A material which is composed primarily of chemical elements and compounds with relatively low boiling points, equilibrium condensation temperatures below 1300 Kelvin, and which are part of the crust or atmosphere of a moon or planet.

Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide. In astrogeology, these compounds, in their solid state, often comprise large proportions of the crusts of moons and dwarf planets.