Dubbed "Christmas lights," the onslaught of electromagnetic activity lit up the Martian atmosphere for nearly a week in the run up to December 25. The aurora was detected by MAVEN's Imaging Ultraviolet Spectrograph (IUVS). The light show spread across Mars' northern hemisphere -- much as the Northern Lights do on Earth.
An aurora is a phenomenon whereby a mass of highly charged particles (mostly electrons and protons) collides with the atmosphere, causing the gas particles to glow. The ionization and excitation of different gases causes varied coloration.