Blame Pluto’s haze for the dwarf planet’s unexpected chilliness. Clusters of hydrocarbons in the atmosphere radiate heat back into space, keeping the dwarf planet cool, a new study suggests. Pluto may be the only world in the solar system whose atmospheric temperature is controlled by solid particles, rather than gas, researchers report in the Nov. 16 Nature.
Most planets’ temperatures are set by the gas content of their atmospheres, since certain gases trap heat from the sun more efficiently than others (SN Online: 6/8/15). Based on the nitrogen, methane and carbon monoxide in Pluto’s atmosphere, scientists predicted the dwarf planet’s upper atmosphere would be a brisk –173° Celsius.