The atmosphere of Mars has a distinctive green glow, just like Earth. It was thanks to the European Space Agency’s Tracking Gas Orbiter (TGO) that has detected an emerald glow in the thin atmosphere of Mars.
“One of the brightest emissions observed on Earth comes from the nighttime glow. More specifically, from oxygen atoms emitting a particular wavelength of light that has never been seen around another planet,” commented Jean-Claude Gérard of the University of Liège in Belgium and leader of the work. “However, this emission is expected to exist on Mars for about 40 years, and thanks to TGO, we have found it.”
Thus, this green emission is characteristic of oxygen. On Earth, we see them as auroras, which are generated by charged particles from the Sun that collide with molecules high in the atmosphere. But the night glow is different. It is caused by the interaction of sunlight with atoms and molecules in the air, which generates a subtle but continuous light. This broadcast is difficult to see, even here on Earth.
“Night glow occurs when broken molecules recombine, while daytime glow arises when sunlight directly excites atoms and molecules such as nitrogen and oxygen, ” wrote experts from the European Space Agency (ESA).
Previously, no green glow had been captured on Mars, but this time they found that green oxygen glowed at all heights, although it was strongest at about 80 km and varied with the distance from the red planet to the sun. The oxygen atoms glowed in both visible and ultraviolet light, with a visible emission about 16.5 times stronger than UV radiation.
“The observations on Mars are in agreement with previous theoretical models, but not with the actual brightness that we have seen around Earth, where the visible emission is much fainter,” Gérard said. “This suggests that we have more to learn about how oxygen atoms behave, which is very important to our understanding of atomic and quantum physics.”
