Mars, Hubble Space Telescope image. North is at top. A large dust storm is seen at centre (brighter orange area). Mars was 43 million kilometres from Earth during this close approach on 28 October 2005. This is the Martian summer in the southern hemisphere, and the southern polar ice cap has largely sublimated. The blueish-white areas at top and at left are water-ice clouds. Mars, the fourth planet from the Sun, has a diameter of around 6800 kilometres. This image was obtained with Hubble's Advanced Camera for Surveys instrument.