'Dark comets' may be a much bigger threat to Earth than we thought, new study warns

A digital image showing thousands of blue and orange dots surrounding a white circle representing the Earth.

Mysterious, nearly invisible objects known as "dark comets" may pose a bigger threat to Earth than scientists thought, new research suggests. 

These small, rapidly spinning objects wander near Earth, likely after migrating from more distant reaches of the solar system. They might be a source of water and other volatile elements — and also a potent source of danger.