Second Mars rover starts exploring and taking pictures

The Nasa rover Opportunity has made tracks across the vast grey plain where it landed on Mars, driving down the front ramp of its landing pad until its three pairs of wheels touched the planet's surface.

The rover then aimed its onboard cameras for a last look back at the spacecraft that cushioned its crash landing on the Meridiani Planum near the planet's equator seven days ago.

Opportunity's 3m jaunt at 9.30pm on Saturday (NZ time) marks the first time that two mobile robots have simultaneously explored another planet.

Opportunity's twin, Spirit, landed on the other side of Mars on January 3 and began exploring the enormous Gusev Crater for signs of ancient water 12 days later.

A crowd of engineers and scientists - some fresh off 12-hour shifts piloting Spirit - whooped and clapped as the images confirming Opportunity's successful egress reached them at Nasa's Jet Propulsion Laboratory in Pasadena yesterday via the Mars orbiter Odyssey.

"We're two for two! One dozen wheels on the soil," flight director Chris Lewicki announced to the packed control room.

The photos taken by the rover's hazard and navigation cameras showed two straight, rough tracks in the powdery surface leading away from the empty lander.

"That was probably the scariest part of the drive we're going to have on Mars," said the mission manager, James Erickson.

The next couple of Martian days, or sols, will be devoted to calibrating the scientific instruments on Opportunity's robotic arm.

The rover will then use the arm to test and photograph the soil in the small crater where it landed.

Today, Spirit is expected to resume scientific duties that were interrupted on January 22 when the rover's computer memory malfunctioned and it stopped communicating with Nasa.

Software engineers last week apparently solved the rover's problems by deleting a large number of files from its flash memory, which may have become overloaded, and rebooting it.

The rover was poised with its robotic arm extended, preparing to grind the surface of a football-shaped rock nicknamed Adirondack, when it short-circuited.

Over the next few days, Spirit is expected to complete its examination of Adirondack, which data showed is a volcanic basaltic rock of a type common on Earth.

Scientists said Spirit then would make its way towards a crater nicknamed Bonneville about 250m away, taking time to investigate two nearby whitish rocks dubbed Cake and Blanco.

The golf cart-sized Spirit and Opportunity are each equipped with a mobile laboratory of geologic tools designed to search for evidence that the barren Martian surface was once wetter, and possibly more hospitable to life, than it is now.

Opportunity sits at the centre of a crater that is 22m across and 3m deep and is covered with gray granules containing hematite, a mineral that on Earth forms in the presence of iron-rich water.

Infrared scans show that the concentration of hematite appears strongest near an outcrop of bedrock about 8m northwest of the lander, said mission scientist Phil Christensen.

Scientists have pointed to the outcrop as a likely first destination for Opportunity, because they believe the pale, exposed bedrocks hold clues to the Red Planet's geologic and climatic past.

- REUTERS