Re: Comet Tails
Comets loose matter , especially volatile matter, once they get inside the snow border of a solar system (where the heat is enough for ice to vaporize rather than stay in the ice form); that's why comets have tails; comets often have 2 tails, with different directions 'one of dust and one of ice; Hale Bopp shows this.
And comets also break up, split in various parts; another proof they loose matter; they are not permanent and one day, Halley's comet will have expelled all its volatile matter and will resemble all the other asteroids.
Raoul