Updated Perspectives and Hypotheses on the Mineralogy of Lower Mt.
Sharp, Mars, as seen from Orbit
Previous studies have shown that Mt. Sharp has stratigraphic variation
in mineralogy that may record a global transition from a climate more
conducive to clay mineral formation to one marked by increased sulfate
production. To better understand how small-scale observations along the
traverse path of NASA’s Curiosity rover might be linked to such
large-scale processes, it is necessary to understand the extent to which
mineral signatures observed from orbit vary laterally and vertically.
This study uses newly processed visible-near infrared CRISM data and
corresponding visible images to re-examine the mineralogy of lower Mt.
Sharp, map mineral distribution, and evaluate stratigraphic
relationships. We demonstrate the presence of darker-toned strata that
appears to be throughgoing with spectral signatures of monohydrated
sulfate. Strata above and below this zone are lighter-toned and contain
polyhydrated sulfate and variable distribution of Fe/Mg clay minerals.
Clay minerals are observed at multiple stratigraphic positions; unlike
the kieserite zone these units cannot be traced laterally across Mt.
Sharp. The kieserite zone appears to be stratigraphically confined, but
in most locations the orbital data do not provide sufficient detail to
determine whether mineral signatures conform to or cut across
stratigraphic boundaries, leaving open the question as to whether the
clays and sulfates occur as detrital, primary chemical precipitates,
and/or diagenetic phases. Future observations along Curiosity’s traverse
will help distinguish between these possibilities. Rover observations of
clay-bearing strata in northwest Mt. Sharp may be more reflective of
local conditions that could be distinct from those associated with other