One of the brightest emissions on Earth is a night glow, from a wavelength of light emitted by oxygen that hasn't been seen on another planet.

Artist's impression of the TGO at Mars. The TGO detects the excited oxygen not with an imaging camera (hence no pretty pictures) but with its Nomad spectrometer package. This instrument sees the oxygen at very particular altitudes. Image: ESA

Astronomers have identified a green glow in the Martian atmosphere, not unlike the glow observed by astronauts from the space station when they look towards the Earth.

According to a BBC report, the glow comes from oxygen atoms when they get excited by sunlight. While it has long been predicted to occur on other planets, the Trace Gas Orbiter (TGO), which is a joint European-Russian satellite at Mars, is the first to make the observation outside Earth.

"You’d never plan a mission to go look for this kind of thing. Today, we have to be very clear about the science we’re going to do before we get to Mars," Dr Manish Patel from UK's Open University said, speaking about the finding. "But having got there, we thought, ‘well, let’s have a look’. And it worked."

The study's results, published in the journal Nature Astronomy, add that the emissions are a consequence of collisions between atmospheric molecules and charged particles that are racing away from the Sun. On Earth, these interactions are heavily influenced by the planet's strong magnetic field, which pulls the particles down towards the two magnetic poles.

In a statement by the European Space Agency, lead author 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.”

The statement also points out that this emission has been predicted to exist at Mars for around 40 years.