Light‐toned salty soils and coexisting Si‐rich species discovered by the Mars Exploration Rover Spirit in Columbia Hills

Abstract

[1] Light-toned soils were exposed, through serendipitous excavations by Spirit Rover wheels, at eight locations in the Columbia Hills. Their occurrences were grouped into four types on the basis of geomorphic settings. At three major exposures, the light-toned soils are hydrous and sulfate-rich. The spatial distributions of distinct types of salty soils vary substantially: with centimeter-scaled heterogeneities at Paso Robles, Dead Sea, Shredded, and Champagne-Penny, a well-mixed nature for light-toned soils occurring near and at the summit of Husband Hill, and relatively homogeneous distributions in the two layers at the Tyrone site. Aeolian, fumarolic, and hydrothermal fluid processes are suggested to be responsible for the deposition, transportation, and accumulation of these light-toned soils. In addition, a change in Pancam spectra of Tyrone yellowish soils was observed after being exposed to current Martian surface conditions for 175 sols. This change is interpreted to be caused by the dehydration of ferric sulfates on the basis of laboratory simulations and suggests a relative humidity gradient beneath the surface. Sirich nodules and soils were observed near the major exposures of S-rich soils. They possess a characteristic feature in Pancam visible near-infrared (Vis-NIR) spectra that may be diagnostic of hydrated species, and this spectral feature can be used to search for additional Si-rich species. The exposures of hydrated salty soils within various geomorphic settings imply the potential existence of hydrous minerals in similar settings over a much wider area. Hydrous sulfates represent one of the candidates that may contribute the high level of water equivalent hydrogen in equatorial regions detected by the Neutron Spectrometer on Mars Odyssey.Citation: Wang, A., et al. (2008), Light-toned salty soils and coexisting Si-rich species discovered by the Mars Exploration Rover Spirit in Columbia Hills,

Spectral properties of simulated impact glasses produced from martian soil analogue JSC Mars-1

“…The coarse fractions are dominated by basaltic glass, while the finest ones are dominated by the brighter weathering products. Exploration Rovers 2006;Rieder et al, 2004;Yen et al, 2005;Wang M A N U S C R I P T ACCEPTED MANUSCRIPT 16 et al, 2008;Ming et al, 2008). In general, the simulant closely matches typical Martian soils for in controlling the VNIR spectral properties of glasses produced from Fe-bearing samples.…”

Exchange and fractionation of Mg isotopes between epsomite and saturated MgSO4 solution

“…In contrast, carbonates may have been less important in the evaporite sequences on Mars, because evidence so far suggests that the sulfur cycle, instead of a carbon cycle, dominated surficial processes on ancient Mars (McLennan et al, 2007;Wang et al, 2009). The significance of Mg sulfates on the Martian surface (e.g., Wang et al, 2008) suggests that the Mg isotope compositions of evaporites from Mars would provide important constraints on the evaporative history of early Mars.…”

“…Magnesium sulfate is also present on the surface of Mars, where, for example, up to 36 wt.% sulfate has been found in some outcrops on the Martian surface, of which Mg sulfate is the most abundant (Clark et al, 2005). On the Martian surface, sulfates are a major water reservoir and thus it is inferred that at least at one point in time aqueous alteration occurred on parts of the Martian surface (e.g., Wang et al, 2008).…”

Volcanic hydrothermal systems as potential analogues of Martian sulphate-rich terrains

“…Acid hydrothermal leaching of basaltic rocks has also been proposed as the formation mechanism for opaline silica deposits in the Nili Patera caldera on the Syrtis Mayor volcanic complex (Skok et al, 2010). Additionally, APXS analysis of light-coloured soils by Spirit at Husband Hill (Gusev crater) revealed the combination of elevated SiO 2 contents and the presence of Fe and Mg sulphates at the sites of Paso Robles and Tyrone (Wang et al, 2008), indicating that these soils are probably formed by the interaction between rocks and fumarolic condensates derived from degassing magma and/or by oxidative alteration of crustal Fe-sulphide deposits . Amorphous silica and jarosite associations have also been identified by CRISM data on plateaus above Juventae Chasma (Milliken et al, 2008;Bishop et al, 2009), Melas Chasma (Metz et al, 2009) and Ophir Chasma (Wendt et al, 2011), where they have been interpreted as the product of acid alteration of basalts.…”