Mars Science Laboratory Observations of Chloride Salts in Gale Crater, Mars

Abstract

The Mars Science Laboratory Curiosity rover is traversing a sequence of stratified sedimentary rocks in Gale crater that contain varied eolian, fluviodeltaic, and lake deposits, with phyllosilicates, iron oxides, and sulfate salts. Here, we report the chloride salt distribution along the rover traverse. Chlorine is detected at low levels (<3 wt.%) in soil and rock targets with multiple MSL instruments. Isolated fine‐scale observations of high chlorine (up to ≥15 wt.% Cl), detected using the ChemCam instrument, are associated with elevated Na2O and interpreted as halite grains or cements in bedrock. Halite is also interpreted at the margins of veins and in nodular, altered textures. We have not detected halite in obvious evaporitic layers. Instead, its scattered distribution indicates that chlorides emplaced earlier in particular members of the Murray formation were remobilized and reprecipitated by later groundwaters within Murray formation mudstones and in diagenetic veins and nodules.

An interval of high salinity in ancient Gale crater lake on Mars

“…At Old Soaker, Ca-sulfate enrichment occurs in sandstone adjacent to the mudcracks (Figure 3-d). Second, elevated concentration of Na-chloride in the bedrock is also observed, relative to stratigraphically lower strata 31 . Na-chloride occurrences in specific intervals, close to sulfate enrichments suggests remobilization from layers potentially enriched in halite (Figure 1-e).…”

“…Location of Old Soaker 34 and other candidate desiccation cracks ( Figure S13). e, Average normalized Cl peak area associated with halite detections ( Figure S10) 31 , error bar represents the uncertainty of the average. where euhedral white crystals ( Figure S4-g) and heterogeneous Ca-sulfate and Mg-sulfate enrichments were observed (mcam08733).…”

“…These late Ca-sulfate fluids were likely to have partially mobilized highly soluble salts within the bedrock such as halite. Indeed enhanced Na-chloride detections occur at specific stratigraphic intervals(Figure 1-e,Figure S10), and their sporadic distribution in bedrock and occasionally in association with fracture-filling Ca-sulfates indicate remobilization31 . Locally, lateral variation and possible cross-cutting of Mg-sulfate enrichment occurs at a cm-dm scale (Figure S7), as well as sporadic detections of Mg-sulfate nearby the stratigraphic succession(Figure 1-d), may also reflect localized dissolution and reprecipitation of initial deposits.…”

Can Halophilic and Psychrophilic Microorganisms Modify the Freezing/Melting Curve of Cold Salty Solutions? Implications for Mars Habitability

“…T he presence of liquid water on Mars has been linked to a decrease in the freezing point of aqueous solutions by variable enrichment in dissolved salts such that high ionic solutions and brines would be prevalent on a ''cool and wet'' Mars (Fairén, 2010(Fairén, , 2020, a hypothesis that has found recent support in the identification of highly saline intervals in the Gale crater lakes (Rapin et al, 2019;Thomas et al, 2019). Perchlorate salts are of particular relevance to Mars.…”

Hydrogeochemical Study on Closed-Basin Lakes in Cold and Semi-Arid Climates of the Valley of the Gobi Lakes, Mongolia: Implications for Hydrology and Water Chemistry of Paleolakes on Mars

“…Theoretical studies suggest the possibility that chlorides in paleolakes would have been provided through inflow of groundwater that interacted with subsurface rocks [8]; however, an alternative possibility of accumulation of pre-existing salt deposits to paleolakes via near-surface water flows cannot be ruled out [8]. Chloride and sulfate salts have been also found in lacustrine sediments of Gale Crater [15,16]. Although their occurrences indicate evaporative concentrations of early Gale lakes [16], the sources of dissolved species in the lake water remain uncertain.…”