Earth's geocorona from the Moon during Apollo 16, 1972. Far-ultraviolet filtered image of the geocorona, a halo of low-density hydrogen around Earth. The filter used blocked the glow caused by atomic hydrogen, but transmitted the glow caused by atomic oxygen and molecular nitrogen. Airglow emission bands are visible on the night side of Earth. This UV camera was operated on 21 April 1972 by US astronaut John W. Young on the Apollo 16 lunar landing mission.