NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has detected two unexpected phenomena in the short time since making orbit around the red planet – an aurora occurring deep in the Martian atmosphere, and an as of yet unexplained high altitude dust cloud. MAVEN is currently four months into a primary mission lasting one Earth year, during which time it is attempting to shed light on the characteristics of the Martian upper atmosphere and ionosphere, studying how they interact with our Sun.
The composition of the cloud detected by MAVEN's Langmuir Probe and Waves (LPW) instrument is unknown, with no processes currently understood to be taking place on the Red Planet able to account for the existence of the cloud at its present altitude. Furthermore, NASA is uncertain as to whether the cloud is a transient or a long term phenomenon, as it has existed in the Martian atmosphere since the probe gained orbit around the planet on September 21.
MAVEN and other agency assets, such as the Mars Reconnaissance Orbiter, are under no threat from the cloud, which exists at an altitude of between 93 miles (150 km) to 190 miles (300 km) above the Martian surface.
NASA is currently working with three theories regarding the creation of the enigmatic cloud. It is possible that the dust may be constituted of materials from the surface of Mars itself, somehow thrown high into the atmosphere. Conversely there are theories that the material was transferred from one of the planet's moons, Phobos and Deimos. The third possibility is that the dust originated as debris from comets orbiting the Sun, which were then carried into the planet's atmosphere by the solar winds.
While much of the Martian atmosphere has been lost, the desolate planet is still capable of hosting an aurora. The phenomenon occurs when charged particles interact with the planet's atmosphere, causing the gas present there to glow, resulting in a stunning display.
The most recent aurora was detected by MAVEN's Imaging Ultraviolet Spectrograph (IUVS) as a bright ultraviolet glow in the northern hemisphere of Mars. Due to the timing of its appearance, it was given the moniker "Christmas lights," as they appeared in the five days proceeding December 25 2014.
"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," states Arnaud Stiepen, a member of the team that created MAVEN's IUVS instrument at the University of Colorado. "The electrons producing it must be really energetic."
MAVEN will continue to observe the phenomena as it progresses with its mission to unlock the secrets of the Martian atmosphere.