Extinct comet

In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface layer.

When volatile materials such as nitrogen, water, carbon dioxide, ammonia, hydrogen and methane in the comet nucleus have evaporated away, all that remains is an inert rock or rubble pile.

[5] Minor planets of the group of damocloids have been studied as possible extinct cometary candidates due to the similarity of their orbital parameters with those of Halley-type comets.

For example, 14827 Hypnos may be the nucleus of an extinct comet that is covered by a crust several centimeters thick that prevents any remaining volatiles from outgassing.

[7] When discovered, asteroids were seen as a class of objects distinct from comets, and there was no unified term for the two until "small Solar System body" was coined by the IAU in 2006.