Gas release from comets

The quantities of such volatiles as CO, CO2, and CH4 trapped in cometary water ice are of great importance in the determination of solar nebula temperature and composition in the regions of their formation. Experiments with water ice are presently noted to retain trapped gases beyond the temperature of amorphous ice's transformation to cubic ice; the retention of gases which emerge during the transformation of the cubic form to hexagonal (as well as during evaporation) occurs to a degree that is linearly dependent on the thickness of the ice layer.