Comets are instantly recognizable by their tails of gas and dust. Most comets originate in the far, frozen reaches of our Solar System, and only visit the inner Solar System occasionally. But some are in the Main Asteroid Belt, mixed in with the debris left over after the Solar System formed.
Astronomers just found water vapour coming from one of them.
“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early Solar System can be preserved in the asteroid belt.”
Michael Kelley, University of Maryland