It's been more than nine years, but the Mars rover Opportunity just made a discovery that ranks among its biggest. The rover has discovered rock in the Endeavour Crater that's full of what appear to be clay minerals—suggesting it had extended contact with water, the BBC reports. Despite talk of water, "what Opportunity has mostly discovered, or found evidence for, was sulfuric acid," says a NASA rep. But "clay minerals only tend to form at a more neutral pH. This is water you could drink."
That points to intriguing possibilities: "This is water that was much more favorable for things like pre-biotic chemistry—the kind of chemistry that could lead to the origin of life," says the NASA spokesman. "The fundamental conditions that we believe to be necessary for life were met here," he notes, per Space.com. It's not the first time Opportunity has found clay in the area—but the rock, called Esperance, has the highest concentrations the rover has seen. Opportunity, which landed in 2004, wasn't expected to last this long. "The rover could have a catastrophic failure at any moment. So, each day is a gift," says another NASA spokesman. (Read more Mars rover stories.)