It was once
wet at Meridiani Planum.
Rocks are a
mixture of chemical and siliciclastic sediments with a complex diagenetic history.
Uppermost
strata are water-lain; lowest strata have
undergone eolian reworking.
Environmental conditions recorded include episodic inundation by shallow surface water, evaporation and desiccation.
Conditions were habitable, but could have posed significant challenges to the origin of
life:
Highly saline?
Highly acidic?
Arid and only intermittently wet?
Aqueous
precipitates (particularly concretions) might be good at preserving fossil evidence of microbial life.