Suggestion: Impacts make permanent dust

[Estwald]

It could be a setting, so you can see how rings form from multiple impacts

[Lord DC]

I second this 

[Gordon Freeman]

Impacts give off permanent dust (I think), it just cools down too much for you to see it.

[Greenleaf]

It could be a setting, so you can see how rings form from multiple impacts

Fragments are initially particles. Some fade and die and some transform into bodies. Those bodies remain. They can eventually collide with other fragment bodies and coalesce into larger objects.
Currently, the fragment count is not terribly high, so most fragments either die early or just fall into some larger body shortly after the collision.

[Lord DC]

I believe he means things like the ring particles.

[Electrodynamix]

No, the fragment particles are the firey globs of fire that come out of planets when you smash things into them...  The ring particles do not have a gravitational pull, like the fragment particles, but the ring particles do not fade out.