Excerpt from engadget.com
As much as humanity knows about Mars, the planet is still chock-full of surprises. Just ask NASA: University of Colorado researchers using its MAVEN probe have discovered phenomena in the Martian skies that you would never see on Earth. For one, there are auroras that are so energetic (their electrons are 100 times more powerful than a spark of house current) that they plunge far deeper into the atmosphere than back home, or even other places on Mars. Scientists suspect that the Sun is to blame -- Mars doesn't have a protective magnetic field like Earth does, so the solar wind sometimes hits with full force.
Another discovery may be tougher to crack. MAVEN has spotted very thin dust clouds flying at very high altitudes of 93 to 190 miles, where they shouldn't exist based on the current understanding of how Mars works. The clouds could simply have been kicked up from the ground, but they could also come from Mars' moons or even comet debris. Whatever the causes, both the dust and the auroras suggest that there's still a lot to learn about one of Earth's closest cosmic neighbors.