Spacewalkers began assembling the new robot on the first of five space walks planned for the shuttle Endeavour's current mission.

The U.S. government is tightening the amount of ozone—a main ingredient of smog—allowed in the air, but not by as much as scientists recommended.

The powerful repellant temporarily jams an insect's sense of smell so that people don't register as food, according to a new study.

A drug-dispensing robot is filling many of the prescriptions at Bumrungrad International Hospital in Bangkok, Thailand. Makers say the machine is more reliable than humans.

Humans crossed the Bering land bridge 22,000 years ago but couldn't escape ice there for thousands of years, according to a combined genetic and archaeological analysis.

A study suggests 95 percent of Native Americans can trace some DNA back 20,000 years to just six women.

A pair of meteorites discovered in Antarctica is baffling scientists, who are struggling to determine the the space rocks' origins.

The northern lights—aurora borealis—delight sky watchers during the dark days and nights of fall, winter, and spring in the Arctic islands of Norway.

The international Cassini spacecraft is plunging through the geyser plumes of Saturn's moon Enceladus today to learn how they formed.

A human-size boulder that crashed into southern Peru in September 2007 was one large fragment, challenging long-held views that meteors crumble into smaller pieces before hitting Earth, experts say.

NASA's first nighttime launch since 2006 sent Endeavour on a 16-day space station mission. Astronauts will install a Canadian robot and a Japanese storage unit.

Rising seas, thawing Arctic ice, and more heat waves, rainstorms, and hurricanes will all affect U.S. travel by train, boat, and plane, a new report says.

The seven tiny feathers could fill a key gap in the puzzle of how dinosaurs gave rise to flying birds, a new study says.

With NASA's first nighttime shuttle launch since 2006, Endeavour begins its mission to assemble a Canadian robot and install a Japanese-built "float-in" closet at the International Space Station.

See the evidence for a new theory of tiny humans—and the stunning South Pacific setting where it was found.