happened to collide with the Earth. The best-known episode is that in which the dinosaurs died 65 million years ago, but there have been many other catastrophic impacts both before then, and since.

How did life begin on Earth? While scientists have theories, they don't yet fully understand the precise chemical steps that ...

The Giant Impact Hypothesis has long fascinated scientists as the leading explanation for the Moon's formation. Around 4.5 billion years ago, the Earth and a Mars-sized protoplanet called Theia ...

On August 23, 1966, NASA’s Lunar Orbiter 1 captured the very first photograph of Earth from the vicinity of the Moon, showing our planet as a delicate crescent rising above the lunar horizon. While ...

Since the beginning of Earth's history, tiny particles of rock and metal from space have been hitting our planet. On clear nights, we can even see their traces as shooting stars. Trapped in layers of ...

Close your eyes. Think of the Earth. You probably instantly see a blue marble with large patches of lush and green land and wispy clouds swirling around the globe. You know exactly what the Earth ...

Continental clues: Modern continental rocks carry chemical signatures from the very start of our planet’s history, challenging current theories about plate tectonics. Researchers have made a new ...

The discovery that helium and iron can mix at the temperatures and pressures found at the center of Earth could settle a long-standing debate over how our planet formed. When you purchase through ...

CU Boulder professors explain Earth Day’s history, impact, what it’s become and if it’s still relevant If you were at the University of Colorado Boulder in April 1970, you were likely aware―very aware ...

On Sept. 22, the autumnal equinox, which signals the start of fall in the Northern Hemisphere, finally brings an end to our long, hot summer on Monday at 2:19 p.m. EDT. This happens at a precise ...