Sublimation
Sublimation is the process by which a solid state of matter becomes a gas without passing through a liquid state.
In 2259, when attempting to save the Delebs of Persephone III from a cometary impact, the Federation shuttlecraft Galileo was transformed into a heating element that could heat up a portion of the solid surface of comet C/2260-Quentin's nucleus and turned this portion into a gas which could then act as a propulsive force altering the comet's course away from the planet. (SNW: "Children of the Comet")