Detectability of crystalline ferric and ferrous minerals on Mars

Telescopic and spacecraft spectroscopic and geochemical data have been used to constrain the surface mineralogy of Mars and to yield clues about past and present Mars surface weathering/alteration scenarios. Based primarily on their visible to near-IR reflectance properties, several terrestrial iron-bearing minerals have been either identified on Mars or proposed as Mars spectral analogs. Among these are crystalline hematite, pyroxenes, as well as poorly crystalline materials like nonophase hematite and palagonite. Other iron-bearing minerals include nontronite, magnetite, jarosite, and goethite and the have been proposed as Mars surface constituents based on Viking Lander measurements or geochemical modeling. If present on Mars, these materials likely appear as spectral mixtures at the coarse spatial resolution of remotely sensed data. The detectability of any of these components must be evaluated relative to the other components with which they occur. The primary goal of this study is to determine how much of any given mineral would have to be present for it to be detectable in remotely-sensed data. Here, the detectability of iron-bearing minerals was evaluated using detection threshold analysis (DTA), an analytical technique based on spectral mixture analysis.