Preliminary study for future ESR dating of solid SO2

Paramagnetic properties of irradiated solid SO2 have been studied for future ESR dating of icy materials on Io, the satellite of Jupiter. Radical species in solid SO2 formed by irradiation with γ-rays were measured with ESR at various temperatures to obtain the isothermal decay data, which gave their lifetimes at the ambient temperature on Io by the extrapolation in the Arrhenius plot. ESR parameters and speculative models for observed signals are presented.