Scientists using the Imaging Ultraviolet Spectrograph (IUVS) instrument on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have observed a bright ultraviolet auroral glow spanning the northern hemisphere of the Red Planet.
Martian aurora is similar to Earth’s Aurora borealis but has a different origin. Image credit: University of Colorado.
“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 team member Arnaud Stiepen of the University of Colorado.
“The electrons producing it must be really energetic. The source of the energetic particles appears to be the Sun.”
MAVEN’s Solar Energetic Particle (SEP) instrument detected a huge surge in energetic electrons at the onset of the aurora.
Billions of years ago, the planet lost a global protective magnetic field like Earth has, so solar particles can directly strike the atmosphere.
The electrons producing the aurora have about hundred times more energy than you get from a spark of house current, so they can penetrate deeply in the atmosphere.
Using another instrument aboard MAVEN, the Langmuir Probe and Waves (LPW), the scientists observed an unexplained high-altitude dust cloud in the Martian atmosphere. The presence of the dust at orbital altitudes from about 93 miles (150 km) to 190 miles (300 km) above the surface was not predicted.
“If the dust originates from the atmosphere, this suggests we are missing some fundamental process in the Martian atmosphere,” said team member Laila Andersson, also from the University of Colorado.
It is unknown if the cloud is a temporary phenomenon or something long lasting. The cloud density is greatest at lower altitudes. However, even in the densest areas it is still very thin. So far, no indication of its presence has been seen in observations from any of the other MAVEN instruments.
Possible sources for the observed dust include dust wafted up from the atmosphere; dust coming from Phobos and Deimos, the two moons of Mars; dust moving in the solar wind away from the sun; or debris orbiting the sun from comets. However, no known process on Mars can explain the appearance of dust in the observed locations from any of these sources.
The results were presented this week at the 46th Lunar and Planetary Science Conference in The Woodlands, TX.
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