One of the most important events for modern astronomy was the series of collisions, during a single week in 1994, of more than a dozen large objects with Jupiter. The collision of these objects, which once formed most of the comet Shoemaker-Levy 9, resulted in formations that showed no signs of water. There was thus no water involved in the collisions
we know that none of the comet' s fragments penetrated to Jupiter' s lower atmosphere and that the comet was composed of rock rather than ice.
Comets tend to be composed largely of ice while asteroids are composed mainly of rock.