The strange glow on Mars

What’s that? It was detected for the first time. A ground-based device recorded the strange glow on Mars, which painted its night sky green. It was done by the ExoMars Trace Gas Orbiter mission of the European Space Agency (ESA). He orbited Mars and observed the Martian night sky glowing with a green light. And it was visible to the human eye.

This type of night glow is a relatively common phenomenon in the atmospheres of the solar system. Several things can cause our atmosphere to emit its own light at night. But few more than our own Sun.

The strange glow on Mars gives us clues about its atmosphere.
The strange glow on Mars gives us clues about its atmosphere.

Gases and lights

During the day, sunlight separates the molecules in a process called photodissociation. But on the night side of the atmosphere they are far from the Sun’s harsh radiation. There loose atoms can recombine into molecules. Thus they release their excess energy in the form of photons.

Data from the Trace Gas Orbiter were studied, pointing the instruments at the edge of the atmosphere. They looked for signs of nighttime glow in the ultraviolet and visible wavelengths. And they found it. Between altitudes of 40 and 60 kilometers, there was a nightglow visible at the south pole during the Martian winter.

It’s because oxygen atoms transported from the sunny Martian day combine into dioxygen (O2). And they emit a glow in the process, bright enough to be seen from the ground.

The discovery of visible night glow has some interesting scientific inferences. This is because atmospheric glows are markers of atmospheric chemistry, circulation and processes. Mars has a very thin atmosphere. Finding out what’s there would help understand why and where the rest went.

This glow was detectable to the human eye.
This glow was detectable to the human eye.


The strange glow over Mars is not just visually appealing. It is also useful to detect it. ‘These observations pave the way for future global observations of Martian atmospheric circulation. Simpler and lower cost instrumentation can be used. The researchers say this in their article, published in Nature Astronomy.

That can help us understand why some worlds are lovely and habitable, like Earth. And how some end up differently. This is of interest to scientists searching for habitable worlds elsewhere in the galaxy. And, of course, knowing how the atmosphere of Mars works is something that will benefit those future explorers.

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