The MAVEN space probe discovered an aurora and a mysterious dust cloud on Mars

Map of the aurora detected by the MAVEN space probe overlaid on Mars' surface (Image University of Colorado)
Map of the aurora detected by the MAVEN space probe overlaid on Mars’ surface (Image University of Colorado)

At the 46th Lunar and Planetary Science Conference being held in The Woodlands, Texas, some surprising discoveries made on Mars thanks to NASA’s space probe MAVEN (Mars Atmosphere and Volatile Evolution) were presented. They’re a cloud of dust at high altitudes and an aurora that goes deep into the Martian atmosphere.

The dust cloud was detected by the LPW (Langmuir Probe and Waves) instrument of the MAVEN spacecraft at altitudes between 150 and 300 km (93 and 190 miles) with a very low density that gets even lower at higher altitudes. Its presence is unexpected and it’s unclear whether this is a temporary phenomenon or a long-term one. MAVEN detected it throughout its operating time, started after its arrival in Mars orbit in September 2014.

There are a few theories to explain the origin of this dust cloud. It could come from Mars moons Phobos and Deimos. It could be dust moving in the solar wind coming from the Sun. It could be debris from comets captured by Mars while orbiting around the Sun.

The problem is that none of the known processes on Mars may explain the appearance of that dust from those sources in the observed areas. It’s for this reason that Laila Andersson of the University of Colorado’s Laboratory for Atmospherics and Space Physics (CU LASP) commented that if the dust comes from the atmosphere that means that we don’t know some fundamental process of the Martian atmosphere.

The IUVS (UltraViolet Imaging Spectrograph) instrument of the MAVEN spacecraft observed what was called “Christmas Lights”. For five days before December 25, MAVEN saw ultraviolet aurora along the northern hemisphere of Mars. The surprising aspect is the depth in the atmosphere it happened, much greater than on Earth or in other areas of Mars.

On Earth, the aurora occurs near the poles and is caused by high energy particles such as electrons that hit the atmosphere causing the glow of the gas that makes it up. Arnaud Stiepen, IUVS team member at the University of Colorado, commented that the electrons that cause the aurora observed by MAVEN last December must be really energetic.

The SEP (Solar Energetic Particle) instrument of the MAVEN spacecraft detected a significant increase of energetic electrons when the aurora appeared. Considering that the solar energetic particles are called that way because they come from the Sun, our star seems to be the cause of that aurora.

Those electrons can be very energetic and therefore penetrate into the depths of Mars atmosphere because the planet has no magnetic field. The Earth is protected by a shield formed by its magnetic field, which prevents most of the energetic electrons from penetrating into the atmosphere.

Despite the vast number of space probes, landers and rovers sent to Mars, the red planet keeps on giving us surprises. On the other hand, it’s precisely because scientists are aware that there’s still much to discover that new missions keep on being planned.

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