Measurements to Estimate the Spectrometric Detection Limit for Carbonates in Martian Soil

Abstract

Theoretical considerations of Mars climate evolution and conceptions about the weathering processes of Martian crustal rocks suggest that carbonate minerals might be present as likely secondary minerals in the soil and dust on Mars. Until now, however, no clear spectral evidence for carbonates on the surface on Mars has been found. (With the exception that Pollack et al. detected a 6.7 m absorption band that was tentatively assigned to carbonate or bicarbonate anions in a distorted crystalline site status in the atmospheric dust). Therefore the search for carbonate on Mars goes on. In the present study palagonite (an amorphous ferric-iron silica gel) and tholeiite (a basalt) are used as two Martian soil analogue materials and mixed with various percentages of carbonates (siderite, dolomite). By measurement of the samples' spectral reflectace in thewavelength range 1 to 17 muem it is investigated which spectral contrast (or band intensity) results at the diagnostic wavelengths for the various carbonate contents. The data obtained can be used to estimate limits for the spectrometric detection of these minerals.