Mars' newest resident awoke to its first Red Planet dawn on Sunday, as NASA scientists back on Earth pored over scores of photos the Spirit rover sent back shortly after landing.

The craft landed 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 maneuver the rover.

Scientists were jubilant over the success on a planet where two of every three lander missions have produced nothing but space junk.

"It's a big step forward for all humanity. Now we have another rover on another planet, exploring a new world. What more could you ask?" said Charles Elachi, director of the National Aeronautics and Space Administration's Jet Propulsion Laboratory.

Rover gets a wake-up call

The first set of black-and-white photos were snapped by Spirit before darkness fell on the frigid martian surface and were relayed to Earth by the passing Odyssey orbiter. They show a flat, wind-scoured plain peppered with small rocks.

The scene enthused scientists, eager to send the rover prospecting among the rocks for evidence that the landing site once was covered with water.

"Home, sweet home," said Steve Squyres, the mission's main scientist. "This is our new neighborhood ... We hit the sweet spot."

Spirit settled into a "sleep" mode with the martian sunset, but sprang to life briefly overnight to transmit additional pictures and other data during two more satellite passes, one by the Mars Global Surveyor and another by Odyssey.

At about 2:42 pm PT (5:42 pm EST), a short time after sunrise on Mars, lab managers reactivated the rover, playing the Beatles song "Good Morning, Good Morning" in the control room to mark the occasion.

Scientist said their principal task during Spirit's first full day on Mars will be to extend the craft’s main antenna and point it toward Earth to establish a direct communications link with the robotic probe.

They also expect the rover to begin taking higher-resolution color photos that will be sent to Earth as early as Sunday night, providing panoramas of the martian surface in unprecedented detail and depth of field.

For now, the six-wheeled rover will remain folded up on its landing pad while mission controllers continue to run checks on its various systems and instruments. In the next day or two, the Jet Propulsion Laboratory team will lift the rover up off its belly and extend its front wheels, mission manager Jennifer Trosper said.

Scientists said it would be eight or nine days before the rover is ready to roll off on its three-month mobile mission.

One early concern abated as closer examination of what had initially appeared to be a large rock standing in the rover's path revealed the object was probably just part of a partially inflated air bag from the craft's landing.

'Great place to drive'

NASA targeted Spirit to land within a cigar-shaped ellipse just south of the Martian equator. Based on three grainy photographs taken by the spacecraft as it plummeted to the surface, navigators believed they delivered Spirit to within six miles of its intended target. Brian Portock, of the mission's navigation team, compared the feat to teeing off from Los Angeles and making a birdie in New York.

Over the next three months, the robot should use a suite of instruments to look for geologic evidence of past water activity in the rocks and soil. If water once filled Gusev Crater, it may have been a place suitable for life.

The terrain surrounding Spirit appeared scattered with small rocks, none larger than about a foot high, Squyres said. The trio of descent images showed the tracks of dust devils thought to frequently scour the area, sweeping it of the rusty grit that coats the planet.

Small pits -- sand traps, really -- filled with fine-grained material could be made out in the near distance. Rocks appeared abundant, but small enough to allow Spirit to roam unimpeded.

"It's a great place to drive," Squyres said.

Just west of the rover, scientists believed they could make out a craterlike depression rimmed by a small mesa that appeared to show ancient rock. Previous Mars missions never have investigated such a feature.

Squyres called it a "tantalizing" feature to explore, but first it must be determined whether it can be done safely. The depression might be full of soft dust that could mire the craft.

"I don’t know for sure it’s not a rover trap," he said.

It was a little warmer than expected -- about 98 below zero Fahrenheit -- possibly from heat-trapping dust in the atmosphere.

That meant the solar arrays were generating only 83 percent of the power expected, said Jennifer Trosper, Spirit's mission manager for surface operations. That could force mission managers to conserve power.

Major Mars missions, 1964 to 2004:

1964 US launches Mariner 3, which fails after liftoff.

1964 US launches Mariner 4. First successful Mars fly-by in July 1965. The craft returns the first pictures of the Martian surface.

1964 Soviets launch Zond 2. Mars fly-by. Contact lost in May 1965.

1969 US launches Mariner 6 and 7. The two spacecraft fly by Mars in July and August 1969 and send back images and data.

1971 Soviets launch Mars 2. Orbiter and lander reach Mars in November 1971. Lander crashes but orbiter sends back images and data.

1971 US launches Mariner 8, which fails during liftoff.

1971 US launches Mariner 9. Orbiter reaches Mars in November 1971, provides global mapping of Martian surface and studies atmosphere.

1973 Soviets launch Mars 5. Orbiter reaches Mars in February 1974 and collects data.

1975 US launches Viking 1 and Viking 2. The two orbiter/lander sets reach Mars in 1976. Orbiters image Martian surface. Landers send back images and take surface samples.

1992 US launches Mars Observer. Contact lost with orbiter in August 1993, three days before scheduled insertion into Martian orbit.

1996 US launches Mars Global Surveyor. Orbiter reaches Mars in September 1997 and maps the planet. Still in operation.

1996 Soviets launch Mars 96, which fails after launch and falls back into Earth's atmosphere.

1996 US launches Mars Pathfinder. Lander and rover arrive on Mars in July 1997, in the most-watched space event ever. Lander sends back thousands of images, and Sojourner rover roams the surface, sending back 550 images.

1998 Japan launches Nozomi. Orbiter suffers glitch in December 1998, forcing circuitous course correction. Mission fails in 2003.

1998 US launches Mars Climate Orbiter. Spacecraft destroyed while entering Martian orbit in September 1999.

1999 US launches Mars Polar Lander. Contact lost with lander during descent in December 1999. Two microprobes "hitchhiking" on lander also fail.

2001 US launches Mars Odyssey. Orbiter reaches Mars in October 2001 to detect water and shallow buried ice and study the environment. It can also act as a communications relay for future Mars landers.

2003 European Space Agency launches Mars Express. Orbiter and lander to arrive at Mars in December 2003.

2003 US launches Mars Expedition Rovers. Spirit and Opportunity rovers due to land on Mars in January 2004.

(China Daily January 5, 2004)