Science Notes

Article excerpt

Stardust Insights Come From Earth-Bound Meteors

At first glance, studying dust would seem to promise all the excitement of watching dust collect. Unless, of course, that dust comes from outer space.

Researchers have long analyzed the chemical composition of cosmic dust. The work has yielded important insights into the evolution of stars. But questions remain about the sources of cosmic dust. By some accounts, it comes from stars whose atmospheres are cool enough for material to condense.

To help fill in the picture, researchers at Washington University in St. Louis analyzed dust found embedded in primitive meteorites. By measuring the levels of various isotopes in the grains, they've added two more candidates: red giant stars in the final stages of life, and supernovae - very massive stars that end their lives in a cataclysmic explosion.

Based on their findings in the lab and on current notions of stellar evolution, the team reckons that red giants form the grains as their atmospheres expand and cool. The supernovae generate the dust during the violent mixing of elements that takes place as the shock wave moves through what's left of the star's atmosphere and into space.

Bi-peds' swinging ancestor

Eighteen million years ago there was Proconsul, an early ape that walked on all fours. Three-and-a-half million years ago, there was Australopithecus afarensis, which walked on only two. But what happened in between? How did apes evolve to climb, hang, and swing? Researchers in Spain recently reported finding a nearly complete fossilized skeleton of the ape Dryopithecus laientanus, which dates 9.5 million years ago.

To gain insights into how locomotion evolved, researchers need to study the skeletal elements associated with movement. But these elements are extremely rare.

Hence the completeness of Dryopithecus is seen as a boon. According to the research team that discovered the fossilized ape, the skeleton is clearly adapted to the kinds of motions seen in today's orangutans, a distant relative of Dry's. …