This animal is in a different league from comets - I mean, totally.

Impacts from comets and meteoroids change the surface of the Earth.

They are thought to originate as debris from sun-grazing comets.

Is there any evidence that substantial amounts of material from comets has been delivered to the planets?

Even water from impacting comets remains around the edges of craters.

Some believe the water was here from the start; some think it came later, from comets.

Whether the material comes from comets, gas clouds or other stars remains a matter of speculation.

There is also the threat from comets coming into the inner Solar System.

From comets to quasars, there is always something fascinating to discuss in the Universe.

The thought struck him that water from comets played a role in creating the earth's oceans.