US rover calls home, beams back colour photos

The US robotic probe Spirit beamed panoramic colour images of unprecedented clarity back to earth yesterday after establishing direct contact with Nasa scientists guiding its search for ancient signs of life on Mars.

The successful deployment of the rover's lollipop-shaped main antenna cuts the delay in communications between the rover and Nasa's Jet Propulsion Laboratory in Pasadena to about nine minutes from the hours needed to relay signals through two Mars orbiters, flight director Jason Willis said.

At 9.20 p.m. PST (0520 GMT Monday), the control room at JPL erupted in cheers as test signals showed that the rover had correctly located earth in the martian sky and had positioned the main, "high gain" antenna correctly.

"This is just fantastic. We got the high gain antenna to work on the very first try," Mark Adler, Spirit mission manager, said. "We are ready for the rest of the mission."

Spirit began transmitting science and telemetry data, as well as the mission's first colour images of the martian landscape from the rover's high-resolution panoramic cameras.

"I expect to see a lot of good stuff on this pass," Mr Adler said, adding that scientists planned to "wake up" the rover four or five times during the night to calibrate temperature sensors that may have failed.

The mission fell behind on Sunday as scientists ran out of time to cut cables that tied the folded-up rover to battery and electronics systems on its landing pad, an omission that may delay its three-stage "stand-up" by one martian day, or "sol", about 40 minutes longer than an earth day, Mr Adler said.

The team also may try to retract airbags that cushioned the rover's landing but now block its path to the planet's surface, adding another sol to the time needed to prepare the robotic rover for its three-month trek across Mars' surface to look for ancient evidence of life-giving water in the rocks and soil.

The rover's "stand-up" was scheduled for sols three through five, after more cables bolting the rover's wheels and robotic arm are cut by pyrotechnic blades, and its six wheels are moved to their correct positions, Mr Adler said.

Once the rover is freed, scientists will "do a little drive" on top of the lander and turn it to drive off the lander - about sol eight or nine.

The team of scientists and engineers that guided Spirit to a bouncy but textbook-perfect landing pored over data beamed back by the rover on Sunday to learn more about its descent, landing and exact position on the hostile planet.

The craft landed on Saturday night - mid-afternoon Mars time - almost exactly on target, at Gusev Crater, a massive basin the size of Connecticut that scientists believe may be the site of dry lake bed once fed by a long, deep martian river.

Besides being an ideal place to search for evidence of water, and possibly life, the landing zone is an area free of large boulders and thick accumulations of dust, making it easier to manoeuvre the rover.

"It's a lot flatter than I expected and a lot less rocky than I expected," geologist Wendy Calvin told reporters at an Sunday evening news conference.

Mission controllers said Spirit appeared to have come through its rough-and-tumble descent and touchdown in good working order. "All in all things performed pretty nominally and we are very satisfied," Prasun Desai, Nasa trajectory analyst, said.

Spirit is the fourth probe ever to successfully land on Mars, following in the footsteps of two Viking landers in the 1970s and the Pathfinder mission in 1997. Spirit's twin explorer, the rover Opportunity, is due to land on the opposite side of the planet on January 25.

Spirit's triumphant arrival on Saturday night, confirmed by a radio signal at 8.52 p.m. PST (0452 GMT), came after it plunged through the thin martian atmosphere tethered to a parachute, then bounced to the surface cushioned in a cluster of air bags. The landing climaxed a seven-month journey to the fourth planet from the sun - the second closest to earth after Venus.

Mars has proven a perilous destination. Nasa said more than half of man's missions to the red planet have ended in failure. Mars claimed two Nasa spacecraft in 1998 and 1999.

Nasa administrator Sean O'Keefe called the $820 million mission a "double-header" following the successful Stardust mission on Friday that intercepted a comet and gathered particles from its tail in a first that could offer clues about how earth began.

Missions to the Red Planet

The US spacecraft carrying a robotic explorer designed to search for signs of life on Mars, beamed images of the bleak Martian surface back to scientists on Earth on Saturday hours after its arrival on the red planet.

Missions to Mars began in the 1960s but two-thirds of them have been unsuccessful.

The following is a chronology of the main Mars missions:

November 28, 1964 - Mariner 4, US: First successful Mars fly-by in July 1965. The craft returned the first close-up photographs of the Martian surface.

November 30 - Zond 2, Soviet Union: Mars fly-by. Contact lost in May 1965.

May 19, 1971 - Mars 2, Soviet Union: Orbiter and Lander, reached Mars in November. Lander crashed but Orbiter sent back images and data.

May 30 - Mariner 9, US: Orbiter reached Mars in November, provided global mapping of Martian surface and studied atmosphere.

July 25, 1973 - Mars 5, Soviet Union: Orbiter reached Mars February 1974 and collected data.

August 20, 1975 - Viking 1, US: Orbiter and Lander reached Mars in June 1976. Orbiter imaged Martian surface. Lander sent back images and took surface samples.

September 25, 1992 - Mars Observer, US: Orbiter. Contact lost in August 1993, three days before scheduled entry into Martian orbit.

November 7, 1996 - Mars Global Surveyor, US: Orbiter reached Mars in September 1997 and began mapping the planet, showing signs of a huge chasm and a giant dust storm.

December 4 - Mars Pathfinder, US: Lander and Rover. Landed on Mars on July 4, 1997, in the most-watched space event. The lander sent back thousands of images. Its Sojourner Rover roamed the surface, sending back 550 images.

December 11, 1998 - Mars Climate Orbiter, US: Destroyed on entry in September 1999 because engineers had used two sets of measurements - one in miles and the other in kilometres.

April 7, 2001 - Odyssey, US: Arrived on Mars on October 24 to detect water and shallow buried ice and study the environment. It can also act as a communications relay for future Mars landers.

June 2, 2003 - The Mars Express: First fully European mission sent to any planet, carries Beagle 2, which will burrow into the Martian surface and study the atmosphere.

June 10 - Mars Expedition Rovers, US: A robot launched atop a Delta 2 rocket. Water is the sole objective of the mission. A second robot, the Mars Expedition Rover B, nicknamed Opportunity, is launched on July 7.

December 19: Beagle 2 parts from the Mars Express rocket.

December 25: Mission suffers setback after Beagle 2 fails to emit a call sign to show it has landed.

January 3, 2004: The US lander carrying the Spirit rover makes a textbook touch-down in a huge impact crater on Mars. The golf-cart-sized mobile geology laboratory will study the rocks and soil on Mars for evidence of water and past or present life.