Compositional investigation of the proposed chloride‐bearing materials on Mars using near‐infrared orbital data from OMEGA/MEx

Abstract

1] Several hundred occurrences of chloride-bearing salt deposits have been proposed in terrains within the southern highlands of Mars on the basis of Thermal Emission Imaging System and Thermal Emission Spectrometer infrared observations. The spectral identification of chloride salts by remote sensing is challenging because they are transparent over much of the thermal infrared portion of the spectrum. Further ambiguity arises from the diverse geologic settings in which the putative chloride-bearing materials are found. In order to better constrain the composition of these unique compositional units, we perform a global survey of these materials in the Near-Infrared (NIR) domain with the Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) imaging spectrometer. The spectral signatures of the deposits are consistent withalthough not specific ofchlorides. We do not observe olivine to be associated with the deposits, which confirms that sulfides are an unlikely alternative candidate. Our systematic search reveals the global lack of association with hydrated minerals (phyllosilicates, sulfates, hydrated silica) except for a few deposits (noteworthy in northwestern Terra Sirenum) where a small fraction of chloride material overlaps Fe/Mg-rich clay-bearing terrains. Even in these locations, the morphology and crosscutting relationships of the deposits suggest two separate episodes of mineralization, first phyllosilicates then chlorides, followed by subsequent formation of sulfates. Our study shows that local groundwater upwelling seems to be the most frequent source for the water involved in the formation of chloride, rather than surface runoff.

Analysis of polygonal cracking patterns in chloride‐bearing terrains on Mars: Indicators of ancient playa settings

“…This hypothesis appears contradictory to previous conclusions by other studies [ Glotch et al ., ; Ruesch et al ., , section 2]. For instance, Ruesch et al .…”

“…For instance, Ruesch et al . [] analyzed the mineralogical compositions in the chloride‐bearing terrains using data from the OMEGA imaging spectrometer. One of their conclusions was the lack of association of chlorides with hydrated minerals globally (e.g., phyllosilicates, sulfates, and hydrated silica).…”

A revised Pitzer model for low-temperature soluble salt assemblages at the Phoenix site, Mars

“…Orbital spectra and in situ measurements by rovers have identified a variety of salts on Mars, including chlorides (Osterloo et al, 2008;Ruesch et al, 2012), sulfates (Gendrin et al, 2005;Langevin et al, 2005;Murchie et al, 2009;Bish et al, 2013), and carbonates (Bandfield et al, 2003;Ehlmann et al, 2008;Morris et al, 2010;Niles et al, 2013). Perchlorates have also been measured in soils by the Wet Chemistry Laboratory (WCL) experiment on the Phoenix Lander , and elsewhere by pyrolysis experiments on the Curiosity Rover (Leshin et al, 2013;Ming et al, 2013) (Navarro-González et al, 2010).…”

Visible‐near‐infrared reflectance spectroscopy of volcanic acid‐sulfate alteration in Nicaragua: Analogs for early Mars

“…Exposures of alunite, jarosite, gypsum, Mg/Fe sulfates, Al phyllosilicates, Fe/Mg phyllosilicates, and chlorides have been observed in this area [Glotch et al, 2010;Wray et al, 2011;Ruesch et al, 2012]. In particular, alunite has been observed in association with silica-rich material and Al phyllosilicates at Cross crater [Swayze et al, 2008].…”