HR: 1340h
AN: P13D-1549    [Abstracts]
TI: Global Mineral Maps of Mars: Examination of Compositional Variation Within Solid Solution Series
AU: * Hamilton, V E
EM: hamilton@higp.hawaii.edu
AF: HIGP/University of Hawaii, 1680 East-West Rd., POST 504, Honolulu, HI 96822, United States
AU: Koeppen, W C
EM: koeppen@higp.hawaii.edu
AF: HIGP/University of Hawaii, 1680 East-West Rd., POST 504, Honolulu, HI 96822, United States
AB: We have produced updated global mineral maps from Mars Global Surveyor Thermal Emission Spectrometer (TES) infrared data using a spectral library that includes spectra of important phases that were not available in previous mapping efforts [1]. Our refined global mineral maps are broadly similar to those published previously using TES data, but improvements in our spectral library and discernible spatial correlations give us greater confidence that we can examine the distribution of not just mineral groups, but the distribution of phases within solid solution series. For example, variations in the abundances and distribution of several compositions across the Mg-Fe olivine series have been observed and confirmed manually [2]. We have tentatively identified pigeonite for the first time on a global scale, as well as larger fractions of orthopyroxene than were identified in previous TES-based mapping; these results have greater consistency with visible to near infrared (VNIR) data. Furthermore, some low-Ca pyroxene compositions appear to have distributions that correlate with Noachian (and Hesperian) terrains. High Ca (clino-) pyroxenes are dominated by intermediate Mg-Fe compositions (augite), and in particular, by a phase that has relatively high Ti content [3]. We observe spatially correlated distributions of compositions within the sulfate and phyllosilicate groups, although these remain to be confirmed through manual examination. Serpentines are not identified at detectable levels, suggesting that if they are present, their abundances are small (e.g., < ~10%). Noachian terrains are where many phases produced by aqueous alteration have been identified in VNIR data; regional variations in primary phase composition and abundance within these terrains almost certainly play a major role in determining what alteration phases are produced and at what abundances. Global mineral mapping at Mars thus provides critical context for understanding local-scale mineralogical variations, such as those that appear related to aqueous weathering of igneous lithologies in Noachian terrains. [1] Bandfield, J.L., JGR, 107, doi:10.1029/2001JE001510, 2002. [2] Koeppen, W. C. and V. E. Hamilton, JGR, submitted. [3] Hamilton, V.E., JGR, 108, doi:10.1029/2003JE002052, 2003.
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 5410 Composition (1060, 3672)
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting