Spacecraft detects strange never-before-seen green glow on Mars

The Exomars orbiter detected a glow above Mars (ESA)

An orbiting spacecraft has detected a strange green glow on Mars that had previously only been seen on one planet – Earth.

The ExoMars Trace Gas Orbiter (TGO) spotted glowing green oxygen in Mars's atmosphere similar to the northern lights seen on Earth.

It's something scientists had been hunting for four decades until the European Space Agency (ESA) satellite spotted it, according to a study published in Nature Astronomy.

The Exomars orbiter detected a glow above Mars (ESA)

On Earth, glowing oxygen is produced during polar auroras when energetic electrons from interplanetary space hit the upper atmosphere, creating a distinctive green glow.

But the atmospheres of Earth and Mars also glow constantly during both day and night as sunlight interacts with atoms and molecules within the atmosphere.

On Earth, green night glow is quite faint, but is visible in some of the spectacular images taken by astronauts aboard the International Space Station (ISS).

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Images from the surface of Mars
In this image taken by Curiosity's Mast Camera, the Alpha Particle X-Ray Spectrometer (APXS) on NASA's Curiosity rover is pictured, with the Martian landscape in the background on the 32nd Martian day, or sol, of operations on the surface on September 7, 2012, PDT or September 8, 2012, UTC. This image lets researchers know that the APXS instrument had not become caked with dust during Curiosity's dusty landing. Scientists enhanced the color in this version to show the Martian scene as it would appear under the lighting conditions we have on Earth, which helps in analyzing the terrain. REUTERS/NASA/JPL-Caltech/MSSS/Handout (UNITED STATES - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
An image from the Mast Camera (Mastcam) on NASA's Mars rover Curiosity shows the surface of the planet with inclined layering known as cross-bedding in an outcrop called "Shaler" on a scale of a few tenths of a meter, or decimeters (1 decimeter is nearly 4 inches) in this NASA handout released January 15, 2013. REUTERS/NASA/JPL-Caltech/MSSS/Handout (OUTERSPACE - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
NASA's Curiosity Mars Rover snaps a self-portrait at a site called Vera Rubin Ridge on the Martian surface in February 2018 in this image obtained on June 7, 2018. Courtesy NASA/JPL-Caltech/MSSS/Handout via REUTERS ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY.
An image taken by the Mars Reconnaissance Orbiter (MRO) and released March 29, 2017 shows a mound that appears to have blocked the path of dunes as they move south (north is to the left in this image). NASA/JPL/University of Arizona/Handout via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY
A view of the surface of Mars released by NASA on March 7, 2017, shows viscous, lobate flow features commonly found at the bases of slopes in the mid-latitudes of Mars, and are often associated with gullies. These are bound by ridges that resemble terrestrial moraines, suggesting that these deposits are ice-rich, or may have been ice-rich in the past. NASA/JPL-Caltech/Univ. of Arizona/Handout via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY
Portions of the Martian surface shot by NASA's Mars Reconnaissance Orbiter show many channels from 1 meter to 10 meters wide on a scarp in the Hellas impact basin, in this photograph taken January 14, 2011 and released by NASA March 9, 2011. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. Researchers found telltale fingerprints of salts that form only in the presence of water in narrow channels cut into cliff walls throughout the planet's equatorial region. REUTERS/NASA/JPL-Caltech/Univ. of Arizona/Handout FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
Dark, narrow, 100 meter-long streaks on Mars inferred to have been formed by contemporary flowing water are seen in an image produced by NASA, the Jet Propulsion Laboratory (JPL) and the University of Arizona. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. NASA/JPL/University of Arizona/Handout THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
NASA's Mars rover Curiosity's hole drilled into a rock target, "Cumberland," on Mars on May 19, 2013 is shown in this NASA photo. NASA?s Mars rover Curiosity has found carbon-containing compounds in samples drilled out of an ancient rock, the first definitive detection of organics on the surface of Earth?s neighbor planet, scientists said on Tuesday. REUTERS/NASA/Handout (OUTER SPACE - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
NASA's Mars Exploration Rover Opportunity is shown in this handout photo released to Reuters July 29, 2014. Opportunity has set a new off-Earth, off-road distance record, logging just over 25 miles (40 km) on the surface of the Red Planet to surpass the old benchmark set in 1973 by a Russian probe on the moon. REUTERS/NASA/JPL-Caltech/Cornell Univ./Arizona State University/Handout (UNITED STATES - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
A billion-pixel view from the surface of Mars, from NASA's Mars rover Curiosity, offers armchair explorers a way to examine one part of the Red Planet in great detail is shown in this composite produced using 850 frames from the telephoto camera of Curiosity's Mast Camera instrument, 21 frames from the Mastcam's wider-angle camera and 25 black and white frames of the rover itself from the Navigational Camera. The photos were taken between October 5 and November 16, 2012. REUTERS/NASA/JPL-Caltech/MSSS/Handout via Reuters (OUTERSPACE - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
The surface of the planet Mars inside Gale's Crater is shown as NASA's Mars rover Curiosity drives toward a flat rock with pale veins that may hold clues to a wet history on the planet in this NASA handout photo released January 15, 2013. If the rock meets rover engineers' approval when Curiosity rolls up to it in coming days, it will become the first to be drilled for a sample during the Mars Science Laboratory mission. REUTERS/NASA/Handout (OUTERSPACE - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
A rock outcrop called Link pops out from a Martian surface in this NASA handout image taken by the 100-millimeter Mast Camera on NASA's Curiosity Mars rover September 2, 2012 and released September 27, 2012. Rounded gravel fragments, or clasts, up to a couple inches (few centimeters) in size are in a matrix of white material. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. Scientists enhanced the color in this version to show the Martian scene as it would appear under the lighting conditions we have on Earth, which helps in analyzing the terrain. REUTERS/NASA/JPL-Caltech/MSSS/Handout (UNITED STATES - Tags: SCIENCE TECHNOLOGY) THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
The left eye of the Mast Camera (Mastcam) on NASA's Mars rover Curiosity took this image of the camera on the rover's arm, the Mars Hand Lens Imager (MAHLI), during the 30th Martian day, or sol, of the rover's mission on Mars on September 5, 2012. The image shows that MAHLI has a thin film or coating of Martian dust on it. This dust accumulated during Curiosity's final descent to the Martian surface, as the Mars Science Laboratory spacecraft's descent stage (or sky crane) engines were disrupting the surface nearby. Effects of the dust were seen in the first image takenof Mars by MAHLI, on the day after landing. The mechanism at the right in this image is Curiosity's dust removal tool, a motorized wire brush. REUTERS/NASA/JPL-Caltech/MSSS/Handout (UNITED STATES - Tags: ENVIRONMENT SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
A cropped image from NASA's Curiosity rover shows one set of marks on the surface of Mars where blasts from the descent-stage rocket engines blew away some of the surface material in NASA handout photo released to Reuters, August 17, 2012. REUTERS/NASA/JPL-Caltech/MSSS (UNITED STATES - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
This color image taken August 8, 2012 from NASA's Curiosity rover, and released August 13, shows part of the wall of Gale Crater, the location on Mars where the rover landed on August 5, 2012. This is part of a larger, high-resolution color mosaic made from images obtained by Curiosity's Mast Camera. This image of the crater wall is north of the landing site, or behind the rover. Here, a network of valleys believed to have formed by water erosion enters Gale Crater from the outside. This is the first view scientists have had of a fluvial system - one relating to a river or stream from the surface of Mars. REUTERS/NASA/JPL-Caltech/MSSS/Handout (SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
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This green glow has now been detected for the first time on Mars by the ExoMars TGO, which has been orbiting Mars since October 2016.

