NASA's Opportunity and Spirit rovers touched down on Mars in 2004 for a planned 90-day tour; six years and a few serious snags
later, the latter of the two is facing its death of cold. Since March 22, 2010, Spirit's been slumbering on the surface -- stuck and unable to generate enough power to communicate -- and while internal heaters and a favorable position on a sun-facing slope allowed the rover to survive previous Martian winters, this time the chances aren't so good. "The rover is experiencing the coldest temperatures it's ever been in – equivalent to about minus 55 degrees Celsius," NASA told Space.com
. Should Spirit wake up next year, it will resume a stationary mission to help scientists determine whether Mars has a liquid core, but if not there's always the chance it might
spontaneously regain power
still find utility in another decade or four
. Still not on the docket: ever returning home.