Just watched a program on Nova/PBS from 2005 Called "Welcome to Mars" It depicted the Spirit and Opportunity landings and investigations.
They did prove that water was on the surface, unfortunatley it was sulphuric acid. There would have been no such thing as "clean" water and any liquids extracted would have be very hard to get clean water out of the mixture. You would also be left with a high percentage of Sulfate Salts, which is what the surface of mars has for bedrock, large rocks made of volcanic rock with little round BB size spheres of Sulphate salts.
They called them blueberries in the show. Unfortunaltey the show is a pay to see kind of thing unless you can catch the broadcast as I did. I am looking into moreinformation on the NOVA/PBS site as they have a ton of Mars info from all the landers.
I did however find the written transcript for the episode,
http://www.pbs.org/wgbh/nova/transcripts/3201_mars.html, dry reading, but good if you are looking for a basis for the science of the game.