It seems that despite the fact that humanity has had orbiters in the sky and landers on the Martian surface since the 1970s, the Red Planet is still full of surprises. A new Mars orbiter sent by NASA has now noticed not one, but two unexpected phenomena in the planet's atmosphere: an unexplained high-altitude dust cloud and an unusual aurora.
The dust cloud alone adds to the atmosphere's reputation as an enigma, especially after a mysterious atmospheric blob grew so large that it was noticed by the lenses of countless amateur astronomers and private observatories in 2012.
NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft observed the dust cloud at orbital altitudes ranging from about 93 miles (150 kilometers) to 190 miles (300 kilometers) above the Red Planet's surface - a natural event that was not expected under experts' current understanding of Martian weather patterns.
"If the dust originates from the atmosphere, this suggests we are missing some fundamental process in the Martian atmosphere," Laila Andersson, of the University of Colorado's Laboratory for Atmospherics and Space Physics (CU LASP), explained in a statement.
Interestingly, MAVEN's Langmuir Probe and Waves (LPW) instrument has been watching the dust cloud ever since the craft first slipped into Martian orbit in 2014, but despite its density, it appears that other MAVEN instruments and even other orbiters are having trouble noticing it. Experts aren't even sure if the cloud is temporary or here to stay.
Even more baffling is the fact that no known process on Mars can explain the appearance of dust in the observed locations, nor do other probable sources - such as dust coming from the moons Phobos and Deimos - explain how it got there.
Additionally, it appears that Mars also plays host to its own unique brand of aurora. MAVEN's array of instruments managed to pick up what experts are calling the "Christmas lights," in the Martian atmosphere five days before Dec. 25. The lights - a bright ultraviolet display - was caused by what appears to be an aurora, but one that is acting rather strangely. (Scroll to read on...)
"What's especially surprising about the aurora we saw is how deep in the atmosphere it occurs - much deeper than at Earth or elsewhere on Mars," said Arnaud Stiepen, who works with the orbiters Imaging Ultraviolet Spectrograph (IUVS).
Traditionally, auroras are caused by a complex interplay between charged solar particles, a planet's (or moon's) magnetosphere, and atmospheric gases that glow when heated.
Stiepen explained that for the phenomenon to reach so deep into Martian airspace, the particles that caused the aurora "must be really energetic" - unusually so.
The experts add that this could just be an example of how vulnerable the Red Planet is now to solar activity, as it has been suggested in the past that it was once stripped of a thicker atmosphere in the wake of an exceptionally powerful wave of solar winds - an event that has left the planet with a mere 13 percent of the water it once had.
This may have in-part occurred because the Martian magnetosphere is notably weaker than Earth's, allowing the electrons involved in the Christmas lights aurora to produce about 100 times more energy than you get from a spark of everyday house current, Stiepen and his colleagues determined.
These findings and others are being presented alongside the appropriate data at the 46th Lunar and Planetary Science Conference in The Woodlands, Texas this week.
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