Mars Science Lab, nicknamed "Curiosity," is a $2.5 billion nuclear-powered rover that is about size of a compact car - about twice as long and three times heavier than NASA's predecessor Mars rovers, Spirit and Opportunity.
Curiosity is expected to touch down on Aug. 6, 2012, inside a 96-mile-wide impact crater called Gale Crater to scout for chemicals and geologic environments that may have been suited for life.
Update: 9:15 a.m.
The Atlas rocket has been fueled and all remains on schedule for launch at 10:02 a.m. EST. So far, the weather appears to be cooperating.
Image: Mars Science Lab's rocket ride to space, an Atlas 5 booster, is poised for blastoff at 10:02 a.m. EST Saturday from Cape Canaveral Air Force Station in Florida. Credit: United Launch Alliance.
Update: 9:58 a.m.
Launch team has cleared the rocket for blastoff at 10:02