Ongoing drought - and increasing temperatures - have reduced water flow in the Colorado River, with more dramatic reductions expected. This ongoing, unprecedented event threatens water supplies in cities in the U.S. West and some of the most productive agricultural lands anywhere in the world.

Saturn's moon Iapetus is a world of contrast, with light and dark regions fitting together like cosmic puzzle pieces.

A new analysis suggests the likely answer is yes — though not an identical twin. And so did every other sunlike star.

Researchers have uncovered 300,000 year-old fossil bones of Homo sapiens in Morocco, the oldest reliably-dated fossil evidence of our species yet.

Watch this video, showing Earth spinning under the sky of the southern Everglades in Florida.

Words often fail when trying to explain the kaleidoscope of sights, sounds, feelings and emotions that consume us during this other-worldly event.

Most galaxies are randomly oriented in space, but the biggest ones often point toward their neighbors. A new study traces these alignments back into the early universe.

The ice sheets are melting from both above and below, say scientists.

Cottonwood trees in the American West are a nuisance to some and a treasure to others. They yield shade, beautiful foliage and, in June, a kind of warm, fluffy "snow."

Astronomers used the Hubble Space Telescope to follow the 2 brown dwarfs in the Luhman 16AB system, as they move both across the sky and around each other.