The Astronomical Journal – Early astronomers reported seeing canals on Mars and now a modern group has found a mysterious dark streak on Pluto, the most distant planet in the Solar System.

Pluto is covered with nitrogen frost, containing traces of carbon dioxide ice. The dark, reddish streak just south of its equator may indicate a region where more complex molecules exist.

Pluto is so far out that some astronomers no longer think it’s a planet. Images from Pluto are small and blurred and it’s hard to see details clearly, even using the Hubble Space Telescope.

Scientists will be able to find out more when we send a space probe past Pluto, but that won’t happen until 2015 at the earliest.

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