In Situ Measurements Of Ionic Motion Directly In Planetary Soils

Paleoclimate and environmental information can be extracted at a landing site from soil analyses and characterization, including whether water was a significant weathering agent. Terrestrial studies have demonstrated a close relationship between the depositional environment and the physical and chemical properties of the sediment/soils. If microbial life exists near the surface of Mars, then a close examination may detect coatings on sand or silt grains from the release of organic compounds, which are capable of sequestering or chelating ions from primary minerals or secondary weathering compounds. The search for life is a primary goal of NASA's planetary exploration program. The search is in itself tiered both in the life detection approach (present or past and level on the life detection pyramid) and in the survey method (scale, range, specificity) employed. A fundamental focus is on gathering evidence for water in the planetary near-surface. Current in-situ instruments are typically indirect, identifying minerals recognized from terrestrial experience as being caused by water-induced processes from measurements of elemental composition. IR reflectance spectra, or morphology using point instruments (e.g. APXS, Mossbauer, microscopic imager) do not distinguish between geologic events and present ones. Neutron spectrometers, on the other hand, identify pockets of hydrogen enrichment, which may or may not correlate with water in the planetary environment. Moreover, these instruments also require the rover to be stationary limiting their suitability for large-scale surveys. Characterizing potential habitats for life requires more unambiguous methods to detect water and a fuller characterization of planetary soils once water is found. The above instruments are not adequate for this larger task. Laboratory analytical instruments -- Mars Environmental Compatibility Assessment (MECA)/Phoenix-Wet Chemistry Lab (WCL), Trace Evolved Gas Analyzer (TEGA), Mars Oxidation Experiment (MOD) -- on the other hand, require extensive sample handling and/or consumables, limiting their use in large-scale surveys. Our instrument addresses the life detection problem by providing a tiered set of measurements of increasing complexity in undisturbed native planetary soils. The sensor suite will first detect, then quantify (1) the presence of water/ice, (2) ionic motion and (3) existing reduction-oxidation (REDOX) couples in the soils. From this characterization, we will infer potential energy sources for life in the soil habitat. The instrument provides this data over many samples, potentially while the rover is in motion, its minimal sample handling being consistent with the needs of surveying.