An Atlas 5 rocket blasted off from Cape Canaveral Air Force Station in Florida today to dispatch a sophisticated Nasa science probe on a journey to look for water on Mars.
After two days of delays due to minor technical concerns, the 57-metre Atlas 5 booster, built by Lockheed Martin, blasted off its seaside launch pad on time at 7.43am (12.43pm Irish time) and soared into clear skies over the Atlantic Ocean.
"What a difference a day makes," said Nasa launch manager Chuck Dovale.
"It couldn't have been any smoother."
Nestled in a protective cargo hold perched on the rocket's nose was the 2,180 kg Nasa Reconnaissance Orbiter, also built by Lockheed Martin.
The spacecraft's primary goal is to continue the search for evidence showing how long Mars had water, which scientists believe is key to learning if life ever existed on Mars.
When the satellite arrives in Mars seven months from now, it will join two other US orbiters, Mars Global Surveyor and Mars Odyssey, Europe's Mars Express spacecraft and the twin robot rovers, Spirit and Opportunity.
"Dramatic discoveries, about recent gullies, near-surface permafrost and ancient surface water have given us a new Mars in the past few years," said Michael Meyer, Mars exploration chief scientist at NASA headquarters in Washington, DC.
"Learning more about what has happened to the water will focus searches for possible Martian life, past or present."
The spacecraft is equipped with three high-resolution cameras and a radar sounder that can detect water and ice below Mars' surface. It is to spend four years in orbit around Mars looking for spots to land future rovers and eventual human expeditions.
Other instruments will be able to map surface minerals and monitor Mars' atmosphere.
The complement of cameras includes one with the largest-diameter telescopic lens ever sent to another planet. Scientists have high hopes the camera will be able to snap pictures showing details as small as the width of an office desk.
"Every time we look with increased resolution, Mars has said, 'Here's something you didn't expect. You don't understand me yet.' We're sure to find surprises," said project scientist Richard Zurek of NASA's Jet Propulsion Laboratory in Pasadena, California.
The craft, which is capable of transmitting data back to Earth 10 times faster than previous Mars probes, also is intended to serve as the communications relay station for a rover slated to launch in 2007 and a science laboratory targeted for launch in 2009.