Initially planned to function for three months, the Spirit rover has been in service for six years as of 3 January. Currently, however, Spirit is stuck in a sand pit with little hope of escaping its location.
With two malfunctioning wheels, NASA needs to tilt Spirit so its solar panels can catch sunlight in the upcoming Martian winter. If this fails, the rover will freeze to death as it will no longer be able power its internal heaters.
Even if the rover remains stuck, NASA hopes to continue research with it functioning as a stationary probe until dust covers the solar panels and it can no longer generate power.