At Night, the Martian Sky Pulses and Glows When Viewed in Ultraviolet Light

Ultraviolet 'Nightglow' of Mars's amosphere. (Image: NASA/MAVEN/Goddard Space Flight Centre/CU/LASP)
Ultraviolet 'Nightglow' of Mars's amosphere. (Image: NASA/MAVEN/Goddard Space Flight Centre/CU/LASP)

New ultraviolet observations of the Red Planet highlight complex circulation patterns in the Martian atmosphere, including eerily regular nightglow pulses invisible to the unaided eye.

The Martian atmosphere, when viewed through ultraviolet light, is very busy, but only at night, and only during certain seasons, as new research shows. These pulsing and glowing atmospheric effects aren’t fully understood, but their presence reminds us that Mars has a really complicated atmosphere.

The new study, published in the Journal of Geophysical Research, Space Physics, was made possible by the Imaging Ultraviolet Spectrograph (IUVS) instrument on NASA’s MAVEN spacecraft, which has been in orbit around Mars since 2014. UVS provides a completely new lens with which to observe the Red Planet, revealing previously unseen circulation patterns in the Martian atmosphere.

The new paper, led by Nick Schneider from the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, analysed data gathered by the UVS instrument over the course of two consecutive Martian years (a year on Mars is equal to 687 days on Earth). By studying Mars in ultraviolet light, the researchers were able to visualise the effects of global-scale winds and waves high up in the Martian atmosphere.

“MAVEN’s images offer our first global insights into atmospheric motions in Mars’ middle atmosphere, a critical region where air currents carry gases between the lowest and highest layers,” explained Schneider in a NASA press release.

The nightglow as seen at the northern polar region. The cause of the spiral shape remains a mystery. (Image: NASA/MAVEN/Goddard Space Flight Centre/CU/LASP)

These psychedelic actions, known as atmospheric tides, form from a recombination of nitrogen and oxygen atoms in Mars’ nightside mesosphere — the middle layer between the stratosphere and thermosphere. By viewing Mars in UV light, the scientists were able to visualise changes in wind patterns across the different seasons, which influence the atmospheric nightglows. These planet-encircling waves are also influenced by solar heat and topographical disturbances caused by Mars’s massive volcanoes, according to the research.

Indeed, the mountainous volcanic regions on Mars are known to produce some really fascinating and freaky phenomena, including a massive elongated cloud that reappears like clockwork above Arsia Mons, a 19 kilometre high volcano located near the Martian equator.

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“MAVEN’s main discoveries of atmosphere loss and climate change show the importance of these vast circulation patterns that transport atmospheric gases around the globe and from the surface to the edge of space,” explained LASP scientist and study co-author Sonal Jain in the press release.

Interestingly, the atmospheric pulses happen exactly three times each night, but only during the spring and fall. The scientists also documented inexplicable waves and spirals above the winter polar regions, along with some unusually bright spots seen over the winter poles.

Infographic explaining the nightglow phenomenon. (Image: NASA/MAVEN/Goddard Space Flight Centre/CU/LASP)

In these bright areas, gases are thrust downwards by vertical winds, causing them to enter into regions with higher atmospheric density. This serves to accelerate chemical reactions responsible for nitric oxide, which “power the ultraviolet glow,” according to the NASA press release. The UV emissions occur predominantly at altitudes reaching 40 miles (64 kilometers) above the surface, with some patches appearing as large as 600 miles (965 kilometers) in diameter.

These emissions are not to be confused with Mars’s eerie green glow — a visible hue caused by the Sun’s rays exciting oxygen molecules in the upper atmosphere. To a human observer on the Martian ground, these nightly spectacles would be invisible. In future, a possible fun activity for colonists would be to watch these nightglows with UV goggles, in a sky-watching pastime roughly analogous to viewing the Northern Lights on Earth. This would apparently be quite the spectacle, as these bright patches zip across the Martian night sky at speeds reaching 180 mph (290 kph).