After almost 20 years of hunting for telltale clues, we now know that the demoted planet Pluto has an atmosphere of small but still very deadly amounts of carbon monoxide gas which helps keep it at incredibly cold temperatures.
British researchers have found that Pluto's atmosphere is much, much larger than originally suspected. While initial estimates put the dwarf planet's atmosphere at up to 100km above the surface, these new results actually indicate it has an atmosphere that's some 3000km high, or about a quarter of the distance between Pluto and its main moon Charon.
The carbon monoxide in Pluto's atmosphere is extremely cold, averaging around 220C. Its temperatures fluctuate along with that of methane, the only other confirmed gas in Pluto's atmosphere. (Both of these are still only present in trace quantities - researcher believe nitrogen is the main component of Pluto's atmosphere, but that remains unconfirmed.)
The carbon monoxide likely interacts with the methane to keep Pluto's temperature relatively stable:
In Pluto's atmosphere, carbon monoxide acts as a coolant, while methane absorbs sunlight, which produces heating. Maintaining a balance between the two gases, which are actually just trace elements in what is thought to be an atmosphere dominated by nitrogen, is critical during the long seasons on Pluto that last several decades.
The newly discovered carbon monoxide could play a key role in slowing the loss of Pluto's atmosphere. But, if the chilling effect is too great, it could result in nitrogen snowfalls and all the gases freezing on the ground, the researchers said.
Lead researcher Jane Greaves says Pluto could also be useful as a test case for Earth's atmosphere:
"Seeing such an example of extraterrestrial climate change is fascinating. This cold simple atmosphere that is strongly driven by the heat from the sun could give us important clues to how some of the basic physics works, and act as a contrasting test-bed to help us better understand the Earth's atmosphere."