Spectroscopic examinations of hydro- and glaciovolcanic basaltic tuffs: Modes of alteration and relevance for Mars

Hydro- and glaciovolcanism are processes that have taken place on both Earth and Mars. The amount of materials produced by these processes that are present in the martian surface layer is unknown, but may be substantial. We have used Mars rover analogue analysis techniques to examine altered tuff samples collected from multiple hydrovolcanic features, tuff rings and tuff cones, in the American west and from glaciovolcanic hyaloclastite ridges in Washington state and in Iceland. Analysis methods include VNIR-SWIR reflectance, MWIR thermal emissivity, thin section petrography, XRD, XRF, and Mössbauer spectroscopy. We distinguish three main types of tuff that differ prominently in petrography and VNIR-SWIR reflectance: minimally altered sideromelane tuff, gray to brown colored smectite-bearing tuff, and highly palagonitized tuff. Differences are also observed between the tuffs associated with hydrovolcanic tuff rings and tuff cones and those forming glaciovolcanic hyaloclastite ridges. For the locations sampled, hydrovolcanic palagonite tuffs are more smectite and zeolite rich while the palagonitized hyaloclastites from the sampled sites are largely devoid of zeolites and relatively lacking in smectites as well. The gray to brown colored tuffs are only observed in the hydrovolcanic deposits and appear to represent a distinct alteration pathway, with formation of smectites without associated palagonite formation. This is attributed to lower temperatures and possibly longer time scale alteration. Altered hydro- or glaciovolcanic materials might be recognized on the surface of Mars with rover-based instrumentation based on the results of this study

Results from the first geologic traverse on the topographic rim of a complex impact crater, Endeavour Crater, Mars

AbstractA geologic traverse along the rim of the 22-km-diameter Endeavour Crater by the Opportunity Mars rover has provided the first field geologic observations of outcrop-scale structure and stratigraphy at a complex impact crater, characteristics that were previously undocumented due to erosion of similar-size craters on Earth. Two findings of note are (1) the attitude of sheets, foliations, and contacts between rim impact breccias and pre-impact substrate is antiformal, the limbs dipping inward toward the center of the crater inside the crater rim and outward exterior to the crater rim; and (2) coherent blocks of crust segment the rim topographically and structurally into a series of right- and left-stepping elongate rises of variable size and orientation. These segments experienced differing magnitudes of uplift during crater formation along identified vertical scissors faults. Brecciation along the faults bounding rim segments created zones of enhanced subsurface fluid transport through the crater rim, potentially responsible for localized areas of aqueous alteration identified in outcrops near segment boundaries.</jats:p

MASTCAM MULTISPECTRAL AND CHEMCAM PASSIVE REFLECTANCE EXAMINATION OF DARK-TONED ROCKS FROM THE STIMSON TO UPPER GEDIZ VALLIS RIDGE IN GALE CRATER, MARS

International audienceCuriosity rover Mastcam multispectral data of dark-toned rocks from the in-situ Stimson formation to boulders on upper Gediz Vallis Ridge are described and put in context of the MSL mission