Jean-Claude Gerard, of the Universite de Liege in Belgium, said: "One of the brightest emissions seen on Earth stems from night glow.

"More specifically, from oxygen atoms emitting a particular wavelength of light that has never been seen around another planet.

"However, this emission has been predicted to exist at Mars for around 40 years – and, thanks to TGO, we've found it."

Similar airglow seen from the International Space Station (NASA)

Gerard and colleagues were able to spot this emission using a special observing mode.

One of the orbiter's advanced suite of instruments, known as NOMAD (Nadir and Occultation for Mars Discovery) and including the ultraviolet and visible spectrometer (UVIS), can observe in various configurations, one of which positions its instruments to point directly down at the martian surface – also referred to as the 'nadir' channel.

Co-author Ann Carine Vandaele, of the Institut Royal d'Aeronomie Spatiale de Belgique, said: "Previous observations hadn't captured any kind of green glow at Mars, so we decided to reorient the UVIS nadir channel to point at the 'edge' of Mars, similar to the perspective you see in images of Earth taken from the ISS.

"The emission was strongest at an altitude of around 80 kilometres and varied depending on the changing distance between Mars and the Sun."

This understanding is key to characterising planetary atmospheres and related phenomena – such as auroras.

By deciphering the structure and behaviour of this green glowing layer of Mars' atmosphere, scientists can gain insight into an altitude range that has remained largely unexplored, and monitor how it changes as the Sun's activity varies and Mars travels along its orbit around our star.

- This article first appeared on Yahoo

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