NASA's Cassini spacecraft flew within 1000 kilometres of the moon on 10 September, it saw much some complicated patterns on the surface of the moon Iapetus. Previous to this flyby, Iapetus was thought to have the strange feature of one bright side and one dark side. Not just from lighting, but composed of different materials on each side. Now the Cassini probe shows that the strange features are even more complex. Iapetus has a landscape unlike anything else in the solar system: sharp-edged islands of dark material within pale regions, and patches of white ice on the dark mountainsides. The coating of dark material is a puzzle. "We think it's thin, probably no more than a few metres, because we see an impact that's not very big but has punched through to show the bright material beneath," says Carolyn Porco. ( head of the Cassini imaging team at the Space Science Institute in Boulder, Colorado, US.) "But that's about all we know right now." She suspects that the dark stuff was swept up from space by the leading hemisphere of Iapetus. "Where that material came from is still a mystery," Porco told New Scientist. "Maybe from a moon further out, maybe a pre-existing body that got disrupted?"Thanks to Shaun A. Saunders for the post
(Image: NASA/JPL/Space Science Institute)
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