| A plot of the 13,000 auroral events detected in the past six years by Mars Global Surveyor shows them clustering around the margins of the regions of strong surface magnetic field, mostly in the southern hemisphere. The margins are where the magnetic field lines converge on the surface, funneling electrons that crash into atmospheric carbon dioxide and generate the ultraviolet flashes. The red X marks the spot where Mars Express first detected an aurora last year. (Credit: David Brain & Jasper Halekas/SSL) |
