ESA Science & Technology - Oxygen airglow production mechanism

This animation illustrates the mechanism that leads to production of the oxygen airglow in the upper atmosphere of Venus.

At high altitudes in the atmosphere, on the day-side, the strong flux of ultraviolet radiation coming from the Sun breaks the molecules of carbon dioxide (CO₂) present in large quantities in the atmosphere, liberating oxygen atoms. These atoms are then transported by the so-called sub-solar and anti-solar atmospheric circulation towards the night-side of the planet. Here the atoms migrate from the high atmosphere to a lower layer, called mesosphere, where they recombine into oxygen (O₂).

By doing this, they emit light at specific wavelengths (strongest in the infrared).