The U.S. roving vehicle on Mars will not dip its wheels into the red planet's soil as soon as scientists had hoped. Engineers are delaying its expedition a few days while they work out some minor technical problems.
Mission scientists like Ray Arvidson of Washington University in St. Louis are eager to roll the Spirit rover off the lander in search of proof the barren Mars once had liquid water and could have been hospitable to life.
'We're ready to go," he said. "I mean, we're ready to get down in the dirt, in the rocks, and make measurements."
But engineers at the Jet Propulsion Laboratory in California are delaying the rover's move until at least next Wednesday - three days later than planned.
Airbags that had cushioned Spirit's landing are taking longer to retract beneath the rover than expected. Engineers want them out of the way when the robot descends the lander's ramp. In addition, they continue to study an intermittent power surge in the rover's high-data-rate antenna.
Mission technician Art Thompson says the team is being cautious.
"We might have a day that's just so good that we can actually get ahead of the schedule, but at this point, I wouldn't plan on us getting off before Wednesday, and I would not be surprised at all to come back and tell you that it's a day or two or more later," he said.
In the meantime, the Mars rover continues to transmit images of the surrounding terrain with two different cameras. Mission scientists are combining them to produce two mosaic panoramas. One set will be a high resolution, three-dimensional version of the color image released Tuesday. This will help scientists determine the size and distance of features. The other image set will portray the same panorama in infrared light to determine the mineral composition of rocks from afar. The pictures will give researchers a better idea of where to explore once the rover is unleashed.
When that occurs, however, the robot vehicle will plod cautiously and stay close to home base for a while before roaming further afield.
"It's clear that very close to the lander we want to stop and drop," said Ray Arvidson. "... that is, drop the instruments down onto the soil and make measurements that have never been done before on a planetary surface. So there's a lot to do in the immediate vicinity of the lander just to characterize what's there."
The Mars science team hopes eventually to advance the rover toward - and perhaps even reach - a range of hills they believe is one or two kilometers south of the lander.
The Spirit spacecraft touched down in Gusev Crater, a 150-kilometer wide equatorial area depression named for the 19th century Russian asrtronomer Matvei Gusev. It is thought to have been an ancient lakebed, but Ray Arvidson says upon closer inspection, it looks more like a rock-strewn plain than a typical lakebed.
"A lakebed is typically flat with very fine grain sediments," he said. "That's not what we're looking at. If there are lake sediments there, they've been chewed up and rocks have been brought in either from the bottom or laterally by some set of processes. Our job is to find the evidence as to whether or not in fact there were lake environments in the past there."
In two and a half weeks, an identical spacecraft named Opportunity is to land on the other side of Mars to inspect a smooth plane also suspected of being a water site long ago.