Water ice on outer solar system surfaces: Basic properties and radiation effects

This paper reviews the properties of vapor-deposited water ice in connection with icy surfaces in the outer solar system. The emphasis is on knowledge gained during the last decade, and on the properties of the amorphous phase, especially those affected by the presence of microporosity. The paper discusses the role played by the properties of different phases of ice and the effect of irradiation on the icy surfaces of satellites in the outer solar system: sputtering, phase transformation, the production and trapping of molecular radiation products, and stress induced cracking. The understanding of how growth and irradiation processes affect the optical properties of ice will lead to extract better information from optical remote sensing than is possible today. It is argued that cracks in ice induced by stresses are the main reason causing low-temperature ices to be strongly scattering.