Blocked ramp delays Spirit rover’s roll-out on Mars

THE Spirit rover will spend another week parked on the spacecraft that took it to Mars, as cautious engineers work to clear a safe path for the six-wheeled robot to roll off and begin prospecting its rocky surroundings, NASA officials said.

Further complicating the mission, new images from the spacecraft suggest its landing site is not the pristine dry lake bed scientists originally had hoped.

That implies the robotic explorer's hunt for geologic evidence that the planet once was a wetter place conducive to life might be more difficult than expected.

The earliest Spirit will roll on to Mars is January 14 three days later than originally planned. Further delays remain possible.

That has made mission members eager to get Spirit rolling even more anxious.

"We are champing at the bit to get this puppy off the lander and get driving," said Art Thompson, tactical uplink lead for the 650 million double mission.

The Mars Exploration Rover project includes a second, identical rover. That rover, Opportunity, is scheduled to arrive on Mars on January 24.

The Spirit delay gives engineers time to further retract portions of the now-deflated air bags that cushioned the golf cart-sized rover's landing. Two sections of the air bag partially block the ramp that mission members want the rover to follow.

"As soon as we get that air bag out of the way, we're good to go," said Arthur Amador, mission manager.

Ground control will learn today if Spirit's attempt to perform a "lift and tuck operation" to raise the blocked ramp and further draw in the bits of deflated air bag has been successful.

If it fails, Spirit can roll down either of two other ramps.

Those manoeuvres would require the rover to perform a robotic pirouette, however, to ensure it faced the right direction.

Spirit continues to do science work from its perch above the Martian surface. Scientists have received the first data from Spirit's mini-thermal emissions spectrometer, which determines mineralogical composition of rocks and soils it views.

Scientists picked Spirit's landing site inside Gusev Crater because they believed the depression once contained a brimming lake the type of place that may have been hospitable to life. If that was the case, Spirit should be seeing a flat plain rich in fine-grained sediments, said Ray Arvidson, of Washington University, and the mission's deputy principal scientist.

"That's not what we're looking at," he said.

Spirit's first look suggests if the landing site was ever a lake bed, it has been significantly altered by other geologic processes. What they might have been remains the subject of intense debate among mission scientists.

Mr Arvidson speculated that a volcanic eruption could have buried the dried lake bed with lava, which subsequent impacts by asteroids or comets then fragmented. Later, deposits carried by wind, water or even ice glaciers might have further buried the area with the rocky debris that Spirit's cameras show in detail.

"The question is going to be how far we have to go and what we have to do to find a smoking gun" that would prove Mars once was a wetter world, Mr Arvidson said.