Just when I thought the Rosetta mission couldn't surprise me any more, it does exactly that. Using multiple instruments on board the spacecraft, scientists found that the comet 67P/Churyumov-Gerasimenko has a glowing aurora! Faint, but it's there, and it's definitely what I would classify as an actual aurora.
That's bizarre, and cool.
An aurora on Earth is a glow in the sky caused by subatomic particles streaming away from the Sun. The Earth has a magnetic field, like a giant bar magnet, and that accelerates the electrons in the solar wind as they approach the Earth. It funnels them to the north and south magnetic poles (which are relatively close to the physical poles) where they slam into our atmosphere. They hit the oxygen and nitrogen and give those electrons energy, sometimes even knocking them right off the atoms and molecules. When the electrons release that energy (or recombine with the atoms), they emit light at a specific wavelength — color. What we see down on the ground is a beautiful and eerie sheet of color; green, red, even pink, and blue, depending on the kind of atom or molecule.
This is why I was surprised at the news about ...