An unmanned Delta rocket blasted off from Cape Canaveral Air Force Station early on Saturday, sending a water-analysing science probe on its way to Mars.
The Phoenix spacecraft, which lifted of at 5:26 am EDT, is expected to reach the northern polar region of Mars on May 25.
"It's a wonderful morning to go to Mars," Phoenix project manager Barry Goldstein, with NASA's Jet Propulsion Laboratory in Pasadena, California, said during the televised commentary shortly before liftoff.
Upon reaching Mars, Phoenix will use a heat shield, parachutes and thruster rockets to gently lower itself onto frozen soil, which is believed to cover a thick layer of water ice. The probe's robotic arm is about 7 1/2 feet long (2.3 metre) has a 7.7-foot-long robotic arm, equipped with a drill and other instruments, to bore down into the ground and retrieve soil and ice samples for analysis.
The work will be done within the body of the lander. Phoenix's lab includes eight ovens to bake samples so that a gas sniffer can detect vaporized gases.
The experiment should tell scientists several things about Mars' water, including whether it once was liquid and whether it contains any organic molecules. Both conditions would substantially increase the chances that Mars was suitable for life to develop.
Unlike the Viking missions of the mid-1970s, Phoenix's goal is not to search for life directly but rather to ascertain if the conditions on Mars were or are suitable for indigenous microbial life to take root.