Thrilled by the apparently flawless landing of the Spirit rover on Mars (search), NASA scientists pored over photos and other information Sunday, awaited a stream of even more tantalizing data and worked on the days-long process of getting the robot ready to roll.

Spirit made a nerve-racking but safe landing on Mars late Saturday on what scientists believe is the rocky bed of an ancient lake that once may have harbored life.

Just three hours later, the six-wheeled rover began zipping the first black-and-white images of its surroundings to Earth, 106 million miles distant at the time. 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 (search) Jet Propulsion Laboratory.

The first images from Spirit 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."

NASA said Spirit's first color images could be transmitted to Earth early Monday, relayed by a second spacecraft in orbit around the Red Planet.

Meanwhile, mission members worked to pinpoint where Spirit made its apparently flawless landing.

"Sometimes it's good to be lucky," Squyres said.

The $820 million NASA Mars Exploration Rover (search) project also includes a twin golf cart-sized rover, Opportunity. That robot is set to reach the opposite side of Mars from its sibling on Jan. 24.

The dozens of initial, low-resolution photos show Spirit landed upright, level and facing south on a flat stretch of Gusev Crater. Scientists believe the Connecticut-sized basin once contained a brimming lake.

As early as Monday, Spirit could be told to raise itself up — a two-day process — and extend its front legs. It will take nine to 10 days before the six-wheeled robot is ready to roll off its lander and begin roaming Mars.

There were a few minor concerns about the mission. Scientists were trying to determine whether a dark object lodged against one corner of the lander was a rock that might block the rover once it's ready to roll onto the ground. On Sunday, mission members said the object could be a dirty piece of one of the air bags that cushioned the rover's landing.

Engineers spent Sunday trying to reposition Spirit's lollipop-shaped high-gain antenna, which is blocked by the rover's own camera mast. The rover was designed to use the antenna to communicate directly with Earth.

Spirit's successful landing bucked a trend of failed missions to Mars. Just one in every three past attempts to land on the planet has succeeded. British scientists said Sunday they would keep trying to contact their probe, the Beagle 2, which was supposed to land on Mars on Christmas.

NASA's last attempt to land on Mars, in 1999, ended in failure. Its last successful landing was in 1997, when Pathfinder carried the tiny Sojourner rover to the surface of Mars.

The Spirit rover also spent a chunk of Sunday sleeping — its systems powered down — until its solar arrays had drawn enough energy from the sun to wake it later in the day.

Scientists planned to play the Beatles' "Good Morning, Good Morning" before communicating with Spirit, Squyres said.

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.