After spending 160 days traversing a plain and climbing a steep hill, the Mars explorer Spirit is finding the first strong indications of significant quantities of water at Meridiani Planum.
Spirit’s twin, Opportunity, has found powerful evidence of water halfway around Mars in Gusev Crater, but until now Spirit has had less success. Both NASA craft have been exploring the geology of the planet since landing in January.
After performing a complicated switchback climb to reach an altitude of about 30 feet in the Columbia Hills, Spirit is parked at an outcrop of bedrock called Longhorn that shows strong signs of weathering by water.
The key feature of Longhorn, said principal investigator Steven Squyres of Cornell University, is the presence of two different kinds of rocks, “some gray, others light-toned, crumbly and cruddy.”
Squyres suspects but has not yet proved that the rocks represent a “before and after” pair. The gray rocks appear to be relatively pristine, while the lighter ones have undergone some kind of alteration. There are several possibilities for how that alteration could have occurred, but the most likely is the action of water, he said.
“This is different from the rocks out on the plain, where we saw coatings and veins apparently due to the effects of a small amount of water,” Squyres said. “Here we have a more thorough, deeper alteration, suggesting much more water.”
So far, however, they have determined the composition of only the “after” rocks, so they can’t make a definitive statement. The team used the rover’s rock abrasion tool to drill a hole into the rock’s interior.
“This is one of the softest rocks we have encountered” on Mars, said geologist Doug Ming of the Johnson Space Center. It also has very high concentrations of sulfur, chlorine and bromine, which might have been deposited in the rock by water.
Opportunity, meanwhile, has descended about 30 feet into Endurance Crater, a small crater in Gusev, and is encountering unusual rocks as well. Gusev is littered with large numbers of small, round rocks that the team has called blueberries.
But now the craft has encountered some similar stones that are also round, but are lighter and redder. “We have no idea what they are,” said Zoe Learner, a graduate student at Cornell who is part of the science team. The stones are very coarse and rough, unlike the smoother blueberries, and are more irregular in shape. Some even appear to have blueberries inside them.
Spirit and Opportunity are showing the stresses of old age, but are continuing to perform well, mission controller Chris Salvo said. Both are well beyond their designed three-month lifetimes, but they “are not showing any signs that they are going to stop.”
Associated Press
A view from one of the Mars rovers shows the planet’s surface in a photo released by NASA on Wednesday.
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