Illustration of the European Space Agencys (ESA) ExoMars Trace Gas Orbiter (TGO) detecting the green glow of oxygen in the Martian atmosphere. This emission, observed on the dayside of Mars, is similar to the night glow seen around Earths atmosphere from space. Scientists were able to spot this emission using a special observing mode of the TGO, using the NOMAD (Nadir and Occultation for Mars Discovery) instrument and the ultraviolet and visible spectrometer (UVIS). The NOMAD-UVIS detected green oxygen emission at altitudes ranging from 20 to 400 kilometres from the Martian surface. Studying the glow of planetary atmospheres can provide valuable information about the composition and dynamics of an atmosphere.