Last week, NASA announced with much fanfare that Opportunity had found evidence that the region of Mars was once drenched with water. But it turns out, NASA's other rover, Spirit, has found quietly evidence as well, but using completely different clues. The rover found cracks inside a rock dubbed "Humphrey", which look like they are minerals crystallized out of water. The amount of water that could create this is far less than the amount that acted on Opportunity's landing site, demonstrating that Mars probably had a diverse climate in the past.