We present new experimental results on radiolysis of water ice below 140K induced by 150-eV electrons and 100-keV ions, obtained to understand processes occurring in the outer solar system and interstellar space. The experimental methods discussed are low-energy electron-energy-loss spectroscopy (EELS) and Fourier-transform-infrared (FTIR) spectroscopy. The phenomena studied are the formation and trapping of radiation products. in particular H2O2 and radiation-induced amorphization of crystalline ice. (C) 2004 Elsevier Ltd. All rights reserved.