The Phoenix has been sending back photos from the planet's north pole that show signs of there being ice under the surface. The probe is equipped with a robotic arm, which is designed to dig below the frozen surface for samples of ice and water.

The director of NASA's jet propulsion laboratory, Dr Charles Elachi, has praised the efforts of the scientists behind the mission. "Many people thought that this will not be possible that we will not be able to succeed," he said.

"All of us knew this is very risky mission, but this thing made history and they will be remembered forever that they are the first people to explore the polar region of Mars.  "There is no telling what discoveries we'll be seeing over the next 90 days."

NASA's Mars exploration program manager, Fuk Li, has told ABC local radio the first photos show signs of there being ice under the surface.  "It's a very, very flat surface. There are small rocks, pebbles lying around," he said.

"It is like a permafrost region of the earth and the area is has polygonal kind of patterns on it, and we can see those with the images that we have obtained so far."

NASA's Opportunity rover is showing its age. Problems have forced the agency to suspend work involving the rover's rock grinding tool and its infrared spectrometer while engineers try to work out a fix.

The problems are the latest in a long line of failures that have begun to plague both rovers as they age.

Opportunity and its twin, Spirit, were designed to last just 90 days. But they have been driving around the Red Planet for nearly 4 years, having landed in January 2004.

The rovers' lifetimes were originally expected to be limited by dust accumulating on the panels. If dust reduced harvestable solar power too much, the rovers would have trouble keeping their electronic innards warm enough to survive the cold Martian nights, especially in the winter.

But gusts of wind have cleaned off both rovers' solar panels from time to time, allowing them to weather the coldest nights, says project manager John Callas of NASA's Jet Propulsion Laboratory in Pasadena, California, US.

Because of these helpful winds, Callas says he thinks the rovers will be limited more by how long their components can last against wear and tear.

The Martian surface will be explored for conditions favourable for past or present life thanks to micro-machine technology supplied by Imperial College London. The NASA mission, planned for August 2007, represents the first chance for UK hardware to contribute to the exploration of Mars since the failed Beagle 2 spacecraft launched in 2003

Dr Tom Pike and his team at Imperial's Department of Electrical and Electronic Engineering have provided substrates--surfaces used to hold samples for imaging--for the Mars Phoenix mission. These substrates will hold dust and soil for examination in a microscope station attached to the Phoenix lander.

The grains of Martian dust and soil, delivered by a mechanical excavating arm, will be imaged by an optical microscope and an atomic force microscope. Together they will provide the highest resolution of imaging ever taken on another planet.

"Nobody has looked at Mars at this type of resolution. It is very difficult to predict what we might find, but if you wanted to look for the earliest forms of past or present life we will be the first to look closely enough," said Dr Pike.

The team has been conducting trials on a replica of Phoenix's microscope station based at Imperial. They have been using the equipment for several months to work out the best way of studying the Martian soil.

They also visited Mission Control at the University of Arizona Tucson USA (14--20 July 2007). As part of the "operational readiness" process Dr Pike and his colleagues spent a week going through a simulation of the actual mission.

SYDNEY: Probes designed to find life on Mars do not drill deep enough to find dormant living cells, according to a new British study.

"Finding hints that life once existed - proteins, DNA fragments or fossils - would be a major discovery in itself, but the Holy Grail for astrobiologists is finding a living cell that we can warm up, feed nutrients and reawaken for studying," said lead author Lewis Dartnell, of University College London. 

According to the researchers, current drills may find tell-tale fragments that life once existed on Mars in the distant past. Finding 'reawakenable' cellular life, however, would require new technology to enable drilling many metres below the surface - beyond the reach of the solar radiation that pummels the Red Planet's surface.