NASA engineers were prepared to cut the rover Spirit loose from its lander overnight in preparation for its first venture across the Martian landscape this week.
A guillotine blade, driven by a small explosive charge, was to slice through the final cable linking the rover to its landing platform.
Then, sometime late tomorrow or early Thursday, if all goes well, the desk-size scooter will turn 115 degrees on its six wheels and roll down one of the lander's ramps onto the desolate surface of the red planet.
Scientists engineered the tricky maneuver after one of the lander's airbags failed to fully deflate and retract, partly blocking the primary off-ramp.
Spirit, one of twin Mars rovers launched last summer, landed Jan. 3. The second, Opportunity, is scheduled to bounce down on the other side of the planet Jan. 25.
The $820 million dual mission is the first to land successfully on Mars since 1997.
Spirit's roll-off will be a dramatic moment for mission personnel. "I've been waiting for this for about three years," said Kevin Burke, lead engineer for the rover's move.
Geologists on the mission team say they plan to move the rover no more than 10 yards from the lander at first, stopping to analyze soil and rocks.
"After that, it gets very difficult to project into the future," said geologist John Grotzinger, a science team member from the Massachusetts Institute of Technology. "The immediate long-term goal is to move toward the crater 250 meters away," dubbed Sleepy Hollow. Eventually, scientists may try to explore a range of hills east of the landing site.
The latest images from the spacecraft include a 360-degree panorama of its landing site. It reveals a rusty brown landscape dotted by rocks and broken by sandy depressions. Rolling hills in the distance and sharp rocks in the foreground lie under a pale, tan sky.
"You don't have enough time to go to all the places that are very exciting," said science team member Michael Malin.
The local geography, he said, appears to be the result of eons of meteorite impacts that gouged craters and tossed up mounds of ejecta. "We're not looking at pristine, original surface out there," Malin said.
One close-up image showed odd, mudlike patches where the lander's retracting airbags scraped across the pebbly Martian soil. Portions of the dirt appeared to stick together, bunch and even roll up like a rug. Team members immediately named it the "magic carpet."
The strange cohesive behavior of the Martian dust was reminiscent of mud or damp clay, prompting speculation that there might be water in the soil. The possible existence of water on Mars is a key question the landers are seeking to resolve.
But Malin said the planet's cold temperatures and low air pressure would rapidly remove any water in surface soils.
"Very, very fine-grained material behaves in unusual ways," he said. "If you look at the footprints of the Apollo astronauts [on the moon], they formed these really crisp, vertically walled sole marks. Very fine materials in the absence of water are capable of doing some very strange things."
Grotzinger said electrostatic charges in the soil might also explain the odd cohesion.
Malin said he believes that water and regular freeze-thaw cycles may have played a role in creating many of the fractured rocks around the lander. In any case, he said, scientists are "itching" to get the rover moving to take a closer look with Spirit's microscopic imager.
Spirit remained healthy as it prepared to hit the dirt, officials said. It's producing all the electricity it needs and communicating "extremely well" with controllers, 110 million miles away on Earth.
Inside its electronics compartments, they said, the rover is running "a bit toasty" at 115 degrees Fahrenheit. Scientists believe it will cool down once it gets moving and changes its position relative to the sun.
On the outside, however, it's mighty cold in the Gusev Crater. The surface temperature warms to about 15 degrees Fahrenheit at 2 p.m., said Joy Crisp, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Overnight lows plummet to minus 100 degrees, she said, equivalent to "an exceptionally cold night on the South Pole."