NASA scientists said it took four years of analysis to determine there were high concentrations of carbonate in the rocks Spirit examined during late 2005. Carbonate originates in wet, near-neutral conditions, but dissolves in acid. The ancient water indicated by the find was not acidic.
"This is one of the most significant findings by the rovers," said Steve Squyres of Cornell University, the principal investigator for the two Mars rovers, Spirit and Opportunity. "A substantial carbonate deposit in a Mars outcrop tells us that conditions that could have been quite favorable for life were present at one time in that place."
The findings appear in the early online edition of the journal Science.