Opportunity Still Producing

Lately, most of the attention given to NASA's Mars rovers has gone to the big new kid on the planet, Curiosity.  However, the older, smaller Opportunity is also still producing.

In fact, Opportunity has recently made what could be its biggest discovery yet.  It has found clay that formed in interaction with low pH water-- essentially, water we could drink.  That's another strong piece of evidence that Mars was habitable within its first bilion years.  So far, there's no firm evidence of Martian life, but if life ever arose on Mars, it could have had a nice long run.