Abundance of minerals in the phyllosilicate-rich units on Mars

Abstract

Context. Phyllosilicates were definitely identified on Mars by the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) instrument onboard the Mars Express spacecraft. The identification, characterization, and mapping of deposits of these minerals hold clues to the potential past habitability. They also constitute a key element in planning for future landing sites. Aims. To infer the environmental conditions that existed at the time of the formation of these minerals, it is critical to determine if and how the composition of the deposits vary in space and time.Methods. We applied radiative transfer modeling to the OMEGA reflectance spectra to derive the modal mineralogy (mineral abundances) of some phyllosilicate-rich deposits. Results. In many outcrops, including the large areas in Nili Fossae, the surface mineralogy is dominated by primary non-altered minerals, with minor fractions of phyllosilicates. These assemblages could result from hydrothermal alteration. By contrast, deposits in the Mawrth Vallis region exhibit a large content of hydrated phyllosilicates, which suggests that the rocks may be mature sedimentary rocks or altered volcanics. Evidence of alteration resulting from metamorphism due to an impact is reported in the central peak of a crater.

Composition and thermal inertia of the Mawrth Vallis region of Mars from TES and THEMIS data

“…17). This possibility is contradicted by recent results which suggest from spectral modeling of OMEGA data that the altered rocks in the Mawrth Vallis region contain 30-60% clay minerals (Poulet et al, 2008). However, interpretation of absolute mineral abundances from remote sensing data requires consideration of the spatial resolution of the datasets.…”

Soil Diversity and Hydration as Observed by ChemCam at Gale Crater, Mars

“…Analyses of martian meteorites gave detailed information on the composition of the martian crust and interior (23). The composition of the martian surface was also estimated indirectly from its mineralogical characterization (24)(25)(26), but the cross section for very fine particles in these observations is often inordinately small. These investigations covered very different spatial scales, but no in situ information on martian soil chemistry was available at the subcentimeter scale (in areal extent), except for its volatile inventory in organic and volatile inorganic compounds by the Viking and Phoenix landers (~100-mg samples were analyzed by the Viking Molecular Analysis Experiment) (27,28).…”

“…Determining the level of regolith-atmosphere exchange of H 2 O, and thus its SSA, is also important to understand why the D/H ratio of soils, measured by SAM, is close to atmospheric values (26). Estimates of the SSA of the martian soil can be deduced from ChemCam day/night experiment results (see Materials and Methods).…”

A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology

“…The abundance and distribution of water on the martian surface throughout its history has also been inferred from the mapping of phyllosilicates Poulet et al, 2005Poulet et al, , 2008aPoulet et al, , 2008bLoizeau et al, 2007;Bishop et al, 2008;Combe et al, 2008;Ehlmann et al, 2008aEhlmann et al, , 2009Mustard et al, 2008;Marzo et al, 2009;Wray et al, 2009aWray et al, , 2009bCarter et al, 2010;Fairén et al, 2010); serpentines (Ehlmann et al, 2010); opaline silica-rich deposits (Bandfield, 2008;Milliken et al, 2008;Squyres et al, 2008;Rice et al, 2010), such as the recent discovery of extensive hydrated and poorly crystalline silica materials in the western Hellas Basin (Bandfield et al, 2013); carbonates (Ehlmann et al, 2008b;Boynton et al, 2009;Michalski and Niles, 2010;Morris et al, 2010); and other minerals characteristic of evaporites, such as sulfates Langevin et al, 2005;Fishbaugh et al, 2007;Mangold et al, 2008). Clay minerals are found almost exclusively in Noachian and early Hesperian terrains and are exposed to our view due to cratering in ejecta or within gullies found on the interior slopes of the crater walls, and in some cases within the sediments of craters (Wray et al, 2009a).…”