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A recent discovery indicates that space travelers who land on Mars may see an eerie green glow in the sky, says a study published in Nature on Nov. 9, 2023.

Using data from the Nadir and Occultation for Mars Discovery (NOMAD) spectrometer aboard the ESA’s Trace Gas Orbiter (TGO) spacecraft, which has been orbiting Mars since 2018, the science team observed the Martian atmosphere to glow green (in the visible light spectrum). This phenomenon is known as “airglow” or “nightglow,” occurs when two oxygen atoms combine to form an oxygen molecule, and occurs in the Martian atmosphere at an altitude of 31 miles. Earth also experiences “nightglow,” and is observed to have a bluish hue when viewed from the surface.

Sputnik reported, “in Mars’ case, this emission occurs ‘due to the recombination of oxygen atoms created in the summer atmosphere and transported by winds to high winter latitudes, at altitudes of 40 to 60 km,’ according to Lauriane Soret, one of the authors of the study…”

Live Science reported, “‘These new observations are unexpected and interesting for future journeys to the Red Planet,’ [University of Liège] planetologist Jean-Claude Gérard, said in an ESA statement. ‘The intensity of the night glow in the polar regions is such that simple and relatively inexpensive instruments in Martian orbit could map and monitor atmospheric flows. A future [European Space Agency] mission could carry a camera for global imaging. In addition, the emission is sufficiently intense to be observable during the polar night by future astronauts in orbit or from the Martian ground.'

“Studying Mars’ nightglow, which will continue as part of the TGO mission, will also give scientists insight into processes that occur in the Martian atmosphere. ‘Remote sensing of these emissions is an excellent tool for probing the composition and dynamics of Mars’ upper atmosphere between 40 and 80 km,’ said Benoit Hubert, a researcher at the Laboratory for Planetary and Atmospheric Physics at the University of Liège. ‘This region is inaccessible to direct methods of measuring composition using satellites.’

“Studying Mars’ atmosphere can also help with the design of future spacecraft destined for the Red Planet. A better understanding of its density can help mission planners build satellites that can withstand the drag the Martian atmosphere creates, for example, or design parachutes that can lower payloads down to the Red Planet surface.”

The TGO is a joint project between the European Space Agency and Roscosmos; it was first conceived of in 2008 by NASA, then developed further in 2013 in collaboration with the ESA, and launched in 2016 from the Baikonur Cosmodrome, leased by Russia in Kazakhstan.