New data from the National Aeronautics and Space Administration's (Nasa) Maven spacecraft has shown vast areas of the Martian night sky pulsing in ultraviolet light.
However, do not expect the future Mars astronauts to see them with naked eyes as ultraviolet light is invisible to the human eye but detectable by specialized instruments.
The new results, published in the Journal of Geophysical Research — Space Physics, are being used to illuminate complex circulation patterns in the Martian atmosphere.
The Maven team was surprised to find that the atmosphere pulsed exactly three times per night, and only during Mars' spring and autumn.
The new data also revealed unexpected waves and spirals over the winter poles, while also confirming the Mars Express spacecraft results that this nightglow was brightest over the winter polar regions.
"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," said lead author of the paper Nick Schneider of the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP), Boulder, Colorado.
The brightenings occur where vertical winds carry gases down to regions of higher density, speeding up the chemical reactions that create nitric oxide and power the ultraviolet glow.
"The ultraviolet glow comes mostly from an altitude of about 70 kilometers, with the brightest spot about a thousand kilometers across, and is as bright in the ultraviolet as Earth's northern lights," said Zac Milby, also of the LASP.
"Unfortunately, the composition of Mars' atmosphere means that these bright spots emit no light at visible wavelengths that would allow them to be seen by future Mars astronauts. Too bad: the bright patches would intensify overhead every night after sunset, and drift across the sky at 300 km per hour."
The pulsations reveal the importance of planet-encircling waves in the Mars atmosphere, said the study.
The number of waves and their speed indicates that Mars' middle atmosphere is influenced by the daily pattern of solar heating and disturbances from the topography of planet's huge volcanic mountains..
