Mars. Mars Global Surveyor image of Mars during the summer in the northern hemisphere. This means it is winter in the southern hemisphere, and the south polar ice cap (white, bottom) is at its largest. The large dark feature at centre is Syrtis Major, a volcanic plain. At lower centre, just above the ice cap, is the bright Hellas Basin. This is a huge impact basin around 2200 kilometres in diameter. This image was taken by the Mars Orbiter Camera (MOC) on the MGS spacecraft in orbit around Mars.