Another reason to study comets is that they, along with rocky asteroids, pose a threat of hitting the Earth and causing cataclysmic damage.

A secondary reason to probe comets is that along with rocky asteroids, they pose the threat of cataclysmic damage if they ever strike Earth.

The worst-cast simulation assumed the impact of a rocky asteroid three miles in diameter.

They found high levels of material commonly found in rocky asteroids and rarely found in comets.

Even today, he added, microscopic dust particles from comets and rocky asteroids rain down on Earth at the rate of about 300 tons a year.

Hathor proposed to use the rocky asteroids for target practice.

The Pelagic had emerged from the shelter of the rocky asteroids as soon as the last pod was on its way.

Recent evidence suggests that the objects are icy comets, rather than rocky asteroids.

It has a very bright surface, unusually bright even for a rocky S-type asteroid.

A rocky asteroid was attached to one end, webbed in by a net.