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“Invisible” Auroras Mapped on Mars

Earth isn’t the only planet that puts on a flashy light show.


Last week Saturn was the exhibitionist, showing off a vibrant blue aurora around its northern polar hexagon. And Jupiter made the crowds cheer in 2007 with a shot of its “hyper-auroras” lighting up both poles.

—Photo by Bruce Dale/NGS

Not to be outdone, Mars is the headliner this week. A team using ESA‘s Mars Express orbiter used a combination of onboard instruments to track nine auroral emissions on the red planet.

Their data allowed the team to draw the first map of auroras on Mars, showing that the events coincide with regions on Mars that have the strongest magnetic fields.


An artist’s impression of auroras on Mars’s night side

—Image courtesy M. Holmström (IRF)/ESA

Auroras on Mars are pretty unusual cases, because unlike Earth and the gas giants, Mars no longer has an internal dynamo generating a planet-wide magnetic field.

On Earth it’s the magnetic field lines that channel streams of charged particles from the sun through the atmosphere, getting molecules all excited and causing them to emit light in the form of breathtaking auroral displays.

What Mars has are sections of the crust that were somehow magnetized, and the teams thinks it could be these regions that are attracting streams of particles, allowing auroras to occur.

The trick is that Mars’s thin atmosphere is low in oxygen and molecular nitrogen, which are the elements that create visible light in Earthly auroras.

The Mars Express team’s instruments see only in ultraviolet and so can’t tell if any future human missions to Mars would be in for a show.

“There’s now a large domain of physics that we have to explore in order to understand the aurorae on Mars,” noted team member Francois Leblanc of France’s Service d’Aéronomie.