  We analyze thermal emission spectra using the 2001 Mars Odyssey Thermal
Emission Imaging System (THEMIS) and the Mars Global Surveyor (MGS) Thermal
Emission Spectrometer (TES) to characterize grain size and mineralogical
composition of dunes at Hargraves crater, Mars. Thermal inertia and bulk
composition of the dunes were compared to inferred provenances from the thermal
infrared response of surface constituent materials. We use a Markov Chain Monte
Carlo (MCMC) technique to estimate the bulk amount of mineralogy contributed by
each inferred provenance to the dune field composition. An average thermal
inertia value of 238+/-17 Jm-2K-1s-0.5 was found for the dunes corresponding to
a surface composed of an average effective grain size of ~391+/-172 um. This
effective particle size suggests the presence of mostly medium sand-sized
materials mixed with fine and coarse grain sands. The dunes are likely
comprised of a weakly indurated surface mixed with unconsolidated materials.
Compositional analysis specifies that the dunes are comprised of a mixture of
feldspar, olivine, pyroxene, and relatively low bulk-silica content. Dune
materials were likely derived from physical weathering, especially eolian
erosion, predominantly from the crater ejecta unit at the crater, mixed with a
small amount from the crater floor and crater rim and wall lithologies -
indicating the dune materials were likely sourced locally.
