On May 25, 2011 NASA finally pulled the plug on one of the world's greatest Mars explorers, the rover Spirit. The six-wheeled robot landed on Jan. 3, 2004 on the Red Planet and was expected to last about three months so NASA definitely got its money worth out of the little guy.
Here's a quick tour of some of the biggest discoveries and accomplishments made by Spirit. Here's one of the first looks sent back to Earth by Spirit a day after it landed. Note its air bags in this image.