Before or after the dynamo loss?
With results from Mars Express, Jean-Pierre Bibring gave us a brilliant speech about Mars history. It's Mars Express findings that help locate the selected landing site for MSL.
It has to do with what happened to Mars before and after it lost its magnetic field. I'm not going to look for more info now (not that easy to use the PC in a hotel room), but the chances of finding liquid water are not as big as we thought they would be, before ME made its analysis.