NASA sends robot probe in search of life on Mars

WASHINGTON (AFP) - A US space probe embarked on a 10 month journey to Mars, where it will dig through Martian soil in a search for signs of life in a frigid region of the Red Planet.

The Phoenix Mars Lander separated from a Delta II rocket after blasting off into the dark sky at 5:36 am (0936 GMT) from the Kennedy Space Center in Cape Canaveral, Florida.

Powered by solar panels, Phoenix, whose launch was delayed by one day following bad weather, is scheduled to land on Mars on May 25, 2008, after traveling 680 million kilometers through space.

The National Aeronautics and Space Administration hopes to land the probe on flat ground with few or no rocks at a Martian latitude equivalent to northern Alaska on Earth.

During its three-month mission, the lander will pierce through soil in the planet's arctic region amid freezing temperatures ranging from minus 73 degrees Celsius to minus 33 C.

The craft is equipped with a 2.35 meter (7.5 foot) robotic arm that will enter vertically into the soil to break the icy crust believed to lie within a few inches of the surface.

The robotic arm will lift samples onto the lander's deck and use instruments to check for water and carbon-based chemicals, considered essential building blocks for life, and analyze the soil chemistry to look for clues of past or present life.

With its two solar panels deployed, the lander, built by US aerospace firm Lockheed Martin, measures 5.5 by 1.5 meters (18 by five feet), weighs 350 kilograms (770 pounds) and carries 55 kilograms (121 pounds) of scientific equipment.

"Our instruments are specially designed to find evidence for periodic melting of the ice and to assess whether this large region represents a habitable environment for Martian microbes," said Phoenix investigator Peter Smith of the University of Arizona, Tucson.

Phoenix also has a weather station that will measure water and dust content in the planet's atmosphere.

Many scientists see signs of ancient rivers and oceans on the arid and sterile surface of Mars, and believe the planet may once have harbored some forms of life.

In 2002, the NASA probe Mars Odyssey detected huge quantities of hydrogen on the Martian surface, a sign there could be ice at a depth of less than one meter (three feet).

NASA's roving robots Spirit and Opportunity have also found signs of past water flows while rolling across the Martian landscape since 2004.

Unlike the rovers, the 420-million-dollar Phoenix lander will stay put in one location during its mission. It will also have a softer arrival on Mars than the rovers, which made a bouncy landing inside huge air bags.

As with previous missions, Phoenix will deploy a heat shield to slow its high-speed entry into the Martian atmosphere. It will then open a supersonic parachute that will cut its speed to about 217 kilometers (135 miles) per hour.

The lander then separates from the parachute and fires pulsed descent rockets to slow the craft to about nine kilometers per hour (5.5 miles per hour) before landing on its three legs.

Fifteen minutes after landing, the probe's solar panels will deploy and power up its instruments.

But landing on Mars has been a fifty-fifty proposition for past missions to the Red Planet: half of the 14 missions sent by Russian, Japanese, American and European space agencies since 1988 have failed.