The launch took place at 1:58 p.m. EDT (1758 GMT) in Cape Canaveral, Florida, after bad weather has forced US space agency NASA to postpone the liftoff for two consecutive days.

The robot rover, named Spirit by a 9-year-old girl in Arizona, the United States, will arrive at Mars in January, 2004, and operate for at least three months. Its identical twin, called Opportunity, is scheduled to be launched on June 25.

"The instrumentation onboard these rovers, combined with their great mobility, will offer a totally new view of Mars, including a microscopic view inside rocks for the first time," Dr. Ed Weiler, associate administrator for space science at NASA, said in a statement.

The two rovers will bounce to airbag-cushioned landings at the opposite side of Mars. At a height of about 1.5 meters, each rover carries five scientific instruments and can work as a robot field geologist, self-driving across the Martian surface, navigating itself around obstacles and examining rocks and soil for clues about water and life.

The designated landing site for the rover Spirit is Gusev Crater, which appears to have been a lake in the past, according to Dr. Joy Crisp, a project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

Recent observations by spacecraft orbiting Mars indicated that there was water on the planet in the past, but scientists hope to find out how long water existed in Mars and whether it could sustain the existence of life.

The two rovers, at a total cost of US$800 million, are a new test for NASA as the world's largest space agency is trying to reestablish its credibility after the failure of two Mars probes four years ago and the loss of space shuttle Columbia early this year.

(Xinhua News Agency June 11, 2003)