By Irene Mona Klotz, Discovery News
Oct. 21, 2005— The Mars rover Spirit capped a year-long quest to reach the top of a group of hills and has begun climbing down to explore a new region of its Gusev Crater landing site.
The descent could take a month or longer, depending on how many targets Spirit stops to study and how well it continues to operate.
"We're on new ground now, and we're going to be seeing some new sights," said rover principal investigator Steven Squyres with Cornell University. "Spirit has really been on a roll lately."
Getting to the last target on Husband Hill tested the team's mettle. Perched on a steep slope and with loose soil beneath the rover's wheels, rover operators were not sure what would happen when Spirit's sensor-laden arm was extended to study a rock named Hillary.
The team decided to wiggle the rover's wheels to test how stable it was. To scientists' dismay, the rover moved.
"A little motion isn't unexpected when you wiggle wheels on a slope this steep, of course, but it wasn't exactly a confidence-builder," Squyres wrote in his project's Web log.
The team was concerned that if the rover slipped with its arm extended, it might bump the delicate instruments into the rock. After a day of brain-storming, rover operators decided to partially extend the arm and see if Spirit held its ground. The rover was steady and the team collected data for several days.
Scientists were able to determine that the rocks at the top of the hill are nearly indistinguishable from rocks hundreds of yards away, though they are angled quite differently.
"All in all, it was a crucial piece of the puzzle in trying to work out the geology of Husband Hill," Squyres wrote.
Spirit will make its way along a ridge and head toward an area known as "Home Plate," located about a half-mile from the summit of Husband Hill.
"We don't know what this is, but it looks geographically interesting," said science team member Larry Crumpler, with the Museum of Natural History in Albuquerque, N.M. "We think it will help us to understand what the hills are all about."
Ultimate, the team wants to reach a basin-like area south of the Columbia Hills.
Spirit and its identical twin rover Opportunity have been exploring Mars for nearly two years in an effort to determine if and for how long the planet had liquid water, which scientists believe is a key requirement for life.
Opportunity, which is exploring on the other side of the planet in an area known as Meridiani Planum, has recovered from a series of glitches and is headed around Erebus Crater, a shallow depression stretching about 300 meters, or 984 feet, in diameter.
The rover's destination is an area known as Mogollon Rim.
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