That raises the question...
...when a new comet is produced, what event could it be
- that would change the material's trajectory so it would visit the inner solar system, but
- would not smear its structurally nonsubstantive (pretty sure I made up a word, here) mass all over the place?
Or maybe when the trajectory is modified, the mass exists as a cloud that gradually pulls itself together on its long first trip towards the sun?