At a distance from the Sun around 40 times farther than the Earth, the dwarf planet Pluto is certainly cold. However, its atmospheric temperature of 70 K is 30 K lower than it theoretically should be. Now, a team at the University of California, Santa Cruz has offered an explanation for the mismatch.
The temperature of a planetary atmosphere is generally dictated by its atmospheric gas composition, which determines the proportion of incident solar energy retention. However, on Pluto, sooty aggregate particles of small hydrocarbons have a previously unconsidered shielding effect. Energy is absorbed, then re-emitted into space. “Pluto is the first planetary body we know of where the atmospheric energy budget is dominated by solid-phase particles,” said lead author Xi Zhang.
As the soot should cause a small change in the infrared emissions of the dwarf planet, the theory, published in Nature, may be confirmed after the 2019 launch of the James Webb Space Telescope (JWST). For more information on the JWST, see “Into the Unknown” in this issue of The KAIST Herald.