Plasma and UV photon bombardment of an icy object in the outer solar system can lead to ejection of atoms and molecules from the surface which can, in turn, produce an extended neutral atmosphere. We present new laboratory studies of the sputtering of water ice by keV ions (H+ through Ne+) made using a sensitive microbalance technique that allows measurements at very low ion fluences. These results for the sputtering yield of ice by keV O+ ions, the dominant sputtering agents in the Saturnian magnetosphere, are much larger than those used previously to model the neutral cloud associated with the icy satellites. The data presented are used to recalculate previously published sputtering rates for the icy satellites of Jupiter and Saturn, and for the E-ring grains at Saturn. The new results can account, in part, for the discrepancy between the predicted and observed OH cloud near Tethys in Saturn's inner magnetosphere. We compare the yields induced by the incident ions to the recently measured UV photosputtering yield, and discuss possible synergism between UV photon and plasma ion induced erosion. ¿ American Geophysical Union 1995