Hi Michael -

Cometissimals are not fomed from loose gas, but from LOOSE MOLECULES in a near vacuum, including molecules of the heavier elements.

We have samples here on Earth of both asteroids and comets. These samples are known as meteorites, and the samples spectrally match with their parent bodies, the comets and asteroids. While it appears that some comets do become asteroids, specifically carbonaceous chondrites [S? G? class], most asteroids had a different origin. We know this from studying how their meteorites formed.

"icey dirtballs" works best as a description of comets. Think back to your childhood of a sooty snowball with a rock at its center... they weren't very nice to you then, now were they... but children can be so cruel... people as well..

Appearances can be decieving, and different quacks will often try to decieve you with appearances. While freshly exposed comet surfaces outgas, it is a mistake to think that the evaporation of volatiles generally leads to comet fragmentation. Gravitational stresses appear to be a much better mechansm...

As far as densities go, the physical mechanics of both hyper-velocity impacts and low speed collisions are pretty well known... they are used all the time for designing cannon shells and designing car bodies...

Finally, you have to remember that most of these processes take place over billions and billions of years, as Carl Sagan used to say... and why isn't he here, now that we really need him....

I hope I have been able to answer some of your questions, and you will not think me rude if I am not always so responsive... I do get busy at times, and it has been your good fortune that this has not been one of them...

I hope someone else will be able to answer your questions on comas and particles for you