Mars continues to hold surprises for the exploratory craft that now orbit it and traverse its dusty surface.
The latest discovery is from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, which detected an unexplained high-altitude dust cloud and an aurora that reaches deep into the Red Planet’s atmosphere.
The dust is present as far as 93 miles (150 kilometers) to 190 miles (300 kilometers) above the surface. The dust is at orbital altitudes, but is not a hazard to MAVEN and other spacecraft now orbiting Mars.
The MAVEN Langmuir Probe and Waves instrument discovered the dust, which has been present the whole time the craft has been orbiting Mars. It is unknown whether the cloud is a temporary phenomenon or something long lasting. The density of the cloud is greater at lower altitudes, but still very thin. None of the other MAVEN instruments has been able to detect the dust.
According to Laila Andersson of the University of Colorado’s Laboratory for Atmospherics and Space Physics (CU LASP), in Boulder, Colorado, “If the dust originates from the atmosphere, this suggests we are missing some fundamental process in the Martian atmosphere.”
There are a number of possible explanations for the dust cloud. It could be dust wafting up from the planet’s surface, dust coming from the two moons of Mars, dust moving in the solar wind, or debris from comets. However, no known process on Mars can explain the appearance of dust in the observed locations from any of these sources.
The Imaging Ultraviolet Spectrograph (IUVS) of the MAVEN spacecraft observed the Aurora, which spans the northern hemisphere of Mars, for five days just before December 25. MAVEN was launched on November 18, 2013 and arrived at Mars on September 21.
Auroras are caused by energetic particles like electrons crashing down into the atmosphere resulting in the glow of gas.
Armaud Stiepen, IUVS team member at the University of Colorado, noted that scientists are surprised by how deep the aurora is in the atmosphere, “… it is much deeper than at Earth or elsewhere on Mars,” he said.
So far it appears that the sun is the source of the energetic particles. MAVEN’s Solar Energetic Particle instrument detected a huge surge in energetic electrons at the onset of the aurora. Mars lost a global protective magnetic field like Earth billions of years ago. So it is possible for solar particles to directly strike the atmosphere. The electrons producing the aurora have about 100 times more energy than a spark of house current. So they can penetrate deep into the atmosphere.
MAVEN is part of NASA’s Mars Exploration Program, which includes the rovers, Opportunity and Curiosity, and the Mars Odyssey and Mars Reconnaissance Orbiter spacecraft now orbiting the planet.
MAVEN’s primary mission will last for one Earth-year.
NASA is currently developing the human spaceflight capabilities needed for a journey to Mars, which is scheduled for some time in the 2030’s.