The first robot was scheduled for lift-off from Cape Canaveral aboard a Delta II rocket on June 5 between 1816 and 1855 GMT, while the second was due to be launched on June 25 between 0438 and 0519 GMT.

The first Rover has already been tested and was expected to be moved to a launch pad on May 27, according to the National Aeronautics and Space Administration.

NASA has decided to postpone the launch of the first robot, initially scheduled for May 30, because of an electrical problem which has since been repaired.

The problem was caused by a device allowing the Rover to cut cables linking it to a stage of the Delta II rocket during the last phase of the flight.

The first robot will try to land inside Mars's Gusev crater, south of the Red Planet's equator. The second will aim for the Planum meridian, which is known for its deposits of iron oxide.

SPACE.WIRE