Atmospheric halos or arcs of light in the sky as pictured - are caused by the play of sunlight on ice crystals in the atmosphere. Now, where I come from in Queensland Australia, this is something that I have never seen before. We have rainbows, which as we know, is sunlight playing on water droplets. So one could say that the halos here are Antarcticas version of the rainbow. These halos of course are not just confined to the polar regions. Anywhere that the atmospheric temperatures are low and ice crystals form, there is a chance of a halo been seen. The most common halos are those formed by flat hexagonal crystals known as plate crystals.These crystals are only around 0.2mm across. The large arc is known as a circumzenith arc. This halo was taken at Australian Antarctic Station, Casey 31 March 2011.