Auroras on Mars May Cause the Sky to Turn a Glowing Green

Mars is known as the "Red Planet."  But it's not always russet-colored.  Scientists have discovered that when humans go to Mars, they may find that occasionally the planet may have green skies.

In late Dec. 2014, NASA's MAVEN spacecraft detected evidence of widespread auroras in Mars's northern hemisphere. These aurora circled the globe and descended so close to the Martian equator that were they occurring on earth, they would have been over places such as Florida and Texas.

This isn't the first time that aurora have been detected on Mars, though. Ten years ago, the European Space Agency's Mars Express detected an ultraviolet glow coming from "magnetic umbrellas" in the southern hemisphere.

Unlike Earth Mars doesn't have a global magnetic field that envelops the entire planet. Instead, Mars has umbrella-shaped magnetic fields that sprout out of the ground like mushrooms, here and there, but mainly in the southern hemisphere. These umbrellas are remnants of an ancient global field that decayed billions of years ago.

"The canopies of the patchwork umbrellas are where we expect to find Martian auroras," said Nick Schneider, one of the researchers, in a news release. "But MAVEN is seeing them outside these umbrellas, so this is something new."

Auroras occur when energetic particles from space rain down on the upper atmosphere. On Earth, these particles are guided toward the poles by the planet's global magnetic field. On Mars, though, there's no organized planetary magnetic field to guide the particles north and south, which means that they can go anywhere.

In the aurora that MAVEN witnessed, the solar particles penetrated deeply into the Martian atmosphere, sparking auroras less than 100 km from the surface, which is far lower than auroras on Earth. The researchers believe that to humans, the auroras would look like a diffuse green glow in the Martian sky.

Currently, the scientists are looking forward to future data to learn a bit more about this phenomenon.

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