The green glow on Mars

The red planet … and green. You could say that about Mars these days. A strange green halo appeared on the surface of Mars. It was captured by the satellite for the investigation of trace gases (TGO). It is part of the ExoMars mission of the European Space Agency (ESA). It has been orbiting Mars since 2016 to learn more about our neighbor’s atmosphere. It is the first time that it was discovered on a planet other than Earth. The green glow on Mars marks a relevant spatial milestone.

The green glow on Mars, something that was never discovered on a planet other than Earth.
The green glow on Mars, something that was never discovered on a planet other than Earth.
Never seen on another planet before

“One of the brightest emissions observed on Earth comes from night light. It comes from oxygen atoms that emit a certain wavelength of light. It has never been seen on another planet.” Jean-Claude Gérard from the University of Liège, Belgium, says this. He is the lead author of the new study published in Nature Astronomy. “However, this emission is expected to exist on Mars for around 40 years. Thanks to TGO, we found it, »he explains in a statement.

Oxygen shines on Earth during the polar aurors. It is when charged electrons from space collide with the atmosphere. The emission of light by oxygen gives the polar aurors their characteristic greenish hue. However, the aurora is just one of the ways that planet atmospheres glow. With planets like Earth and Mars, the luminescence is constant day and night. Day and night flashes are due to slightly different mechanisms. The nocturnal ones arise when decomposed molecules are recombined. During the day, when sunlight directly stimulates atoms and molecules such as nitrogen and oxygen.

Lateral view

The green night light is very weak on Earth. The best thing is to see it across. This is shown by numerous spectacular images taken by astronauts on board the International Space Station (ISS). Weakness of light can be a problem when searching on other planets.

The glow had only been seen on Earth.
The glow had only been seen on Earth.

Gérard and his colleagues were able to recognize the green glow on Mars from the special observation of the TGO. «Previous observations hadn’t caught any green glow on Mars. We have decided to realign the Nadir UVIS channel to target the “edge” of Mars. Similar to the perspective seen in images of the Earth from the ISS, ”adds co-author Ann Carine Vandaele. It is from the Institut Royal d’Aéronomie Spatiale de Belgique, Belgium.

Studying the shine of the planet’s atmosphere can provide a lot of information. For example the composition and dynamics of an atmosphere. Or show how energy from sunlight and solar wind is deposited.

Understanding the properties of the Martian atmosphere is not only of scientific interest. It is important to carry out the missions that will be sent to the Red Planet in the medium term. For example, atmospheric density has a direct impact on the resistance that satellites orbit. And for the parachutes with which probes were placed on the surface of Mars.

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