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  • 1
    Publication Date: 2019-08-13
    Description: The Alpha Particle X-ray Spectrometers (APXS) onboard the Mars Exploration Rovers (MER) have measured the chemical compositions of over 400 samples on the surface of Mars. Fe and Mn are among the elements which are well established by this instrumentation. Fe2+ and Mn2+ have nearly the same ionic radii and distribute similarly in primary igneous rocks, maintaining a consistent Fe:Mn ratio. Upon exposure to an oxidative weathering environment, Fe 3+ and Mn4+ are commonly formed, and elemental fractionation can occur. Thus, altered samples will typically exhibit a Fe:Mn ratio different from precursor materials.
    Keywords: Space Sciences (General)
    Type: JSC-CN-19548 , Lunar and Planetary Science Conference; Mar 01, 2010 - Mar 05, 2010; The Woodlands, TX; United States
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: The purpose of this paper is to constrain the total water contents from crystal H2O and OH in several materials analyzed by the Mars Exploration Rovers (MER). Crystal H2O is part of the unit cell and cannot be removed without changing the structure. Minerals that contain only OH in their structures are anhydrous minerals containing hydroxyls, although they are formed as a product of aqueous activity and will decompose with evolution of H2O when heated. The crystal water and OH contents of a bulk material at the MER landing sites can be estimated from mineralogical composition, which is determined by a combination of Fe-mineralogy obtained by the Mossbauer Spectrometer and mineral abundances based upon the chemical composition determined by the Alpha Particle X-ray Spectrometer. Jarosite, along with Ca- and Mg-sulfates, have been suggested as the sulfur-bearing phases in Meridiani Planum outcrop. Models of various hydration states of Fe-, Ca-, and Mg-sulfates and other possible secondary phases suggest that 6 to 22 wt.% of the outcrop may occur as crystal H2O and/or OH (Clark et al., 2005). This estimate of water is consistent with measurements from the Odyssey orbiter, where 7 % H2O-equivalent H was measured down to a depth of approximately 1 m for the region (Feldman et al., 2004).
    Keywords: Space Sciences (General)
    Type: Goldschmidt 2007 Conference; Aug 19, 2007 - Aug 24, 2007; Cologne; Germany
    Format: application/pdf
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