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Increased European participation and new technical approaches are set to revitalize US plans for exploring Mars, which had been showing signs of becoming stalled by cost overruns and engineering difficulties, according to US officials. The new approach will transform NASA's plans for the exploration of Mars into a fully-fledged joint venture with overseas partners, say the officials.

Sparkling again: international study group is bringing fresh impetus to plans for Mars missions. Credit: MALIN SPACE SCIENCE SYSTEMS

NASA's decision in late spring to drop a long-distance rover from its planned 2001 Mars mission signalled that the agency's strategy to visit the planet roughly every two years and begin collecting samples in 2001 was starting to unravel. The rover had been designed to wander up to 100 kilometres from its landing site, gathering rock samples for return to Earth. But engineering development problems with the vehicle led to severe cost overruns that threatened to break NASA's $200 million-a-year Mars budget.

Now a far less capable rover is likely to fly on the mission, and no samples will be collected. Dropping the long-distance rover was a “considerable disappointment,” says Michael Carr, a planetary scientist with the US Geological Survey in Flagstaff, Arizona.

This and other signs of trouble prompted NASA science managers to call for a fresh look at the long-term strategy for Mars exploration. A team of 30 engineers, planetary scientists, biologists and other specialists led by Charles Elachi of the Jet Propulsion Laboratory (JPL), California, has been meeting during the summer, and hopes by early September to produce a new draft “architecture” for Mars exploration. Louis Friedman, director of the California-based Planetary Society, says the group has “a lot of clever people coming up with a lot of clever ways of doing things”. As a result, he says, the Mars programme is “sparkling again”.

Part of the reason is a growing European involvement with the programme. Elachi's team includes representatives from France, Italy and the European Space Agency (ESA). They bring engineering and scientific expertise, and the promise of financial resources beyond what the White House and US Congress have been willing to provide. Dan McCleese, chief scientist for Mars exploration at JPL, calls this a “significant new step”.

“We had, up until this study, a NASA-only programme,” McCleese says. “Now we've decided to build this [new] architecture assuming international cooperation.” Key to the plan would be France's provision of an Ariane 5 launch for the sample return mission in 2005, as well as a Mars-orbiting spacecraft that would receive samples from the surface (see Nature 391, 213; 1998).

The Italian Space Agency is proposing a communications satellite in Mars orbit to collect data from other spacecraft and relay them to Earth. ESA's proposed Mars Express mission, which hopes for a final go-ahead from the agency's Science Programme Committee in November and a launch in 2003, will carry an Italian-US radar system for detecting water beneath the surface of Mars.

France will also provide free ‘piggyback' launches on Ariane, which can deliver additional small payloads (30 to 40 kilograms) to Mars at regular intervals. Elachi says these small missions — as many as four for every two-year launch opportunity — are likely to be an integral part of NASA's new plan as they could scout out sites for subsequent landers. By 2015 samples could be collected from up to six different locations on Mars.

One innovation that holds great promise is a recent proposal by JPL engineers to launch samples from the Martian surface to Mars orbit using solid-fuel rockets rather than heavier and more complicated liquid-fuel rockets. If approved, the technique could dramatically reduce costs or allow more scientific equipment to be sent to Mars.

The Elachi team will not deliver its final report until late September, but scientists who have been involved in the discussions are enthusiastic about the results so far. Steven Squyres of Cornell University, whose experiments on the 2001 mission had to be scaled down because of the loss of the more capable rover, says: “I'm feeling more optimistic about this programme than I have in years.”