Astronomers Detect a Fascinating Green Glow in The Atmosphere of Mars

Substantial in the atmosphere of Mars, astronomers have discovered a phenomenon they’ve been hunting for decades: a faint environmentally friendly glow, brought on by the interaction involving daylight and oxygen in the higher atmosphere.


Formerly, this glow has only been detected in a single area: the sky above Earth. Its discovery in the Martian atmosphere will aid us greater comprehend the procedures that generate airglow, both equally on Earth and in other places.

“1 of the brightest emissions noticed on Earth stems from night time glow. A lot more particularly, from oxygen atoms emitting a particular wavelength of light-weight that has never been noticed around a further earth,” explained astronomer Jean-Claude Gérard of the Université de Liège in Belgium, the direct author of the new paper describing the phenomenon.

“On the other hand, this emission has been predicted to exist at Mars for around 40 a long time – and, many thanks to [ExoMars Trace Gas Orbiter], we have discovered it.”

Earth’s sky is never wholly darkish, not even at night time, even after you have extracted light-weight pollution, starlight, and diffuse daylight. The molecules in the atmosphere are consistently going through a variety of procedures, which brings about them to faintly glow throughout a array of wavelengths.

The glow is not dissimilar to aurora, given that it can be generated by the very same particles – other than it can be considerably fainter, and the mechanisms guiding it are different. Aurora is generated by charged particles from the solar wind which ionise atmospheric atoms, causing them to kind dancing lights throughout the sky.


Airglow, on the other hand, is brought on by the interaction involving daylight and the atmosphere, and falls broadly into two types. There is nightglow this occurs when atoms damaged aside by solar radiation for the duration of the working day recombine, releasing their extra electricity in the kind of photons. Nightglow has earlier been noticed on both equally Venus and Mars, as properly as Earth.

What astronomers have now noticed in the atmosphere of Mars is dayglow – a phenomenon which is considerably more durable to detect, presented that its faint existence is vastly outshone by wide daylight.

On Earth, it occurs when molecules in the atmosphere absorb daylight, which presents them extra electricity they emit in the kind of radiation at the very same or a bit reduce frequency as the radiation absorbed in the first area.

In photos of Earth taken from the Intercontinental Space Station, when the digital camera is wanting throughout the leading of the atmosphere rather than straight down, the airglow is considerably more noticeable.

On the Purple World, such dayglow was predicted in 1979, but Mars orbiters, facing straight at the Martian area, had failed to detect it right up until now.

nightglowEarth’s nightglow. (NASA)

So, studying from the ISS, the workforce reoriented the Nadir and Occultation for MArs Discovery (NOMAD) instrument from its situation wanting straight down at Mars, to wanting throughout the atmosphere in the direction of the Martian horizon. From this situation, they took a array of observations of the Martian atmosphere, at a array of altitudes involving 20 and 400 kilometres (twelve to 250 miles).

When they analysed the facts, they discovered the environmentally friendly emission in both equally optical and ultraviolet wavelengths, in all of the dayside observations.


“The emission was strongest at an altitude of around 80 kilometres and various based on the switching distance involving Mars and the Sunlight,” defined planetary aeronomer Ann Carine Vandaele of the Institut Royal d’Aéronomie Spatiale de Belgique in Belgium.

When the workforce modelled the system guiding the emission, they discovered that it can be generated by a system very similar to airglow on Earth. When solar radiation hits the Martian atmosphere, it splits aside carbon dioxide into carbon monoxide and oxygen. It is really the oxygen atoms that are dependable for the environmentally friendly glow.

But there was a thing intriguing, as well. The emission’s noticeable wavelength was 16.five times more intensive than its ultraviolet wavelength.

“The observations at Mars agree with previous theoretical versions but not with the precise glowing we have noticed around Earth, in which the noticeable emission is considerably weaker,” Gérard explained.

“This suggests we have more to find out about how oxygen atoms behave, which is hugely vital for our understanding of atomic and quantum physics.”

This discrepancy, the workforce notes, could be an problem with the way the instrument getting Earth observations has been calibrated. Naturally the greatest point to do is a entire whole lot more science.

The research has been posted in Character Astronomy.