X Ray Moon . ... ROSAT Mission , MPE , ESA Explanation: This x-ray image of the Moon was made by the orbiting ROSAT ( R ntgensatellit ) Observatory in 1990. ... Consider the image in three parts: the bright hemisphere of the x-ray moon, the darker half of the moon, and the x-ray sky background. ... Still, the few x-ray photons which seem to come from the moon's dark half are currently thought to be caused by energetic particles in the solar wind bombarding the lunar surface. ...