Dark matter. Can a comet be composed of dark matter? If it can, what happens if earth gets hit by a dark matter comet? Is it the same as when a "regular" comet collides?
The things that hit the Earth are asteroids, not comets. So the better question would be, Can an asteroid be composed of dark matter? And if so ...
I think the answer given would be No. For one thing, dark matter can't "hit" regular matter (come into physical contact), because it doesn't interact with regular matter at all, except gravitationally. That still leaves the question whether dark matter could form clumps, like regular matter does, as in asteroids, or planets. And if not, why not? Does dark matter gravitationally attract itself? Do we need another word for this, rather than "matter"?