KENNEDY SPACE CENTER, FLA. - The Mobile Service Tower is rolled back at Launch Complex 17A to reveal a Delta II rocket ready to launch the Mars Exploration Rover-A mission. NASA's twin Mars Exploration Rovers are designed to study the history of water on Mars. These robotic geologists are equipped with a robotic arm, a drilling tool, three spectrometers, and four pairs of cameras that allow them to have a human-like, 3D view of the terrain. Each rover could travel as far as 100 meters in one day to act as Mars scientists' eyes and hands, exploring an environment where humans are not yet able to go. MER-A, with the rover Spirit aboard, is scheduled to launch on June 8 at 2:06 p.m. EDT, with two launch opportunities each day during a launch period that closes on June 24.