among emplacement mechanisms. Features of volcanic flows, which might readily be identified on Earth by surficial textures and vesicular habits, are difficult to discriminate from sedimentary strata containing igneous clasts, wherein wind abrasion has modified surface textures and plucked sedimentary grains. Even the presence of a glass phase, common in volcanic rocks, is non-diagnostic, as these phases would be common in volcanic rocks but could also result from incorporation of glasses into a later sedimentary material.

We tested semi-autonomous rover science operations strategies to determine best practices suitable for interrogating the provenance of volcanic or sedimentary layers of similar igneous composition. Two field teams studied a 50 m vertical outcrop at Tungulending, Iceland, as an analog for a martian site containing interleaved layers of sedimentary and volcanic units. A Rover team commanded a human rover to execute observations based on common Mars rover sequences; the resulting data were used to identify and characterize the geologic history of the location. Results were compared to that of a Tiger team using traditional terrestrial field methods to interrogate the same site. The results of this test suggest that, in a succession dominated by igneous chemistry, the current rover-driven decision-making protocols are sufficient to provide data supporting an accurate first-order interpretation of a sequence of sedimentary and volcanic layers. Two of the most crucial datasets are: (1) handlens-scale images revealing grain morphology and relationships; (2) datasets that allow comparison between surface and bulk geochemistry. Additionally, certain sedimentary features can be difficult to confidently identify if they are not viewed at a specific distance/angle. Cross-bedding in particular appears to have an ideal distance and angle of viewing, and confident interpretations appear to require lateral scanning of the bed.