Page last updated at 23:42 GMT, Thursday, 29 May 2008 00:42 UK

Mars lander flexes its robot arm

Mars Reconnaissance Orbiter image of Phoenix lander on the Martian surface (Nasa/JPL-Caltech/University of Arizona)
A Nasa orbiter took this image of Phoenix on the surface of Mars

Nasa's Mars lander Phoenix has unstowed its robotic arm - the key tool in its mission to test the red planet's soil for the building blocks of life.

The 2.35m (7.7ft)-long titanium and aluminium extension will dig below the Martian topsoil to the water-ice which is thought to lie just beneath.

The next step will be to test the arm's four joints to be sure it is in working order before digging into the soil.

Phoenix touched down successfully on Mars' northern plains on 25 May (GMT).

Matt Robinson, from Nasa's Jet Propulsion Laboratory (JPL) in California, said: "Yesterday we sent commands... down to the lander to unstow the arm, and today I am ecstatic to let you know that it was successful.

"The robotic arm is now unstowed, it's out of its launch restraints."

After a health check that tests the robotic appendage at a range of warmer and colder temperatures, a camera on the arm will be used to look under the spacecraft to assess the terrain and underside of the lander.

Infographic, BBC
Phoenix carries seven science instruments

The robotic arm will later dig into the icy layers of Mars' northern polar region and deliver samples of both soil and ice to instruments on the lander's deck for analysis.

Phoenix is set to investigate the planet's geological history and search for the chemical building blocks which could support life.

The spacecraft has also transmitted a 360-degree panorama of its frigid Martian environment.

"We've imaged the entire landing site, all 360 degrees of it. We see it all," said the mission's chief scientist Peter Smith, from the University of Arizona, Tucson.

"You can see the lander in a fish-eye view that goes all the way out to the entire horizon. We are now making plans for where to dig first, and what we'll save for later."

Phoenix is an apt name for the current mission, as it rose from the ashes of two previous failures.

In September 1999, the Mars Climate Orbiter spacecraft crashed into the red planet following a navigation error caused when technicians mixed up "English" (imperial) and metric units.

A few months later, another Nasa spacecraft, the Mars Polar Lander (MPL), was lost near the planet's South Pole.

Phoenix uses hardware from an identical twin of MPL, the Mars Surveyor 2001 Lander, which was cancelled following the two consecutive failures.

The probe was launched on 4 August 2007 on a Delta II rocket from Cape Canaveral Air Force Station in Florida.

Landing sites
Phoenix landed further north than previous missions

Mars lander is 'in good health'
27 May 08 |  Science/Nature
In pictures: Mars landing
26 May 08 |  In Pictures
Phoenix diary: Mission to Mars
26 May 08 |  Science/Nature
Mars probe set for risky descent
14 May 08 |  Science/Nature
The long quest for life on Mars
06 Feb 08 |  Science/Nature

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