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<b>Distant planetoid Sedna gives up more secrets</b><br />10:51 15 April 2005 <br />NewScientist.com news service <br />Maggie McKee <br /><br />The distant planetoid Sedna appears to be covered in a tar-like sludge that gives it a distinctly red hue, a new study reveals. The findings suggests the dark crust was baked-on by the Sun and has been untouched by other objects for millions of years.<br /><br />Sedna appears to be nearly the size of Pluto and was discovered in November 2003. It is the most distant object ever seen within the solar system and travels on an elongated path that stretches from 74 to 900 times the distance between the Sun and the Earth. <br /><br />Astronomers have struggled to explain such an extreme orbit, but many believe a star passing by the Sun about 4 billion years ago yanked the planetoid off its original, circular course.<br /><br />Now, observations by the same team that discovered Sedna suggest the object has since led an uneventful life. Infrared spectra taken with the Gemini Observatory in Hawaii show the surface of the planetoid contains little methane ice, found in significant amounts on Pluto, and little water ice, seen on Pluto’s moon, Charon.<br /><br />Hydrocarbon sludge<br />Chad Trujillo, the team's lead researcher at the Gemini Observatory, says collisions with other objects may have helped expose the icy interiors of Pluto and Charon and believes a lack of collisions might explain Sedna's ice-free surface. <br /><br />He says Sedna, which is probably made up of an equal mixture of ice and rock, may be covered with a metre or so of hydrocarbon sludge. This sludge is produced when the Sun's ultraviolet radiation and charged particles alter the chemical bonds between atoms in the ice.<br /><br />"You just get this big tangle of carbon and hydrogen bonds, which turns the surface dark like asphalt or tar," he told New Scientist. A similar "space weathering" process occurs on a 200-kilometre-wide object called Pholus, which lies near Saturn and <div class="Discussion_UserSignature"> <font color="#800080">"All God does is watch us and kill us when we get boring. We must never, ever be boring" - <strong>Chuck Palahniuk</strong>.</font> </div>