Mathematics – Logic
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p31b1710r&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P31B-1710
Mathematics
Logic
[5410] Planetary Sciences: Solid Surface Planets / Composition, [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
The spatial distribution of surface compositions provides critical information needed to understand the formation of Martian crustal materials as well as the interactions between the surface, atmosphere, and hydrosphere. To this end, we present a new global map of major compositional provinces on Mars. The map was derived by applying statistical methods to new mineral distributions derived from Mars Global Surveyor Thermal Emission Spectrometer (TES) data. The new mineral distributions [1] were calculated using a larger set of olivine and pyroxene compositions, and at a higher spatial resolution (8 pixels per degree), relative to previous global studies [e.g, 2]. Consistent with previous results [2], we find that: A) Syrtis Major and circum-Tharsis volcanic plains are compositionally distinct from other, older highland surfaces, B) lowland materials exhibit elevated abundance of "high-silica" phases (amorphous silica and/or poorly crystalline silicates), and C) northern Acidalia surfaces are compositionally distinct from those in southern Acidalia. New findings include the following: D) northwestern Syrtis Major shield materials are enriched in feldspar relative to southern Syrtis Major, E) within Thaumasia and Aonium Plana (Hesperian aged plains), there are possibly 3 different classes of mineral assemblage, and F) heavily cratered Noachian terrains including Terra Meridiani, Tyrrhena Terra, and Cimmeria Terra can be divided into at least two classes based on relative abundance of plagioclase and low-Ca pyroxene. These new reported classes exhibit spatial coherency over a scale of at least tens of km; select areas were verified using spectral ratios from individual TES orbits that cross compositional class boundaries. These spatial trends in mineral assemblage may partially reflect global variations in melt generation and magmatic processes, and may also partially reflect spatial variation in precipitation, erosion, and/or ice-related alteration. For example, the boundary observed in Acidalia (C) roughly coincides with a morphologic boundary identified by [3] that separates ice-bearing, dissected terrain and non-dissected terrain [4]. Within Syrtis Major, the differing compositions (D) may reflect changes in melt fractionation or assimilation that occurred during the construction of the Syrtis shield. Detailed comparison with surface age, morphology, drainage density [5] and predicted locations of groundwater upwelling [6] may provide insight into the controls on spatial variations in mineral assemblage. Based on the similarity of soil chemical compositions between landing sites in Gusev Crater and Meridiani, it has been hypothesized that dark soils may be globally homogeneous [7]. This would imply that crustal compositions exposed at the surface are relatively homogeneous or that impact/aeolian processes have homogenized the dark soil fraction of the Martian surface layer. Either way, this hypothesis is not supported by remote sensing observations. [1]Koeppen and Hamilton, 2008, JGR-Planets [2]Rogers, and Christensen, 2007, JGR-Planets [3]Mustard et al. 2001, Nature. [4] Kraft et al. 2009, AGU [5] Hynek et al. 2011, JGR-Planets [6] Andrews-Hanna and Lewis, 2010, JGR-Planets [7] Yen et al. 2005, Nature.
Hamilton Victoria E.
Rogers David
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