Today marks the third anniversary of the Mars rover Spirit landing safely, with Opportunity’s anniversary coming up in just a couple of weeks, and the accomplishments of the Mars Exploration Rover Mission in that time are astonishing. Not only have they kept two robots running on the surface of a distant planet years longer than planned, but they’ve continued to use them to collect valuable data. The rovers have recently had their programming updated again to allow new functionality, including new recognition algorithms based on what we’ve been able to learn about the surface of Mars so far and what scientists now think they are looking for. To celebrate the anniversary, NASA is sponsoring a Photo Contest on their site asking visitors to vote on their favorite image collected from the rovers from the past three years – you should definitely head over and check them out, especially the final image of a sunset over Mars – beautiful!