Laboratory measurements simulating the impact of certain solar wind ions on CO have been made. Preliminary analysis of the X rays in the 50–300eV energy range produced by these collisions suggests that a dominant role is played by electron capture and subsequent relaxation of the electron to the n=2 levels of solar wind ions such as Ne and S. In particular our data show that X rays from Ne play a role that is at least as significant as that of the more dominant solar wind ion O 6+ in this X-ray energy range. It may be assumed that Mg and Si may also play an important role; however, these ions were not included in the present experiment.