Spectral evidence for zeolite in the dust on Mars

Spectral features observed in Mars Global Surveyor Thermal Emission Spectrometer data (similar to 1670-220 cm(-1)) of martian surface dust provide clues to its mineralogy. An emissivity peak at similar to 1630 cm(-1) is consistent with the presence of an H2O-bearing mineral. This spectral feature can be mapped globally and shows a distribution related to the classical bright regions on Mars that are known to be dust covered. An important spectral feature at similar to 830 cm(-1) present in a newly derived average spectrum of surface dust likely is a transparency feature arising from the fine particulate nature of the dust. Its shape and location are consistent with plagioclase feldspars and also zeolites, which essentially are the hydrous form of feldspar. The generally favored visible/near-infrared spectral analog for martian dust, JSC Mars-1 altered tephra, does not display the similar to 830 cm(-1) feature. Zeolites commonly form from the interaction of low temperature aqueous fluids and volcanic glass in a variety of geologic settings. The combination of spectral features that are consistent with zeolites and the likelihood that Mars has (or had) geologic conditions necessary to produce them makes a strong case for recognizing zeolite minerals as likely components of the martian regolith. (C) 2003 Elsevier Inc. All rights reserved.