On Earth, this happens in the form of an aura at the poles of the planet, but this is the first time that such a glow has been seen around another planet.
Earth’s polar green glow occurs when electrons from space collide with our upper atmosphere, but the atmosphere of Earth and Mars glows both day and night thanks to sunlight. At night, a glow is created when molecules in the atmosphere that were decomposing reunite. During the day, glow occurs when sunlight mixes atmospheric molecules and atoms, such as nitrogen and oxygen.
Astronauts on the International Space Station have the best view of the Earth’s bright green night glow because their perspective is “edge farther,” meaning they can see at an angle that makes the glow more visible.
This is because our planet has a bright surface, which can overcome that faint glow. It’s the same with other planets, which is why this discovery of the green glow around Mars is so exciting.
“One of the brightest emissions seen on Earth comes from the night glow. More precisely, from oxygen atoms that emit a certain wavelength of light that has never been seen around another planet,” said Jean-Claude Gérard, lead author of the study and astronomer and professor at Université de Liège in Belgium, in a statement.
“However, it is predicted that this show will exist on Mars for about 40 years – and, thanks [Trace Gas Orbiter], we found him. “
The ExoMars Trace Gas Orbiter established an orbit around Mars in October 2016. Some orbiter instruments, collectively referred to as NOMAD (Nadir and Occultation for the Discovery of Mars), are aimed at the surface of Mars during orbit. These instruments include an ultraviolet and a visible spectrometer, or UVIS.
Hoping to find a green glow, they focused on instruments to see Mars on the “edge” and scan at different altitudes twice per orbit between April 24 and December 1, 2019. Altitudes ranged from 20 to 400 kilometers (12.4 to 249 miles) from the surface of the planet.
An excellent green glow was found in all the data collected during that time – and an impressive feat for orbits, given that Mars’ atmosphere during the day glows much brighter than at night and makes the green glow harder to recognize, the researchers said.
“The emission was strongest at an altitude of about 80 kilometers and varied depending on the variable distance between Mars and the Sun, ”Ann Carine Vandaele, co-author and principal investigator of NOMAD at the Institut Royal d’Aéronomie Spatiale de Belgique in Belgium, said in a statement.
What’s in the green glow?
Comparing the two planets, the researchers found that Mars’ green glow is different from that on Earth.
“We modeled this emission and found that it is mainly produced as carbon dioxide, or CO2, [and] it breaks down into its constituent parts: carbon monoxide and oxygen, “Gérard said.” We have seen the resulting oxygen atoms glow in both visible and ultraviolet light. “
While this agrees with the theoretical models that suggested that Mars would have that glow, it is much stronger than the visible emission created by Earth.
“This suggests that we need to learn more about the behavior of oxygen atoms, which is extremely important for our understanding of atomic and quantum physics,” Gérard said.
Observing the glowing planetary atmosphere can reveal their composition and the energy they receive from both sunlight and the sun’s solar wind or a stream of charged particles moving through the solar system.
This is also critical to understanding the aura. By studying Mars’ green glow, researchers can understand the structure of this layer in the planet’s atmosphere, better understand its altitude range, and even observe any changes in the reaction to the sun.