Two rovers on Mars into serious science

WASHINGTON — WASHINGTON - The two rovers on Mars are getting down to some serious science, mission officials said yesterday, with Opportunity providing a close look at some intriguing granules of material that may have formed in the presence of water.

Steve Squyres, the lead scientist for the rover mission, said the weekend had proved "probably the biggest two or three days of science since we landed."


The Opportunity rover, which landed Jan. 25, has been exploring a bedrock outcropping within a small crater on the flat expanse of Meridiani Planum.

Spirit on the move


Spirit, which landed Jan. 3 and had been disabled by software-related problems for about two weeks, is on the move again on the other side of Mars. After identifying a rock nicknamed Adirondack as clearly of volcanic origin, Spirit is to examine a light-colored rock nearby, Squyres said. It will then head for a small crater about 270 yards away.

Squyres said the Meridiani site is "where the really crazy looking stuff is." At both Meridiani and Spirit's landing site, the Gusev Crater, scientists are looking for evidence that Mars once might have been a wetter place and perhaps more hospitable to life.

The layered bedrock being explored by Opportunity has been of particular interest. Scientists have suggested it could be the result of repeated episodes of falling volcanic ash or, more intriguingly, the buildup of waterborne sediments.

Microscopic images of the bedrock show it has fine layers imbedded with tiny, gray granules of material "like blueberries in a muffin," Squyres said.

During a news briefing at the Jet Propulsion Laboratory in Pasadena, Calif., he said the matrix of tan layers might be an accumulation of volcanic ash or fine-grained Martian dust that has been compacted into sedimentary rock. If it is compacted dust grains, he said later, it is not clear whether the grains were brought to the site by the action of water, wind or a combination of both. "We can't say just yet," Squyres said.

Possibly 'concretions'

As for the beadlike granules within the layers, Squyres said, they might be "concretions," structures that can form when water diffuses through a material, causing minerals to precipitate out.

But there are other possibilities. The beads might have formed from molten rock sprayed about by volcanic eruptions or meteor impacts. Ash from volcanoes also can clump into spheres, Squyres said, though they would tend to be made of the same material as the matrix in which they are found


The color difference between the beads and the rest of bedrock makes the ash-sphere scenario less likely, he said.

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