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 Na ₂O 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.

Key Points

• Isolated Cl enrichments in bedrock, in nodular textures, and at calcium sulfate vein margins, correlated with Na, indicate halite

• Mapping of Cl along the Curiosity traverse in Gale Crater indicates Cl enrichments are more common in select Murray formation members

• The scattered, isolated occurrences of chlorides are consistent with late groundwater reworking and remobilization of original deposits