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D. Rogers, J. L. Bandfield, P. R. Christensen (Arizona State University)
Recently Bandfield et al. (2000)  used MGS Thermal Emission Spectrometer (TES) data to identify two primary spectral signatures from Martian low-albedo regions; these correspond to basalt , and basaltic andesite compositions. Using these spectral shapes, Bandfield et al. (2000)  globally mapped the distribution of the two volcanic compositions at a scale of one pixel per degree. They concluded that the basaltic composition was restricted to the older, southern highlands, while the basaltic andesite composition displays high concentrations primarily in the younger northern lowlands.
This work has performed more detailed examinations that have identified small isolated regions of basalt in the northern lowlands of Mars. The areal distributions of basalt are mapped for these regions, at a scale of 32 pixels per degree. Two of these regions, located in the Nilosyrtis Mensae area (20-50N, 270-300W), are characterized using TES compositional, thermal inertia, and albedo datasets, as well as Viking, MOC, and MOLA datasets. The first region (29N, 285W), has a surface composed of ~80 region (45N, 295W), has a surface composition of ~70 thermal inertias, characteristic of sand-sized particles [3,4], and low albedos.
The discovery of these basalt regions in the northern lowlands differs slightly from the previous results of Bandfield et al. (2000) , in that upon closer examination, basalts are not restricted to the older southern highlands. Two possibilities for the origin of these northern hemisphere basalt regions are: 1) sand-sized particles have been transported from the southern highlands and deposited, or 2) the basalts are locally derived. Using combined datasets to characterize the properties and relationships between surface units may help determine the origin and relative age of these basalts.
Bandfield, J. L., V. E. Hamilton, and P. R. Christensen (2000), Science, 287, 1626-1630. Christensen, P. R., J. L. Bandfield, M. D. Smith, V. E. Hamilton, and R. N. Clark (2000), J. Geophys. Res., 105, 9609-9621. Presley, M. A. and P. R. Christensen (1997), J. Geophys. Res., 102, 9221-9229. Palluconi, F. and H. H. Kieffer (1981), Icarus, 45, 415-426.
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