Infrared and Raman Spectra of Organic-Bearing Shales
infrared, raman, clays, organics, shale, Mars
Clay minerals have been observed to be abundant and varied on Mars and most of them are associated with ancient Noachian terrains. It has been suggested that on Earth, clays are important for habitability and organic preservation. Studies of Earth’s carbon budget indicate ~68% of organics are stored in clays and shales of Earth’s crust. Clays have high surface areas and as a result, organic carbon content in clays is relatively high due to adsorption processes. It also has been suggested that if organics and clays form synchronously, the preservation of biosignatures may be more resistant to weathering processes, due to the chemical equilibration between organics and sedimentary rocks. Previous studies suggest that long-term preservation of microbial biosignatures on Mars may occur in rapid burial processes in find-grained clay-rich sediments, as anaerobic conditions due to quickly reduced porosity and permeability may slow the degradation of organics. Geologic analysis of the clay mineral deposits near Mawrth Vallis indicates that they are early-to-mid Noachian in age and were likely deposited in a sedimentary environment. The clay-bearing deposits are part of a set of layered rocks (>600 m thick) that contain interbedded, buried craters. If life ever existed on Mars, its record is likely to be found in sedimentary rocks that achieved kilometer-scale thicknesses and are rich in clay minerals. This archive contains infrared and Raman data of organic matter stored in terrestrial clay-rich sediments to gain insights into the potential formation or preservation conditions of biosignatures in clay-rich sediments, and aid the search for biosignatures on Mars.
Che, C. S. Parvez, and T. D. Glotch (2016), Spectroscopic study of biosignatures in clay-rich sediments: Implications for Martian astrobiological exploration, Lunar Planet. Sci., XLVII, abstract 1692.