Lifting Odyssey on to its launch rocket

"The launch of 2001 Mars Odyssey represents a milestone in our exploration of Mars, the first launch in our restructured Mars Exploration Program we announced last October," said Ed Weiler, Nasa's Associate Administrator for Space Science.

"Mars continues to surprise us at every turn. We expect Odyssey to remove some of the uncertainties and help us plan where we must go with future missions," he added.

However, officials are keeping a close eye on increased solar activity, which could wreak havoc with Odyssey's delicate electronics systems and rocket boosters.

No confusion

Other than our Moon, Mars has attracted more spacecraft exploration attempts than any other planet.

A two-year survey looking for ice

Of the 30 missions sent to Mars by three countries over 40 years, fewer than one-third have been successful.

In 1999, Mars Climate Observer and the Mars Polar Lander were both lost as they arrived at the Red Planet due to embarrassing errors involving inadequate testing and confusion between metric and English unit measurements.

Nasa scientists are determined that it will not happen again.

George Pace, Mars Odyssey project manager, said: "We haven't been satisfied with just fixing the problems from the previous missions. We've been trying to anticipate and prevent other things that could jeopardise the success of the mission."

'Virtual shovel'

Odyssey is part of a long-term robotic exploration initiative. "The scientific trajectory of the restructured Mars Exploration Program begins a new era of reconnaissance with the Mars Odyssey orbiter," said Dr Jim Garvin of Nasa's Mars Exploration Program.

Ultimately, the spacecraft could contribute significantly toward a more sophisticated exploration of Mars...perhaps an eventual human visit

George Pace, Odyssey project manager

"Odyssey will help identify and ultimately target those places on Mars where future rovers and landers must visit to unravel the mysteries of the red planet," he said.

It will carry three scientific instruments to map the chemical and mineralogical make-up of Mars: a thermal-emission imaging system, a gamma ray spectrometer and a Martian radiation environment experiment.

The imaging system will map the planet with high-resolution thermal images and give scientists information about how the mineralogy of the planet relates to its landforms. Astronomers have said it will be like a "virtual shovel" digging into the surface.

Odyssey's gamma-ray spectrometer will allow scientists to peer into the shallow subsurface of the planet to measure many elements, including the amount of hydrogen.

Ground ice probe

Hydrogen is mostly likely present in the form of water-ice. Odyssey's spectrometer will therefore be able to find permanent ground ice and see how it changes with the seasons.

"For the first time at Mars, we will have a spacecraft that is equipped to find evidence for present near-surface water and to map mineral deposits from past water activity," said Dr Steve Saunders, Mars Odyssey project scientist.

"Despite the wealth of information from previous missions, exactly what Mars is made of is not fully known, so this mission will give us a basic understanding about the chemistry and mineralogy of the surface," he said.

"Ultimately, the spacecraft could contribute significantly toward understanding what may be necessary for a more sophisticated exploration of Mars, and perhaps an eventual human visit," said George Pace.