According to Quantum FFF Theory, comet nuclei are plasma producing new physics black holes with a Fermion repelling horizon around the nucleus.
Crashed comets even seem often to split before crashing into stars, (forming starspots) planets or moons leaving extra peculiar pensil shaped gravity patterns behind. (see Orientale basin).
see also:
https://www.flickr.com/photos/93308747@N05/albums/72157651837150515
