A NASA image captured from the International Space Station taken on Sept 26, 2011 shows rare aurora appearing in red. The colours depend on which atoms are causing the splash of light seen in the aurora. In most cases, the light comes when a charged particle sweeps in from the solar wind and collides with an oxygen atom in Earth atmosphere. This produces a green photon, so most auroras appear green. However, lower-energy oxygen collisions as well as collisions with nitrogen atoms can produce red photons - so sometimes aurora also show a red band as seen here. [Photo/Agencies]