The National Aeronautics and Space Administration has slated the next attempt at blastoff for Wednesday July 2 following the fresh failure on Sunday to launch the probe.

The space agency had already called off a launch scheduled just after midnight Saturday due to high winds at Cape Canaveral.

"The launch is further postponed to Wednesday, July 2, by problems with the cork insulation on the Delta launch vehicle," NASA spokesman George Diller said.

A fresh attempt will be made at 11:17 pm Wednesday (0317 GMT Thursday), with a second potential launch window shortly afterwards at 11:50 pm.

Opportunity is waiting to follow its twin, the Mars Expedition Rover "Spirit," which was launched June 10 and is scheduled to land in early January 2004 in the Gusev Crater, 15 degrees south of the equator of Mars.

Opportunity is likewise bound for a seven-month journey through space. Its touchdown target, 491 million kilometers (305 million miles) away, is the Meridiani Planum, a zone containing a concentration of ferrous oxide situated two degrees south of Mars' equator.

Although both probes will set down relatively close to the Martian equator, they will be on virtually opposite sides of the planet, some 6,000 miles (9,600 kilometers) apart.

NASA is investing some 800 million dollars on the two six-wheeled vehicles, which for three months are to probe sites thought to be geologically important, roaming in search of clues of how long water flowed on the Martian surface.

"These missions are not designed to find life on Mars," NASA associate administrator Ed Weiler told a press conference Friday. "They are not designed to find water on Mars. They are designed to answer a critical question in the search for life.

"We know Mars has water, we know it had it in the past and may have it in the present," he said. "What we don't know is how long the water persisted in any given place.

"If it stayed there for tens of millions of years, then there is a good chance that life might have evolved. Because on Earth, wherever we find water and energy and organic compounds, we find life, no matter what the conditions are."

The European Space Agency also has a probe -- "Mars Express" -- bound for Mars and scheduled to arrive next January.

"We look at this as an opportunity to join forces as two major space agencies and share data and the public excitement," Weiler said.

"It would be great to have three landers on Mars at once. So far, I haven't detected any sense of competition. Ultimately, if we send humans to Mars, I have the feeling it's going to be an international effort so we've got to learn how to work together and I think we are doing that here."

SPACE.WIRE