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The cumulative data from Curiosity since its arrival on Mars three and a half years ago shows that the lake that once filled Gale Crater lake had had a stratified chemical make-up.
Previous work had revealed the presence of a lake more than three billion years ago in Mars’ Gale Crater. This study defines the chemical conditions that existed in the lake and uses Curiosity’s powerful payload to determine that the lake was stratified. Stratified bodies of water exhibit sharp chemical or physical differences between deep water and shallow water. In Gale’s lake, the shallow water was richer in oxidants than deeper water was.
“These were very different, co-existing environments in the same lake,” said Joel Hurowitz of Stony Brook University, Stony Brook, New York, lead author of a report of the findings in the June 2 edition of the journal Science. “This type of oxidant stratification is a common feature of lakes on Earth, and now we’ve found it on Mars. The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive, including those that thrive in oxidant-rich conditions, those that thrive in oxidant-poor conditions, and those that inhabit the interface between those settings.”
While what Hurowitz says above is true, remember that this discovery provides zero evidence of past life on Mars. All it has done is teach us something about the different conditions in the lake at different depths.