Are we sure it's not just Spirit's tears?
http://xkcd.com/695/
Old-school Mars rover Opportunity has found "clear evidence" of water in the first four months of tootling around the rim of the Endeavour Crater. A vein of calcium, sulphur and gypsum. Credit: NASA/JPL-Caltech/Cornell/ASU A vein of calcium, sulphur and gypsum. Credit: NASA/JPL-Caltech/Cornell/ASU The crater is around four …
When estimating the longevity of these missions, I'm sure the engineers must follow Scotty's repair estimation philosophy (although in reverse!)...
Kirk: How much refit time before we can take her out again?
Scotty: Eight weeks, sir... but ya don't have eight weeks, so I'll do it for ya in two.
Kirk: Mr. Scott. Have you always multiplied your repair estimates by a factor of four?
Scotty: Certainly, sir. How else can I keep my reputation as a miracle worker?