Experts have discovered a green glow in the Martian atmosphere, the first time that's ever been seen on another planet besides Earth.
The green glow, or light, is a result of oxygen atoms interacting with the sunlight, researchers noted. It had long been theorized to occur on other planets besides Earth, but it had never been observed until the Trace Gas Orbiter (TGO) satellite did so earlier this year. The Earth's glow can usually be seen from the International Space Station.
“One of the brightest emissions seen on Earth stems from night glow," said the study's lead author, Jean-Claude Gérard of the Université de Liège, Belgium, in a statement. "More specifically, from oxygen atoms emitting a particular wavelength of light that has never been seen around another planet.”
“However, this emission has been predicted to exist at Mars for around 40 years — and, thanks to TGO, we’ve found it,” Gérard added.
The excited oxygen was observed at very precise altitudes, with the strongest reading "at an altitude of around 80 kilometers and varied depending on the changing distance between Mars and the Sun,” one of the study's co-authors, Ann Carine Vandaele, added.
The TGO has been observing the Red Planet since October 2016.
The phenomenon on Earth causes the polar auroras, also known as the Northern and Southern Lights, but this is very different from that, as the planet does not have a magnetic field, researchers noted.
“We modeled this emission and found that it’s mostly produced as carbon dioxide, or CO2, is broken up into its constituent parts: carbon monoxide and oxygen,” Gérard explained. “We saw the resulting oxygen atoms glowing in both visible and ultraviolet light.”
“The observations at Mars agree with previous theoretical models but not with the actual glowing we’ve spotted around Earth, where the visible emission is far weaker,” Gérard continued. “This suggests we have more to learn about how oxygen atoms behave, which is hugely important for our understanding of atomic and quantum physics.”
Gaining additional knowledge about the Martian atmosphere could help researchers better understand where to send future missions to the Red Planet, Håkan Svedhem, ESA’s TGO Project Scientist, said.
“This type of remote-sensing observation, coupled with in situ measurements at higher altitudes, helps us to predict how the martian atmosphere will respond to seasonal changes and variations in solar activity,” Håkan explained. “Predicting changes in atmospheric density is especially important for forthcoming missions, including the ExoMars 2022 mission that will send a rover and surface science platform to explore the surface of the Red Planet.”
The research has been published in the scientific journal Nature Astronomy.
Researchers continue to learn more about the Red Planet, ahead of NASA's long-term goal to send a manned mission to the planet in the 2030s.
A study published in March suggested Mars had two unique reservoirs of ancient water that once flowed deep beneath the planet's surface.
NASA's next mission to Mars involves the recently renamed Perseverance rover on July 20, 2020. The Perseverance rover will attempt to detect if there is any fossilized evidence of extraterrestrial beings, in addition to other tasks.