Mars has an eerie green glow of oxygen and it could be the key to unlocking seasons on the Red Planet

• European Space Agency’s (ESA) ExoMars Trace Gas Orbiter (TGO) has spotted a green glow of oxygen around the Red Planet.
  
• This makes Mars the only other planet, other than Earth, to host auroras.
  
• The presence of oxygen doesn’t mean humans will be able to breathe on Mars but it will give astronomers more insight on seasonal changes occur as sunlight interacts with different particles.
  

Mars is the only planet in the universe, other than Earth, where astronomers have been able to spot an eerie green glow of oxygen.


Spotted by the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter only recently, astronomers believe this emission that existed around Mars for at least the past 40 years.

On Earth, we know this green glow as polar auroras or the ‘northern lights’. This is when energetic electrons from interplanetary space hit the planet’s upper atmosphere. It’s known to be more pronounced during events like solar flares since more electrons hit the planet’s atmosphere.

However, the aurora is just one way in which planetary atmospheres can light up. Planets like Earth and Mars glow constantly — both during the day and at night — as sunlight interacts with different molecules.

Seen from outer space, Earth’s green flow is actually quite faint. It can be best spotted when looking at the planet from an ‘edge on’ perspective.

Does this mean that we can breathe on Mars?
Unfortunately, the discovery of the green glow around Mars doesn’t mean that humans will be able to breathe on Mars. "We modelled 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," said Jean-Claude, the lead author of the study published in Nature Astronomy.

"We saw the resulting oxygen atoms glowing in both visible and ultraviolet light," he added explaining how the two kinds of emission showed that the visible emission was 16.5 times more intense than the ultraviolet emissions.

So, while it may not mean that the atmosphere is breathable, it still contains a wealth of information for when humans eventually do plan to land on the Red Planet.

It can explain the composition and dynamics of the atmosphere, how energy is deposited by sunlight and solar winds, and how Mars’ atmosphere gets its characteristics — like auroras.

Mars and its seasons
"The emission was strongest at an altitude of around 80 kilometres and varied depending on the changing distance between Mars and the Sun," said Ann Carine, co-author of the study.

By understanding how the structure and behaviour of this green glowing layer of Mars’ atmosphere changes, astronomers can predict the planet’s seasonal changes with variations in solar activity.

Understanding how the atmosphere changes is important for future missions. The density, for example, directly affects the pull felt by orbiting satellites and by parachutes trying to land probes on the Red Planet’s surface.

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