The Mars Exploration Rovers (MER) are some of the most famous robotic explorers of our time. They were sent to Mars with a expected lifetime of only 90 sols (a Martin day, which is about 24.6 hours). They have been so successful and lucky that they are now on their fifth year. Opportunity is currently driving to Endeavor Crater. Meanwhile its twin, Spirit, is stuck.Spirit is currently on the west side of a feature called Home Plate. The intrepid rover can't seem to get traction in the soft dirt (called regolith). Some have speculated that Spirit may be stuck on top of a rock. At this point, the wheels are covered over the hub in regolith. While the engineers work on how to free the rover, the scientists aren't stopping.
The place Spirit got stuck is extremely interesting to scientists. Richard Moddis from NASA's Johnson team says "The exceptional amount of power available from cleaning of Spirit's solar arrays by the wind enables full use of all of the rover's science instruments. If your rover is going to get bogged down, it's nice to have it be at a location so scientifically interesting." The regolith surrounding the rover is tan, white, yellow, and dark red. By studying the regolith, scientists hope to get a better understanding of water's role in forming these deposits.
Source- NASA