Properties of ices and grains - An experimental study

Proton irradiation of a variety of ice mixtures was carried out to study the effect of galactic cosmic ray irradiation of comets in the Oort Cloud. Three significant effects were noted: (1) production of new molecules; (2) production of a more energetic ice at low temperatures; (3) production of a non-volatile, complex organic residue. These phenomena suggest various effects on new comets approaching the sun including enhanced activity. Experiments on the condensation of silicate grains provide information on the condensation mechanism and properties of grains. Controlled annealing of the amorphous condensates shows how crystallization occurs. Infrared spectra of different stages of crystallization contain features that may identify composition, structure and history of refractory material.