Mars may be the Red Planet, but its atmosphere glows green.
Using the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter (TGO), scientists have observed Mars’ atmosphere glowing green for the primary time ever — within the visible light spectrum, that’s.
The effect is known as airglow (or dayglow or nightglow, depending on the hour), and it occurs on Earth, too. While it shares some similarities with the northern lights (or aurora) here on our planet, it’s a unique phenomenon with different causes. Nightglow, specifically, “occurs when two oxygen atoms mix to form an oxygen molecule,” in keeping with ESA. On Mars, this happens at an altitude of roughly 31 miles (50 km). By comparison, auroras occur when charged particles from the sun collide with Earth’s magnetic field.
Scientists have suspected Mars to have airglow for some 40 years, but the primary remark only occurred a decade ago by ESA’s Mars Express orbiter, which detected the phenomenon within the infrared spectrum. Then, in 2020, scientists observed the phenomenon in visible light using TGO, but in Martian daylight moderately than at night. Now, we have seen the phenomenon at night via TGO.
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“These latest observations are unexpected and interesting for future journeys to the Red Planet,” ULiège planetologist Jean-Claude Gérard,” said in an ESA statement. “The intensity of the night glow within the polar regions is such that easy and comparatively inexpensive instruments in Martian orbit could map and monitor atmospheric flows. A future ESA mission could carry a camera for global imaging. As well as, the emission is sufficiently intense to be observable in the course of the polar night by future astronauts in orbit or from the Martian ground’.
Studying Mars’ nightglow, which is able to proceed as a part of the TGO mission, will even give scientists insight into processes that occur within the Martian atmosphere. “Distant sensing of those emissions is a wonderful tool for probing the composition and dynamics of Mars’ upper atmosphere between 40 and 80 km [25 to 50 miles],” said Benoit Hubert, a researcher on the Laboratory for Planetary and Atmospheric Physics (LPAP) on the University of Liège. “This region is inaccessible to direct methods of measuring composition using satellites.”
Studying Mars’ atmosphere also can help with the design of future spacecraft destined for the Red Planet. A greater understanding of its density may also help mission planners construct satellites that may withstand the drag the Martian atmosphere creates, for instance, or design parachutes that may lower payloads right down to the Red Planet surface.
The team’s research was published within the journal Nature Astronomy on November 9.