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Several measurements, including the data from the laser spectrometer in theSample Analysis at Mars instrument suite on the Curiosity Rover in Gale crater,have measured seasonal variations in atmospheric methane at the 0.7 ppbv (partsper billion volume) level. As a result, models have been proposed to understandthe methane production including novel chemical, geological, meteorological,and biological mechanisms. Biological models often rely on methanogenicextremophile archaea which might be similar to some Earth based organisms whichcan be studied exhaustively in a laboratory setting. Such organisms mightthrive in a subsurface ecosystem involving water and methane and as such couldleave a unique biosignature in the Martian regolith that could be preservedover extended periods of time. The resulting mixture of carboxyl, acetyl andhydroxyl groups blended with the metallic sulfates and regolith constituentscould produce a Raman signature detectable on the next rover mission if theconcentration is high enough. Here we measure the 532 nm and the 780 nm Ramanspectra of a variety of molar concentrations of several hydrated metallicsulfates mixed with JSC-1 Martian regolith simulant to identify the signatureconcentration thresholds for the isolated C=O Raman peak from acetic acid. Wefind a Raman peak removed from most fragmented molecular Raman bands near 1608cm-1 using the 532 nm laser for the Fe and Mg sulfates to yield a threshold inthe 120 - 160 ppmv range for a cutoff S/N of 2.

Raman Detection Threshold Measurements for Acetic Acid in Martian Regolith Simulant JSC-1 in the Presence of Hydrated Metallic Sulfates