Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p51b1431h&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P51B-1431
Mathematics
Logic
[5464] Planetary Sciences: Solid Surface Planets / Remote Sensing, [5470] Planetary Sciences: Solid Surface Planets / Surface Materials And Properties, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Interior Layered Deposits (ILD) can potentially reveal climate variation on Mars. Many ILD successions are found in equatorial regions within large impact craters such as Becquerel Crater, 22°N, 353°E. We consider the role of water in the formation of the ILDs which contain light-dark cyclic layers on the metre scale. Various formation models have been proposed; including a lacustrine event, wind-blown sediments or a similar mechanism to the North Polar Layered Deposits (NPLD) [1,2,3]. We hypothesise that the sediments are analogous to the current NPLD which suggests a climatic control dominated by orbital forcing [2,3,4] and deposition from the air rather than from water. CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) onboard Mars Reconnaissance Orbiter (MRO) offers the opportunity for interpretation of remote sensing hyperspectral data with extensive coverage of the surface of Mars. CRISM can help assess the role of water in the formation of ILDs by indicating the presence, or lack of, hydrated minerals such as clay or sulphates. The currently supported analysis method uses the CRISM Analysis Tool (CAT) which results in band ratio mineralogical maps [5] used to guide the extraction of spectra which are compared to a reference library for identification [6,7,8]. This process uses a dusty, spectrally indistinct profile with which to normalise the data to remove topographical and residual atmospheric effects; emphasising a dominant mineral signature. This method has shown a lack of hydrated mineral signatures in the Becquerel Crater sediments which is consistent with the orbital forcing hypothesis. We present a comparison of the capabilities and limitations of a variety of multispectral and hyperspectral methods, used as standard in other areas of remote-sensing, when applied to CRISM, using CAT and ENVI 4.7 image processing software. These include Principal Components Analysis (PCA) and Minimum Noise Fraction (MNF) transforms, which effectively reduce the redundancy often found in hyperspectral data. Tests have been conducted using the Nili Fossae region that has been well characterised in published works [7]. PCA has improved the detail of the mineralogical maps in identifying the subtle changes in the spectral content, aiding the selection of whole-pixel spectra for further analysis. The MNF transform method has opened up the opportunity for sub-pixel analysis using partial or full linear unmixing to extract a quantitative abundance measurement. Results from Nili Fossae support the previous identifications and abundances of fayalite, smectite and carbonate. [1] Kargel (2004) Springer, 978-1852335688 [2] Laskar et al. (2004) Nature 419, 375-377 [3] Bridges et al. (2008) LPSC #1913 [4] Hill et al. (2010) LPSC #2227 [5] Pelkey et al. (2007) JGR 112, E08S14, 18 [6] Bishop (2008) Science 321, 5890, 830-833 [7] Mustard (2008) Nature 454, 305-309 [8] Ehlmann (2009) JGR 114, E00D08, 33
Ambrosi Richard M.
Bridges John
Davies S. J.
Hill K. S.
Smith Kester
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