ASSESSING IDENTIFICATION OF TERRESTRIAL HYDROTHERMAL MINERALS WITH MARS ANALOG INSTRUMENTATION

Relict hydrothermal deposits on Mars are a key habitable niche and have been studied from orbiters and rovers. The alteration mineral assemblages provide constraints on the paleoenvironmental conditions (e.g., temperature, fluid chemistry, pH, redox, etc) and, thus, accurate quantification of these products is required for correct interpretations. A thorough characterization of hydrothermally altered deposits was conducted across multiple volcanic analog sites using Mars analog instrumentation. Field-portable VNIR and XRD as well as a Raman Laser Spectrometer (RLS) were used to analyze 100 samples of alteration products from basalt-hosted fumaroles and hot springs in Costa Rica, Nicaragua, and Iceland. Several analog sites were used to provide a wider range of potential alteration products. Mineral identifications for each sample were compared across the various instrumentation methods to investigate the accuracy and thoroughness of each analytical method as well as potential interactions, such as signal masking, with a number of mineralogical combinations.

Preliminary data indicates a roughly equal ability for sulfate identification between VNIR, XRD, and RLS, and a slight advantage for oxide identification via RLS, with VNIR also effective for Fe-oxide identification. As expected, phyllosilicate identification is most effective with VNIR, as well as identification of amorphous phases such as hydrated silica and palagonite. XRD is also highly effective at identification of the aforementioned phases. However, the need for ³2 wt % of a material for identification via XRD does result in missed trace materials that may be easily identified via VNIR or RLS. Mineralogy is a key input for assessing the aqueous history of Mars and its potential habitability. These results have bearing on the detection limits and accuracies of numerous instruments onboard the astrobiologically-minded investigations of the Curiosity rover and the upcoming ExoMars 2020 rover.