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Science notes / Astronomy, anatomy

Comet has fragile surface

Close-up images of comet Tempel 1 taken by the Stardust spacecraft on Valentine's Day suggest that the comet's surface is much more fragile than astronomers had anticipated, with major changes occurring during its five-year orbit of the sun, researchers said.

The pictures also showed an unexpected layering of the comet's interior, a feature that researchers had not detected in 2005, when an earlier mission shot an 820-pound impactor into the comet's side. Scientists hope to learn more about the comet's surface, interior, the dust particles it gives off and about how a comet changes over time, said mission principal investigator Joe Veverka.

The rendezvous brought Stardust within 110 miles of Tempel 1. Stardust snapped photos every six seconds. From the images, scientists can see that the man-made crater is about 150 meters across and "subdued," meaning it is not as well-defined as had been expected, said co-investigator Peter Schultz, a planetary geologist at Brown University in Providence, R.I. The images also showed that material that had been thrown up by Deep Impact had fallen down again to form a small mound in the center of the crater.

Veverka noted that a depression in the comet's surface had visibly changed shape and lost a substantial amount of material. The researchers were able to get a glimpse at other sides of the comet they had not seen before, finding areas where the rocky surface appeared thickly layered and other regions that looked heavily pocked and pitted.

-- Los Angeles Times

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Upright walking evolved early

Our celebrated ancestor Lucy was no waddling, hunched-over ape-woman who felt more at home in the trees. New research from the University of Missouri in Columbia offers the most conclusive evidence yet that Lucy and her tribe spent their lives on solid ground and walked much as modern humans do -- more than 3 million years ago.

Lucy, just 3 1/2 feet tall, would have been more capable of strutting her stuff on a dance floor than of swinging from branch to branch.

In research published in the journal Science, MU anatomy professor Carol Ward and two colleagues used a newly discovered foot bone from a dig in Ethiopia to determine that members of Lucy's species, Australopithecus afarensis, had arched feet like ours. Arches made it possible to comfortably stand and walk. But arches also took away the flexibility that lets apes grasp with their feet as they scramble up trees.

"This tells us she's given up the ability to be good in trees to be good on the ground. There was no more compromise. We can walk well over distances, and that started with Australopithecus. It turned out to be a good plan for us," Ward said.

-- Kansas City Star

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