The morphology of interstellar water ice

We have studied, by infrared absorption spectroscopy, the effects of ion irradiation (with 200 keV protons) on the morphology/porosity of thin amorphous water ice (H2O) samples at 15 K. We have found that the intensity of the OH dangling bond feature decreases after ion irradiation and that the amount of carbon monoxide (CO) absorbed in water ice decreases as the fluence of impinging ions increases. These results indicate that the porosity of amorphous water ice decreases after ion irradiation. Here we present the experimental results and suggest that because of cosmic ray bombardment water ice in interstellar grain mantles is compact in structure