Mathematics – Logic
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p21c0162k&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P21C-0162
Mathematics
Logic
5410 Composition (1060, 3672), 5415 Erosion And Weathering, 5419 Hydrology And Fluvial Processes, 5464 Remote Sensing, 5470 Surface Materials And Properties
Scientific paper
We investigate the geological context and morphology of hematite deposits in Valles Marineris using data from the Thermal Emission Spectrometer (TES), the Thermal Emission Imaging Spectrometer (THEMIS), Mars Orbiter Camera (MOC), and Mars Orbital Laser Altimeter (MOLA). Observations indicate two classes of deposits within the canyon system. Deposits in Capri Chasma are in-place layered materials at the base of a stack of layers deposited on older chaotic terrain. Deposits in central Valles Marineris (Ophir and Candor Chasmata) are concentrated in topographic lows or benches that are adjacent to bright, layered, sulfate-rich materials. These deposits likely represent hematite-rich lag deposits weathered out of more friable materials, such as adjacent layered deposits. The Capri Chasma hematite deposits are similar in appearance and geological context to the deposit mapped in Aram Chaos. If the central Valles Marineris deposits are lag deposits as described above, they would be comparable to the Meridiani Planum hematite deposits. These results indicate that conditions in each of these two regions of Valles Marineris may have been similar to conditions at Aram Choas and Meridiani Planum at the time of hematite formation. Although two distinct categories of deposit can be established based on morphology and context, all hematite deposits on Mars share compositional commonality. The thermal infrared spectral shape of hematite as derived from TES data is common to all hematite sites so far investigated. Additionally, all sites share similar compositional context. Results from the Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite (OMEGA) team show that sulfate-rich materials occur in, or near, all of the TES identified hematite sites. The hematite is also mixed with basaltic materials as mapped by TES and THEMIS. Researchers have speculated on a variety of mechanisms for the formation of hematite on Mars, but the compositional similarities of all hematite exposures may indicate that all hematite on Mars formed through a similar mechanism. The two distinct categories of deposit may indicate that there were subtle differences in the depositional, post-depositional, or erosional history of these two categories of deposit, but the hematite formation mechanism was most likely common to both categories.
Christensen Per Rex
Knudson Amy T.
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