  We present experimental results on crystal--amorphous transition of
forsterite (Mg2SiO4) silicate under ion irradiation. The aim of this work is to
study the structural evolution of one of the most abundant crystalline
silicates observed in space driven by ion irradiation. To this aim, forsterite
films have been sythesised in laboratory and irradiated with low energy (30--60
keV) ion beams. Structural changes during irradiation with H+, He+, C+, and
Ar++ have been observed and monitored by infrared spectroscopy. The fraction of
crystalline forsterite converted into amorphous is a function of the energy
deposited by nuclear collision by ions in the target.
  Laboratory results indicate that ion irradiation is a mechanism potentially
active in space for the amorphisation of silicates. Physical properties
obtained in this work can be used to model the evolution of silicate grains
during their life cycle from evolved stars, through different interstellar
environments and up to be incorporated in Solar System objects.
