BTW, Philip!...
...a 40-60 Millibar martian atmosphere [4 Gyears ago?] would have had sufficient density/pressure to allow for lakes or seas of salty or acidic water to exist, ice or on ice, in the Meridiani Planum region of Mars for quite a long time...Conservative/cautious hypothesis? Certainly!... But good enough to get the imagination going.
Martian microbes anyone?
