Artist’s impression of ESA’s ExoMars Trace Gas Orbiter detecting the green glow of oxygen in the Martian atmosphere. Credit: ESA
Many photographs taken from low-Earth orbit, especially from the Space Station while on the night side of Earth, show a thin line of green or yellowish light just above the limb of our planet. This is called airglow, and it’s caused by excited oxygen atoms high in the atmosphere releasing energy in the form of both visible and ultraviolet light. Up until recently this has only been seen around Earth. But between April and December of 2019, ESA’s ExoMars Trace Gas Orbiter detected glowing green oxygen in the daytime atmosphere of Mars, making it the first time this phenomenon has been observed around a planet other than our own.“One of the brightest emissions seen on Earth stems from night glow [airglow]. More specifically, from oxygen atoms emitting a particular wavelength of light that has never been seen around another planet,” says Jean-Claude Gérard of the Université de Liège, Belgium, and lead author of the new study published in Nature Astronomy.
[Editor’s note: ultraviolet airglow was first detected at Mars by Mariners 6 and 7 in 1969.)
Airglow, lightning storms, and ...