Probe to make perilous landing on Mars

After a nine-month journey through space, the US probe Phoenix is about to land on the arctic surface of Mars to dig for ice in a new quest for signs of life on the Red Planet.

NASA's $US420 million ($A439.47 million) probe will become the first spacecraft to land on the Martian arctic surface and will stay there for a three-month mission.

After travelling 679 million kilometres through the cosmos, Phoenix will enter the top of the Martian atmosphere at around 2331 GMT Sunday (0931 Monday AEST), zipping in at 21,000km/h to begin a perilous descent that will end with a soft landing seven minutes later.

But the US space agency's Jet Propulsion Laboratory (JPL) in Pasadena, California, which controls the mission, will have to wait an agonising 15 minutes for the radio signal confirming the safe landing to reach Earth.

"This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky," said Ed Weiler, associate administrator for NASA's Science Mission Directorate.

"We do believe that it's a risk worth taking," said F.Li, manager of NASA's Mars Exploration program, "because I think that the science the mission will return with will be outstanding and we will open up a new chapter on how we understand Mars to be".

Since Mars exploration began in the 1970s, more than half, or 55 per cent, of probes sent to the Red Planet have failed to reach their destination.

Like previous Mars landers, Phoenix is equipped with a thermal shield to slow its entry into the atmosphere and will deploy a parachute to slow its speed.

The probe will then fire up its thrusters to slow its descent to 8km/h and land on its three legs on the circumpolar region known as Vastitas Borealis - akin to northern Canada in Earth latitude.

One minute after Phoenix confirms arrival, its radio will go silent for 20 minutes to save its batteries before deploying its two solar antennas.

The first images of Phoenix will reach Earth two hours later.

"The Phoenix mission not only studies the northern permafrost region, but takes the next step in Mars exploration by determining whether this region, which may encompass as much as 25 per cent of the Martian surface, is habitable (for future manned missions to Mars)," said Peter Smith, Phoenix principal investigator at the University of Arizona.

The probe will work under harsh conditions with temperatures ranging between minus 73 and minus 33 degrees Celsius.

NASA wants to assess whether the Martian Arctic ever had conditions favourable to microbial life. The probe will also help determine if a primitive life form was ever or is still present on Mars.

"The Arctic region is a place where there is a lot of things we are learning about the Earth," said Smith.

"One is the climate change for our planet is written into the ices in the Arctic region on the Earth," Smith said.

He added that the Arctic regions are "where the history of life" - microbes, molecules and cells - "is preserved in its purest form."

Researchers "are wondering if this is true on Mars".

Phoenix is equipped with a camera and a 2.35-metre robotic arm that can dig as deep as one metre to find ice and heat up samples to detect water.

The robot's instruments can detect carbon and hydrogen molecules, essential elements of life.

With its two solar panels unfurled, Phoenix is five metres wide and 1.52 metres long. It weighs 350kg, including 25kg of scientific instruments.

Phoenix will be latest ambitious mission to explore Mars.

The US Mars Odyssey orbiter detected vast quantities of hydrogen on the planet's surface in 2002, a sign that its polar regions are covered in ice.

The roving robots Spirit and Opportunity, which have roamed the Martian surface's equator for three years, have also discovered signs of past water.

http://au.news.yahoo.com/080523/2/16za5.html?f=mv