Here is our pick of forty-two of the best pictures from the Mars Exploration Rovers (MER) mission.

NASA's MER-A (Spirit) rover successfully landed on January 3, 2004 in Gusev Crater, believed once to have been a crater lake.

A second rover, MER-B (Opportunity) landed on January 24, 2004 in Meridiani Planum.

Spirit and Opportunity have revealed geologic formations never before seen, and have confirmed that Mars had at least one salty sea in the distant past.

The rovers are still active, and mission funding has been extended to September 2006, and perhaps longer.

When you buy the "Rovers on Mars" screensaver, you will get the "MER Spacecraft 3D" screensaver absolutely FREE.

See the cruise-configuration spacecraft that delivered the rovers to the surface of Mars.