Will Mars look like this at night to the first humans on Earth? (Photo: NASA/JPL/Maize/Ariz/Knutsen/SWNS)

An eerie green glow has been discovered on the nightside of the Red Planet, but unfortunately not from street lights on Mars.

However, the illumination could be enough to pave the way for future astronauts, as the glow could be as bright as moonlit clouds on Earth.

The mysterious aura was discovered by the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) mission.

“As future astronauts explore the polar regions of Mars, they will see a green glow in the night sky,” ESA said.

“Under a clear sky, the glow can be bright enough for people to see past and rovers to navigate in the dark night.”

‘Night glow is also observed on Earth.’ “On Mars it was something that was expected but had never been seen in visible light before.”

Although nocturnal glows can be seen on our planet, they should not be confused with aurorae, which are created when high-energy electrons from the Sun hit the upper layers of the atmosphere.

ESA’s ExoMars Trace Gas Orbiter detects the green glow of oxygen in the Martian atmosphere (artist’s impression) (Photo: ESA/SWNS)

But the nighttime glow on Mars is actually the result of a dizzying journey through the planet’s rare oxygen supplies.

During the day on Mars, sunlight excites carbon dioxide molecules, causing them to break down into their individual atoms: one carbon and two oxygen atoms.

As the loose oxygen atoms migrate to the nightside, pairs combine to form an oxygen molecule that emits a green glow as it appears about 50 kilometers above the surface.

“These observations are unexpected and interesting for future trips to the Red Planet,” said Professor Jean-Claude Gérard, lead author of the new study and a planetary scientist at the University of Liège.

How the green glow is created

During the day, carbon dioxide molecules are broken down and converted into oxygen molecules at night, creating a green glow (Photo: ESA)

The international science team was intrigued by an earlier discovery made with Mars Express, where nightglows were observed in the infrared wavelength range a decade ago.

The Trace Gas Orbiter followed in 2020, discovering glowing green oxygen atoms high above the dayside of Mars – the first time this daylight emission has been observed around a planet other than Earth.

The night glow serves as an indicator of atmospheric processes. It can provide a wealth of information about the composition and dynamics of a difficult-to-measure region of the atmosphere, as well as about oxygen density. It can also show how energy is deposited by both sunlight and the solar wind – the stream of charged particles coming from our star.

Airglow in the Earth's atmosphere

Airglow is created in Earth’s atmosphere when sunlight interacts with atoms and molecules in the atmosphere (Photo: NASA/SWNS)

Understanding the properties of Mars’ atmosphere is not only scientifically interesting, but also crucial for missions to the Red Planet’s surface.

For example, atmospheric density directly affects the drag experienced by orbiting satellites and the parachutes used to deliver probes to the surface of Mars.

Both night lights and auroras can have a wide range of colors depending on which atmospheric gases are most prevalent at different altitudes.

“The green night light on our planet is quite dim, so it is best seen from a side perspective, as shown by many spectacular images taken by astronauts from the International Space Station,” ESA said.

The study was published in the journal Nature Astronomy.