SPECTROSCOPIC IDENTIFICATION OF CARBONATES IN THE MARTIAN DUST. J. L. Bandfield, T. D. Glotch, and P. R. Christensen, Department of Geological Sciences, Arizona State University, Tempe AZ (joshband@asu.edu).
Lunar and Planetary Science XXXIV (2003) 1723.pdf
"Introduction: Carbonates play a significant determining the history of the Martian atmosphere, geology, and hydrology. Their presence and properties
can give useful information about the specific environment in which they formed in the past. The work
presented here demonstrates that the spectral character of Mars is consistent with and unique to the presence of small amounts of carbonates within a fine particulate dust."
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1723.pdf

Bob Clark