Science Digest

Meteorite Scavengers

NASA scientist Steve Chesley got a call at home last October with bracing news: A telescope in Arizona had spotted an SUV-size asteroid that appeared to be on a collision course with Earth. He raced to work, ran a computer calculation and saw something he had never seen before: a 100 percent chance of direct impact.

He quickly checked to make sure the asteroid was the size advertised. It was. No reason to panic.

Hours later, the asteroid hit the atmosphere over northern Sudan's Nubian Desert and exploded 23 miles up with the force of a thousand tons of TNT. Witnesses saw the fireball and took pictures of the vapor trails in the sky.

That might have been the end of the story, but Peter Jenniskens, an astronomer at the SETI Institute in California, had an idea: Why not search the desert for meteorites -- the fragments from the space rock?

In December, Jenniskens, professor Muawia Shaddad of the University of Khartoum and dozens of Shaddad's students scoured the desert for traces of the asteroid. Finally, they found one -- and then 46 more, the largest the size of an egg.

It was the first time scientists had observed an asteroid telescopically and then recovered its fragments. By comparing the data gleaned from observing the asteroid in space with analysis of the recovered meteorites, researchers can calibrate their telescopic observations of other asteroids. The findings were published last week in the journal Nature.

"It's the first step toward a Rosetta stone for understanding asteroids," Michael Zolensky of NASA's Johnson Space Center and one of the study's authors, told reporters in a conference call.

-- Joel Achenbach

How Video Games Help

Next time you worry about video games ruining your kids' eyesight, you might want to consider some research that suggests the opposite. Video games apparently can improve a key component of eyesight: discerning slight differences in contrast.

Daphne Bavelier of the University of Rochester and her colleagues studied 22 students before and after they played video games. Half of the students played the action video games Unreal Tournament 2004 and Call of Duty 2, while the others played The Sims 2, which is also richly visual but does not have the same level of visual-motor coordination of the other games.