Plutos lower atmosphere revealed by scientists

March 3rd, 2009 - 2:04 pm ICT by ANI  

Munich, March 3 (ANI): Astronomers have used the European Southern Observatorys (ESOs) Very Large Telescope (VLT) to gain valuable new insights about the lower atmosphere of the dwarf planet Pluto.

The scientists found unexpectedly large amounts of methane in the atmosphere, and also discovered that the atmosphere is hotter than the surface by about 40 degrees, although it still only reaches a frigid minus 180 degrees Celsius.

These properties of Plutos atmosphere may be due to the presence of pure methane patches or of a methane-rich layer covering the dwarf planets surface.

With lots of methane in the atmosphere, it becomes clear why Plutos atmosphere is so warm, said Emmanuel Lellouch, lead author of the paper reporting the results.

Pluto, which is about a fifth the size of 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.

It has been known since the 1980s that Pluto also has a tenuous atmosphere, which consists of a thin envelope of mostly nitrogen, with traces of methane and probably carbon monoxide.

As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground.

In periods when it is closer to the Sun - as it is now - the temperature of Plutos solid surface increases, causing the ice to sublimate into gas.

Until recently, only the upper parts of the atmosphere of Pluto could be studied.

By observing stellar occultations, a phenomenon that occurs when a Solar System body blocks the light from a background star, astronomers were able to demonstrate that Plutos upper atmosphere was some 50 degrees warmer than the surface, or minus 170 degrees Celsius.

These observations couldnt shed any light on the atmospheric temperature and pressure near Plutos surface.

But unique, new observations made with the CRyogenic InfraRed Echelle Spectrograph
(CRIRES), attached to ESOs 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.

In contrast to the Earths atmosphere, most, if not all, of Plutos atmosphere is thus undergoing a temperature inversion: the temperature is higher, the higher in the atmosphere you look. (ANI)

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