Recent discoveries have shed new light on the history of Mars, revealing evidence of ancient underground water that suggests the planet may have been habitable for longer than previously believed.

Billions of years ago, Mars was not the arid, desolate planet we know today. Evidence suggests that rainfall once flowed across its surface, carving valleys, filling craters, and forming river ...

Why it matters: The dream of colonizing Mars has captivated everyone from billionaires and planetary scientists to Star Trek fans. However, a significant practical challenge to this vision has been ...

Water is ubiquitous on Earth—about 70% of Earth's surface is covered by the stuff. Water is in the air, on the surface and inside rocks. Geologic evidence suggests water has been stable on Earth since ...