For five days before Dec. 25, Mars gave NASA scientists a Christmas light show. NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft detected an ultraviolet glow in the planet's northern hemisphere.
Earth is no stranger to this phenomenon. On Tuesday, unusually high solar flare activity had people spotting auroras as far south as the Northern United States, but the display caused by high-energy particles interacting with Earth's atmosphere is more common in the polar regions.
But they're a little different on Mars.
"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,” Arnaud Stiepen, a MAVEN team member at the University of Colorado, said in a statement. “The electrons producing it must be really energetic."
Earth has a magnetic field that protects the inner atmosphere from space's radiation. When we see auroras on our planet, it's because some of the sun's energetic particles have managed to break through it. Mars lost its magnetosphere billions of years ago, so solar particles can hit the atmosphere directly and penetrate deeper.
Less pretty (but possibly even more intriguing) is a dust cloud also detected by MAVEN. While the aurora was unexpectedly deep in the atmosphere, the dust cloud was at an unexpectedly high altitude -- about 93 miles to 190 miles above the surface.
The cloud has been present the whole time MAVEN has been operating, and NASA representatives say it doesn't pose a threat to any of the spacecraft orbiting the Red Planet. But it's not clear yet whether it's a temporary thing or a long-lasting phenomenon, because MAVEN has only been in orbit for four months. There are several places the dust could come from -- Mars's two moons, solar wind, or comet debris, for starters -- but scientists don't know how exactly it got there.
MAVEN has another eight months left in its primary mission, so hopefully more data will help solve the mystery.