The Boeing-built Delta II rocket carrying the Spirit -- which encloses the Mars Expedition Rover A (MER-A), the first of two robots that will closely study the red planet -- launched Tuesday at 1:58 pm (1758 GMT).

A camera mounted on the rocket showed images of its flight path above the Florida coast, then the upper strata of the atmosphere at speeds of more than 15,000 kilometers (9,300 miles) per hour.

The spacecraft is to traverse some 500 million kilometers (300 million miles) over seven months, then drop into the Gusev crater, 15 degrees south of the Martian equator, in early January 2004.

Two robots, MER-A and MER-B, are to be sent to Mars.

The second, MER-B, is scheduled for launch on June 25 and to land on January 25, 2004 in an area of Mars known as the Meridiani Planum.

The aim of the mission is to find water which would indicate that there could have been life or that life was possible.

"This will continue NASA's long goal of finding the water. On Earth, wherever we find water, we find life," Ed Weiler, associate administrator for space science for NASA said earlier this week.

"There was water on Mars billions of years ago and maybe just a few hours ago."

The US space agency, which has chalked up two costly failures in its quest to explore Mars in recent years, warned that the task would not be easy.

"It's not a trip to the beach on a Sunday afternoon," Weiler said.

"We can have a bad day on Mars. Wind. Bad weather. We are trying to predict the weather on Mars for January 2004."

Of 30 attempted Mars missions over the past 40 years, just 12 have succeeded, Weiler noted.

Bad weather has already delayed the probe's launch since late last week, at which point its landing on Mars was scheduled for January 4.

SPACE.WIRE