Orbital Identification of Carbonate-Bearing Rocks on Mars

Department of Geological Sciences, Brown University, Providence, RI02912, USA.
Science (Impact Factor: 31.48). 01/2009; 322(5909):1828-32. DOI: 10.1126/science.1164759
Source: PubMed

ABSTRACT Geochemical models for Mars predict carbonate formation during aqueous alteration. Carbonate-bearing rocks had not previously
been detected on Mars' surface, but Mars Reconnaissance Orbiter mapping reveals a regional rock layer with near-infrared spectral
characteristics that are consistent with the presence of magnesium carbonate in the Nili Fossae region. The carbonate is closely
associated with both phyllosilicate-bearing and olivine-rich rock units and probably formed during the Noachian or early Hesperian
era from the alteration of olivine by either hydrothermal fluids or near-surface water. The presence of carbonate as well
as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering,
proposed to be characteristic of Hesperian Mars, did not destroy these carbonates and thus did not dominate all aqueous environments.

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    • "face reduces the spectral information from minerals beyond the range of 2 . 6 lm wavelength . The contribution of ther - mal emissions and the lower signal - to - noise ratio of the detector have also been found around 3 lm and can also diminish impor - tant information from spectral signatures ( Wagner and Schade , 1996 ; Murchie et al . , 2007 ; Ehlmann et al . , 2008 ) . Therefore , in general , limited spectral range up to 2 . 6 lm was used in the pres - ent study to avoid the effect of the thermal emission of the surface and low signal - to - noise ratio of the detector . However , since some aqueous minerals such as hydrous silicates and carbonates also have diagnostic absorptions between the ran"
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    • "Recently, Mumma et al. (2009) reported that a notable enrichment of methane was detected over several localized areas, including Syrtis Major and Nili Fossae regions, which correspond to areas where deep crustal carbonates have been found (Ehlmann et al., 2008; Michalski and Niles, 2010), although high levels of methane have not been confirmed by in situ measurement (Mahaffy et al., 2013; Webster et al., 2013). The presence of organic compounds have also been recognized in martian meteorites (Clemett et al., 1998; Becker et al., 1999; Sephton et al., 2002). "
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    • "Recently, carbonates have been detected at several sites on Mars, such as in the Nili Fossae region (Ehlmann et al. 2008), in the Columbia Hills of Gusev crater (Morris et al. 2010) and in Leighton crater (Michalski & Niles 2010). Carbonates have also been detected in Martian meteorite ALH84001, and have been thought to be of biological origin (McKay et al. 1996), however not without dispute (e.g. "
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