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Large amounts of methane in Pluto's atmosphere observed
Updated: 2009-03-04 21:21

PARIS -- Using the Very Large Telescope of the European Organization for Astronomical Research in the Southern Hemisphere (ESO), astronomers have found unexpectedly large amounts of methane in Pluto's atmosphere, gaining new insight into the dwarf planet.

The scientists also found that Pluto's atmosphere is hotter than the surface by about 40 degrees Celsius, although it still only reaches a frigid minus 180 degrees Celsius, ESO reported Tuesday.

"With lots of methane in the atmosphere, it becomes clear why Pluto's atmosphere is so warm," says lead researcher Emmanuel Lellouch.

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Pluto, which is about a fifth the size of the Earth, is composed primarily of rock and ice. As it is about 40 times further from the Sun than the Earth on average, it is a very cold world with a surface temperature of about minus 220 degrees Celsius.

Until recently, only the upper parts of the atmosphere of Pluto could be studied, which is some 50 degrees Celsius warmer than the surface. The new observations made by a unique equipment attached to ESO's Very Large Telescope have now revealed that the atmosphere as a whole, not just the upper atmosphere, has a mean temperature of minus 180 degrees Celsius, and so it is indeed "much hotter" than the surface.

"It is fascinating to think that with the equipment, we are able to precisely measure traces of gas in an atmosphere 100,000 times more tenuous than the Earth's, on an object five times smaller than our planet and located at the edge of the Solar System," said co-researcher Hans-Ulrich Kaufl.