Spirit finds evidence of Mars' violent past

Explosions and falling rock once peppered the Martian hills that NASA’s Mars rover Spirit currently calls home, astronomers said Tuesday.

Spirit, currently scaling Husband Hill above its Gusev Crater landing site, has found evidence of an explosive period in the region’s history, in which volcanoes or a massive impact showered the land with debris and possibly unearthed magma. Whether they were volcanic or impact explosions, however, is not yet known.

“Earlier in its history, this part of Gusev Crater was a violent place,” said Steven Squyres, lead scientist from Cornell University for the Mars Exploration Rover (MER) mission. “There were explosions going and there was stuff raining from the sky, and some of it was altered to a significant degree by a fairly modest size of water.”

Squyres and his fellow rover team members announced the find, which is based on a trio of rock outcrops observed by Spirit’s cameras, during a Tuesday press conference at an American Geophysical Union meeting in New Orleans, Louisiana.

NASA / JPL / Cornell / USGS This mosaic of 24 frames from Spirit's microscopic imager shows the texture of a target called "Keystone" on the "Methuselah" outcrop of layered rock on "Husband Hill" inside Mars' Gusev Crater. The target area shows fine layers that may have been deposited by wind or water.

“Really, for the first time since the start of the Spirit mission, we’ve got the kind of geology we can sink our teeth into,” Squyres said. “The last six weeks, I’d say, have probably been the most productive of the whole Spirit mission.”

Spirit’s sister rover Opportunity has also made progress, though not altogether scientific, at its Meridiani Planum. The rover is slowly but surely inching its way out of a deep sand dune, though mission managers don’t expect to free the robot for another few weeks.

The secret’s in the rocks
It took the Spirit rover months to clamber up Husband Hill’s steep, slippery side, during which time the robot found little to suggest the region differed from the volcanic rock remains scattered across the rest of Gusev Crater.

Slide show   Greatest hits from Mars rovers A year’s worth of highlights from NASA’s Spirit and Opportunity robots

But now halfway up Husband, after studying three rock outcrops, researchers are telling a different story.

“All of a sudden, we have geologic structure ... everything changed,” Squyres said. “It was nothing more than you had to look at it from a different angle.”

Analysis by Spirit of rock outcrops known as “Larry’s Lookout,” “Methuselah” and “Jibsheet” contained signs of the Gusev’s tumultuous past, researchers said.

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