Because of the interest in atomic emissions observed from the Io plasma torus, we have investigated the spectrum produced by proton impact on SO2 in the wavelength region of 380--800 nm. The proton energy was varied from 50 to 225 keV. The spectrum shows numerous S, O, S+, and O+ lines. A weak series of SO2 bands has also been tentatively identified. In addition, Balmer series lines are seen, which indicates charge-transfer ionization of the SO2 target. Preliminary absolute emission cross sections on the order of 10-18 cm2 have been measured for the most dominant line in the spectrum, an oxygen triplet at 777 nm. ¿ 2001 American Geophysical Union