An artist's concept depicts NASA's Phoenix Mars Lander a moment before its 2008 touchdown on the arctic plains of Mars. A US space probe named Phoenix Mars Lander has been successfully launched from Cape Canaveral, Florida, and began its nine-month journey to Mars, where it will dig for clues to past and present life. [Photo: AFP]

By Jean-Louis Santini

A US space probe named Phoenix Mars Lander was successfully launched early Saturday from Cape Canaveral, Florida, and began its nine-month journey to Mars, where it will dig for clues to past and present life.

The lander blasted off from Cape Canaveral, Florida, aboard a Delta II rocket at 5:36 am (0936 GMT) in a flawless launch that illuminated the dark night sky.

Phoenix had been originally scheduled to launch on Friday, but the mission was postponed 24 hours after bad weather Tuesday prevented fueling of the two-stage rocket.

If everything goes as planned, Phoenix should complete its 680 million kilometer (422 million mile) 420-million-dollar journey to Mars on May 25, 2008.

About 90 minutes after launch, the Delta II rocket will give the probe the final push it needs to send it from Earth orbit to Mars.

The lander's assignment is to dig through the Martian soil and ice in the arctic region and use its onboard scientific instruments to analyze the samples it retrieves.

"We have worked for four years to get to this point, so we are all very excited," said Phoenix project manager Barry Goldstein at NASA's Jet Propulsion Laboratory in Pasadena, California.

NASA hopes to land the probe on flat ground with few or no rocks at a Martian latitude equivalent to northern Alaska on Earth.

Phoenix is likely to face Martian temperatures that range from minus 73 degrees Celsius (minus 99 degrees Fahrenheit) to minus 33 C (minus 27 F).

Once it lands safely on the Martian surface, the probe will deploy a set of research tools never before used on the planet.

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

The Phoenix's robotic arm will lift soil samples to two instruments on its deck. One instrument will check for water and carbon-based chemicals, considered essential building blocks for life, while the other will analyze the soil chemistry.

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 likely sign there could be ice at a depth of less than one meter (three feet).

"Phoenix investigates the recent Odyssey discovery of near-surface ice in the northern plains on Mars," said Phoenix Principal Investigator Peter Smith of the University of Arizona, Tucson. "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."

Unlike NASA rovers Spirit and Opportunity, which have been rolling across the Martian landscape since 2004 powered by their solar batteries, Phoenix will stay in one place on the Martian ground.

And unlike the rovers, which made a bouncy landing on Mars inside huge air bags, Phoenix is programmed to carry out a soft touchdown.

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 rocket engines 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.

The Phoenix Mars Lander measures 5.5 by 1.5 meters (18 by five feet) and carries 55 kilograms (121 pounds) of scientific equipment.