Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p41b1281c&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P41B-1281
Physics
5464 Remote Sensing, 5470 Surface Materials And Properties, 6225 Mars
Scientific paper
The strong infrared signature of coarse-grained hematite led to the selection of Meridiani Planum as the landing site for Opportunity. This spectral signature was found to correspond to the ubiquitous spherules and their fragments that are a lag deposit on the upper plains surface. It was commonly thought that the only contribution to the infrared signature was from these small concretions. Recent analysis of the sulfate- dominated outcrop has shown that outcrop material that has a stronger hematite signature in Pancam images also have a weak, but identifiable feature of "coarse" hematite in Mini-TES spectra. This suggests that the thermal infrared wavelengths may be sensitive to a finer, distributed component of hematite, in addition to the spherules. We have analyzed concurrent Pancam and Mini-TES observations of typical soils taken periodically in the traverse from Endurance crater south toward Victoria crater in order to explore the correlation between the hematite signature observed by Mini-TES and the amount of cover by spherules and their fragments as seen by Pancam. Sixty coordinated observations of soils in the near field were made between sols 70 and 800. Of these, many of the Pancam images were acquired with only 6 or 7 filters, and many Mini-TES spectra were taken late in the day so that surface temperatures were cold and the sky contribution inverted. Approximately 25 observations were found to have both good Pancam coverage (full 13 filter) and high quality Mini-TES spectra. Coverage by spherules was determined using unsupervised classification on color ratios that enhance the appearance of "berries" against the background soils. Mini-TES band strength was determined using the feature near 550cm-1. Both berry cover and Mini-TES band strength vary strongly in the data set; however, surprisingly, there is very little correlation between area covered by berries and infrared hematite band strength. This may be due to the larger field of view of Pancam, but also suggests that Mini-TES is sensing an additional component of hematite in the soils, not just concretions. This has implications for the interpretation of both APXS and Mössbauer spectrometer data, both of which must assume an areal mixture of berries and soil in order to extract compositions of either endmember.
Calvin Wendy M.
Shoffner J. D.
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