The Mars Exploration Rover 2 MER 2 sits on the base petal of the lander while workers check the placement.

The Mars Exploration Rover 2 (MER-2) sits on the base petal of the lander while workers check the placement. Set to launch in Spring 2003, the MER Mission consists of two identical rovers. Landing at different regions of Mars, they are designed to cover roughly 110 yards each Martian day over various terrain. Each rover will carry five scientific instruments that will allow it to search for evidence of liquid water that may have been present in the planet's past. The first rover has a launch window opening May 30, and the second rover a window opening June 25.