A European Space Agency satellite has detected a mysterious glow coming from Mars. Measured in the visible spectrum with the NOMAD-UVIS instrument on board the European Space Agency (ESA) Trace Gas Orbiter (TGO) satellite, the unexpected glow emanates from the night side of Mars and was observed in the planet’s upper atmosphere.
A similar glow was witnessed by the same research team using a satellite orbiting Venus. Like that visible light signal, the researchers believed the mysterious glow coming from Mars resulted from oxygen interacting with the planet’s upper atmosphere. That’s mainly because they also saw a similar mysterious glow coming from Mars, only in the daytime.
“Back in 2020, we were already able to detect the presence of a green emission between 40 and 150 km in altitude, present during the Martian day,” explained Jean-Claude Gérard, a planetologist at the Laboratory for Planetary and Atmospheric Physics (LPAP) at the University of Liège (BE), where the research team was headquartered. “This was due to the dissociation of the CO2 molecule, the main constituent of the atmosphere, by ultraviolet solar radiation”.
However, the researchers soon discovered that this unexpected mysterious glow coming from Mars was originating from the nighttime side. They also figured out it was caused by something else entirely.
“This emission is due to the recombination of oxygen atoms created in the summer atmosphere and carried by the winds towards the high winter latitudes,” explained Lauriane Soret, a researcher at LPAP.
Once at higher altitudes, the atoms recombine with CO2 molecules when they come in contact. This reaction, the researcher explains, produces an oxygen molecule “in an excited state” that relaxes, causing it to emit light “in the visible range.”
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