A fossil of an armadillo-like mammal appears to bear cut marks from butchering by humans, suggesting people were living in South America at least 20,000 years ago, even earlier than once thought.

Scientists are analyzing sounds from glaciers to predict exactly how quickly ice is melting and what that could mean for the rise in sea level.

On mountaintop glaciers of Alaska, Washington and Oregon, billions of tiny black worms are tunneling upward to the barren, icy surface. What lures them, and how do they survive the frozen depths?