HR: 0800h
AN: P41B-0935    [Abstracts]
TI: Thermophysical Characterization of Terrestrial Alluvial Fans, With Applications to Mars
AU: * Moersch, J E
EM: jmoersch@utk.edu
AF: University of Tennessee, Dept. of Earth and Planetary Sciences 1412 Circle Dr., Rm 306, Knoxville, TN 37996 United States
AU: Whisner, S C
EM: geowhis@utk.edu
AF: University of Tennessee, Dept. of Earth and Planetary Sciences 1412 Circle Dr., Rm 306, Knoxville, TN 37996 United States
AU: Hardgrove, C
EM: chardgro@utk.edu
AF: University of Tennessee, Dept. of Earth and Planetary Sciences 1412 Circle Dr., Rm 306, Knoxville, TN 37996 United States
AB: Visible and infrared spectral remote sensing are currently being used to map lithologic variation on Mars, but these techniques are only sensitive to a depth equivalent to a few times the wavelength of observation (several 10's of microns at most). Thus, a fine regolith can make it difficult to characterize the geology of a surface based on spectral properties. This problem can be partially ameliorated by using thermal infrared temperature images. The temperature of the surface is controlled by material within approximately one diurnal thermal skin depth (typically a few cm) of the surface. Thermal images "see below" thin, spectrally obscuring surface layers, and enable the mapping of some underlying geologic heterogeneities (but not mineral compositions). Temperature variation is related, in part, to differences in thermal inertia, which in turn are related to lithology, particle size, degree of induration, and (for Earth) moisture content. THEMIS (and other) images of the Martian surface reveal a variety of features that may be the result of sedimentary processes. Earth analogs have been proposed for many of these features, but very little terrestrial analog work has been done to establish whether particular classes of sedimentary features have distinctive spatial-thermophysical signatures. Sedimentary processes often lead to sorting of grain sizes and/or varying degrees of cementation, so it is reasonable to expect that such signatures might exist. Here we present the results of a preliminary study of alluvial fans in Death Valley. As seen from above in ASTER nighttime thermal infrared images, these fans display distinct "thermophysical facies." Each fan apex has a relatively high thermal inertia, mid-fan areas have intermediate thermal inertias, and distal terminus areas have relatively low thermal inertias. This pattern of thermal inertias is consistent with field-based grain size studies that have been conducted on other debris flow-dominated fans in the area. We have also collected ground-based thermal images of one fan over a 24-hour insolation cycle in order to construct a "hypertemporal image cube" in which each spatial pixel contains a complete diurnal temperature curve. Principle component transformation of this unique data product allows us to separate the effects of surface geometry, shadows, and thermal inertia on surface temperatures. Our intent is to collect more such observations of alluvial fans and other sedimentary structures and compare them with nighttime THEMIS images of proposed analog structures on Mars.
DE: 4863 Sedimentation (1861)
DE: 5419 Hydrology and fluvial processes
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005