Hydrated Silica at Mawrth Vallis and Implications for Past Environment

Details Hydrated Silica at Mawrth Vallis and Implications for Past Environment Hydrated Silica at Mawrth Vallis and Implications for Past Environment

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p54a..04m&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P54A-04

Other

[5410] Planetary Sciences: Solid Surface Planets / Composition, [5464] Planetary Sciences: Solid Surface Planets / Remote Sensing, [6225] Planetary Sciences: Solar System Objects / Mars

Scientific paper

Hydrated silica has been identified in many outcrops in the Mawrth Vallis region [1-3] often mixed with Al-bearing phyllosilicates such as kaolinite and montmorillonite. To determine which form of hydrated silica could be mixed with the Al-phyllosilicates at Mawrth Vallis, spectra of intimate mineral mixtures were measured in the lab and compared to CRISM spectra (figure 1). The mixtures considered were: kaolinite-opal-A, kaolinite-montmorillonite, montmorillonite-obsidian, montmorillonite-hydrated silica (opal), and glass-illite-smectite. The best spectral matches with Martian data from our lab experiments are mixtures of montmorillonite and obsidian having 20 to 50 % montmorillonite or mixtures of kaolinite and montmorillonite with 25 to 50 % kaolinite. The spectra of clay mixtures with opal and of hydrothermally altered glass-illite-smectite did not represent as well the Martian spectra observed in this region. This suggests that a cryptocrystalline (obsidian) or crystalline form of hydrated silica is present at Mawrth Vallis rather than an amorphous form (opal-A) which has been identified elsewhere on Mars [e.g. 4]. References: [1] Bishop, J. L. et al. (2008) Science, 321, 830-833. [2] McKeown, N. K. et al. (2009) JGR- Planets, 114, E00D10. [3] Noe Dobrea, E. Z. et al. (2010) JGR- Planets, 115, E00D19. [4] Milliken, R. E. et al. (2008) Geology, 36, 847-850. Figure 1 (left) Spectra of montmorillonite-obsidian mixtures compared to CRISM spectra from FRT0000848D. (right) Spectra of kaolinite-montmorillonite and kaolinite-SiOH (opal-A) mixtures compared to CRISM spectra from HRL000043EC and FRT0000848D.

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