LABORATORY ANALYSIS OF ROCK SAMPLE SUITES FROM A MARS ROVER SIMULATION CONDUCTED ON GREEN RIVER FORMATION SPECIMENS, UINTAH BASIN, UTAH

The Mars 2020 Rover has a primary mission goal of finding biosignatures. Testing protocols for efficient biosignature identification is an important step to finding biosignatures on Mars’ surface. The Geo-Heuristic Operational Strategies Tests (GHOST) are designed to determine the effectiveness of rover decision-making protocols in finding preserved evidence of biologic activity on Mars. In 2017, the GHOST field project used a “roverless roving” approach to compare the efficiency of two traverse methods to identify biosignatures at an analog Earth site (Eocene Green River Formation). This portion of the project focuses on the laboratory analysis of samples collected by each traverse team, as an analog for the sample-collection portion of the 2020 mission. Our aim of this study is to determine whether decision-making during the tested (linear and walkabout) traverse protocols produces sample suites that differ substantially in their potential for environmental reconstruction and biosignature identification.

Samples from both traverses include limestone, and the sample set from the walkabout traverse also includes an organic-rich shale. Samples were characterized via hand sample, thin section, x-ray diffraction, and cathodoluminescence. These data, combined with field observation, indicate deposition in a shallow water environment and subsequent low-temperature diagenesis. At least one limestone in each sample set has macroscopic features consistent with microbial origin, and the organic-rich nature of the shale sample suggests high biosignature preservation potential. Based on these results, total organic carbon and trace element analyses were conducted. All samples contain organic carbon, and trace element data are consistent with habitable aqueous conditions.

In summary, both traverse methodologies resulted in a sample suite with a high likelihood of biosignature preservation. The walkabout traverse recovered a greater diversity of sample types compared to the linear traverse, providing an additional dimension of environmental and biosignature context. The preliminary conclusions of this study are that rover observations and a limited sample suite can correctly identify the geology and biosignature potential of a region of interest.