Effects of charged particles on the surfaces of the satellites of Uranus

Measurements of the ion and electron fluxes in the Uranian magnetosphere made by the low‐energy charged particle (LECP) instrument on the Voyager 2 spacecraft are used to discuss possible particle‐induced modifications of the moons and rings of Uranus. The energy spectra of the orbit‐integrated particle dosages expected on the major moons are derived from the LECP measurements of particle intensities and pitch angle distributions. Laboratory‐derived results on charged‐particle‐induced chemical and physical modifications of H 2 O, CH 4 , CO, and CO 2 ions are used. The erosion rates of water ice and the darkening of organic ices on the surfaces of the moons are estimated from the orbit‐integrated fluxes. Significant darkening of fresh organic ices to depths of the order of a micron is expected to occur for times as short as a few thousand years. Darkening at deeper depths will occur at increasingly longer times. The implications of these results for the interpretation of remote sensing data from such objects are discussed.