Fossilized worm burrows show that life had moved beyond the oceans by 530 million years ago. (p. 9)

Any 10-year-old knows how the dinosaurs met their end: A huge meteorite slammed into Mexico’s Yucatán Peninsula 65 million years ago, blasting the planet beyond anything imagined by Bruce Willis in Armageddon. But neither kids nor Hollywood have spent much time thinking about how dinosaurs appeared in the first place. “We know a heck of a lot more about the extinction of dinosaurs than their origins,” says Randall Irmis, a paleontologist at the Utah Museum of Natural History and the University of Utah in Salt Lake City. Lately, though, new discoveries have begun to flesh out the scrip... (p. 22)

KENNEDY SPACE CENTER, Fla. — NASA saved one of its best for nearly its last. Friday’s scheduled launch of the space shuttle Endeavour — its last flight, and the second-to-last planned for any shuttle — will be carrying an ambitious and potentially pioneering particle physics experiment. The $2-billion, 7.5-ton Alpha Magnetic Spectrometer, or AMS, is destined to nestle along the backbone of the International Space Station, there to study charged particles streaming through space. Designed to hunt for exotic stuff such as dark matter and antimatter, the AMS may also make fundamental dis...

A "drip" deep within the Earth may have raised the Colorado plateau to create the spectacular landscape of the U.S. Southwest. (p. 12)

Last year’s eruption in Iceland spit out supersharp and potentially harmful particles, nanoscale images show.

Hole over Antarctica changes weather patterns all the way to the equator, simulations suggest. (p. 15)

Japan tremor may be part of a second grouping of great quakes since 1900, some scientists say. (p. 5)

Bacterial colonies form cones similar to fossilized examples of Earth’s early life. (p. 10)

In ancient times, listing the ingredients of the universe was simple: earth, air, fire and water. Today, scientists know that naming all of that, plus everything else familiar in everyday life, leaves out 95 percent of the cosmos’s contents. From the atoms that make up an astronomer, to the glass and steel of a telescope, to the hot plasma of the stars above — all ordinary stuff accounts for less than 5 percent of the mass and energy in the universe. “All the visible world that we see around us is just the tip of the iceberg,” says Joshua Frieman, an astrophysicist at the Univers... (p. 24)

Flowing glaciers help scientists study climate change.