Spaceflightnow is reporting that Martian Aurora are far more common than previously thought:

The discovery of hundreds of auroras over the past six years comes as a surprise, since Mars does not have the global magnetic field that on Earth is the source of the aurora borealis and the antipodal aurora australis.

According to the physicists, the auroras on Mars aren't due to a planet-wide magnetic field, but instead are associated with patches of strong magnetic field in the crust, primarily in the southern hemisphere. And they probably aren't as colorful either, the researchers say: The energetic electrons that interact with molecules in the atmosphere to produce the glow probably generate only ultraviolet light - not the reds, greens and blues of Earth.

~ I was cruising 'round on Mars one day... ~