Amid pessimism over the outlook for Spirit, the spacecraft's twin, Opportunity, was in a perfect trajectory meanwhile for a landing on the surface of the Red Planet this weekend, the National Aeronautics and Space Administration officials said.

Opportunity is to land at 9:05 pm Saturday (0505 GMT Sunday) on the Meridiani Planum, described by NASA as one of the "smoothest, flattest places on Mars."

Opportunity scientist Joy Crisp said that Meridiani "meets our criteria for a safe landing and is an excellent place for science."

Spirit landed on Mars on January 3 and had been functioning near-perfectly until Wednesday, beaming back to Earth spectacular color photographs of the surface of the Red Planet. But communications were abruptly cut off two days ago and only partially restored on Friday.

NASA officials expressed concern the problems could take weeks to sort out and may not ever be entirely resolved.

"The chances it will be perfect again are not good," Mars Exploration Rover project manager Pete Theisinger told reporters at NASA's Jet Propulsion Laboratory in Pasadena, California. "We have got a long way to go with the patient in intensive care.

"It is still in a critical state, but stable," he said. "We don't know what's broken and the consequences. The flight software is not working properly.

"We should expect that we will not be restoring functionality to Spirit for a significant amount of time, many days, perhaps a couple of weeks, even under the very best of circumstances," Theisinger said.

Spirit suffered a "very serious anomaly" and stopped normal transmissions on Wednesday, but a signal was received on Friday from the solar-powered rover by one of the giant antennas of the international Deep Space Network near Madrid, Spain.

"The flight team for NASA's Spirit received data from the rover in a communication session that began at 1326 Universal Time and lasted 20 minutes at a data rate of 120 bits per second," NASA said.

The transmission speed of 120 bits a second was well below the normal speed of 11,000 bits a second but even the weak signal was welcomed after two days of worrying silence punctuated by an occasional meaningless "beep."

NASA engineers plan to ask Spirit to provide further information about its condition in an effort to work out why the rover fell silent on its 19th day on the Red Planet.

The breakdown came just as the rover was to begin searching for signs that there may have been water on Mars that could have sustained life.

The 820-million-dollar Spirit and Opportunity project is the most ambitious ever to Mars and follows a number of failed voyages to the Red Planet, including a European mission whose demise was acknowledged on Friday.

The European Space Agency (ESA) said final efforts to coax a call from Europe's lost Martian lander Beagle 2 would take place this weekend, but the chances of success are negligible. The British-built mini-lab was due to have landed on December 25 but has failed to radio home.

Theories that the Red Planet was once awash with water received dramatic backing meanwhile from data relayed to Earth from Europe's unmanned spacecraft Mars Express.

First results from Mars Express sketched the vision of a planet whose surface was once sculpted by seas and glaciers and confirms indications its South Pole is capped by frozen water, ESA said.

The 300 Million Dollar Robot
NASA always knew that its pioneer explorers, Spirit and Opportunity, would be temperamental twins and that has been confirmed with the breakdown of the first of the robotic probes to venture onto Mars.

The agency's associate administrator for space science Ed Weiler warned 48 hours before the rocket carrying Spirit took off in June: "It's not a trip to the beach on a Sunday afternoon."

The six wheeled Mars Exploration Rovers are 1.6 metres (5.2 feet) long and has a 1.5 metres (4.9 feet) high camera mast that gives it the look of a golf buggy adapted for Star Wars.

Each is packed with sensitive equipment to search for signs that their may have been water on Mars in the past that could have sustained life.

The equipment includes a Miniature Thermal Emission Spectrometer from Arizona State University, a Mossbauer Spectrometer from Johannes Gutenberg University in Germany, an Alpha Particle X-ray Spectrometer from the Max Planck Institute for Chemistry in Germany and a Microscopic Imager from NASA's Jet Propulsion Laboratory in California, which is managing the whole 800-million-dollar project.

A rock abrasion tool, called a RAT, grinds on the rocks that have been found on the surface so they can be examined and data sent back to Earth. The spectrometers identify different minerals.

The panoramic 360 degree camera on the mast sent back the most spectacular colour and infra-red images of the surface ever seen.

The whole thing has been moved around by the six wheel drive buggy, which has a 'rocker bogie' suspension system which bends at its joints rather than using springs. This enables the rover to cross rocks bigger than the wheel diameter of 26 centimetres (10 inches).

The solar robotic explorers can trek up to 40 meters (about 44 yards) each Martian day.

Scientists were to command the vehicles to head for specific targets chosen from the images and date received each day.

But this has halted since NASA lost contact Wednesday with Spirit, the first of the two robotic probes, which landed on Mars on January 3.

The second, Opportunity, is due to land on another part of the planet this weekend. Each was intended to work for at least 90 martian days, which take the mission until late April.

Before the takeoff from Earth, NASA had delayed the launch because of a problem with its cables that could cause the robots to short-circuit.

Problems with the airbags that cushioned the January 3 landing held up the start of the exploration on the surface.

Related Links
Mars Rovers at JPL
Mars Rovers at Cornell
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only