Astronomy Picture of the Day

Explanation: What are these surface features on Titan? This planet-sized moon of Saturn had much of its south polar surface imaged during an initial flyby by the Saturn-orbiting Cassini spacecraft back in early July. The above image mosaic was digitally stitched together from pictures taken at a very specific colour of polarized infrared light, a colour not absorbed and little scattered by Titan's methane haze. Visible are light and dark regions that are not yet understood. Surface features as small as 10 kilometres are resolved from about 340,000 kilometres away. The white region near Titan's South Pole, left of centre, is unusually thick clouds also thought to be composed of methane. Today Cassini will swoop to within 1,500 kilometres above Titan and may return data and images that help humanity better understand this strange world.