The US space agency (Nasa) has finally succeeded in getting its second Mars Exploration Rover up and away on its six-month journey to the Red Planet.
The Opportunity vehicle took off from Cape Canaveral, Florida, at 2318 local time (0318 GMT).
Opportunity finally gets away
(Image by Boeing/Bailie)
It had been held on the launch pad because of a mixture of bad weather and concerns about insulation panelling on its rocket, a Boeing-built Delta II.
And an attempt on Sunday had to be called off because of the failure of a battery cell associated with a component of the launch vehicle's flight termination system.
Opportunity separated successfully from the Delta's third stage 83 minutes into its flight, after it had been boosted out of Earth orbit and on to a course towards Mars.
Flight controllers received a signal from the rover probe to report all systems on the space craft were operating normally.
"We have a major step behind us now," said Pete Theisinger, project manager. "There are still high-risk parts of this mission ahead of us, but we have two space craft on the way to Mars, and that's wonderful."
The long queue
Opportunity is built to roam the rocky surface of Mars for three months.
Opportunity's twin rover, named Spirit, blasted off from Florida on 10 June and is now hurtling through space towards Mars at a speed of more than 30 kilometres per second.
Spirit is 77 million kilometres from Earth. Eight days in front of the US rover is the European Mars Express mission with its Beagle 2 lander.
And currently third in the train is Nozomi, a Japanese probe that swung by Earth two weeks ago to pick up the final gravitational slingshot it needed to make it to the fourth planet.
All the probes, including Opportunity, will arrive at their destination at the end of 2003 or early 2004.
The twin rovers will act as robotic geologists. During their exploration of Mars, the vehicles will trundle up to 40 metres a day, looking for interesting rocks and soils.
Each is equipped with a panoramic camera, a camera for close-ups of rocks and a drill to cut into rocks. The data will be transmitted back to Earth.
The rovers are seeking chemical signatures that would confirm that abundant water once existed on the planet's surface.
Opportunity is aimed at a site called Meridiani Planum. It is a location known to have large deposits of grey hematite, a mineral that usually forms in a wet environment.
Spirit is going to Gusev Crater, which may once have held a lake.
Only three Nasa space craft have ever touched down successfully on Mars before: the Viking landers of 1976 and Mars Pathfinder.
Like the Pathfinder mission, the rovers will get down to the surface via parachutes; the final impact will be cushioned by gas-filled bags that will bounce across the terrain.