A mysterious glow has been detected emanating from the night side of Mars by a satellite from the European Space Agency (ESA). The glow was measured in the visible spectrum with the NOMAD-UVIS instrument on board the ESA’s Trace Gas Orbiter (TGO) satellite. Researchers believe that the glow is a result of the interaction between oxygen and the planet’s upper atmosphere. The same research team had previously observed a similar glow from Mars during the daytime, as well as a glow from Venus. The presence of this glow during the night time was unexpected and originated from the recombination of oxygen atoms in the summer atmosphere carried by winds towards the high winter latitudes.

The researchers reoriented the UVIS-NOMAD instrument on the TGO satellite to scan the atmosphere on its edge, and quickly detected the light emissions concentrated over the polar regions of Mars. The oxygen atoms converge in the downward branch of their trajectory from the opposite hemisphere. Furthermore, the researchers also discovered a glow in the ultraviolet range, which they believe is caused by the nitric oxide (NO) molecule.

The detection of this mysterious glow provides important insights into the dynamics of Mars’ upper atmosphere and its seasonal variations. The study will be continued during the TGO mission, with hopes of gathering more information about the Martian year. The observations of the glow may also aid in guiding future missions to Mars, as the intensity of the night glow in the polar regions suggests that inexpensive instruments in Martian orbit could map and monitor atmospheric flows. Future astronauts in orbit or on the Martian ground might even be able to observe the glow during the polar night.