Planetary scientists have long thought that Pluto would have a surface temperature of about -279º Fahrenheit, but the New Horizons flyby in 2015 revealed a much colder dwarf planet with a surface temperature closer to -333º Fahrenheit.
While the results stumped researchers at first, the results revealed a haze in Pluto's atmosphere that might be to blame for these unexpectedly-low temperatures. It appears to be made up of nitrogen and methane, which ionize when struck by sunlight. When this happens, their molecules combine to form hydrocarbons and drop to the dwarf planet's surface.
These particles' impressive thermal cooling rates, combined with their abundance in Pluto's atmosphere, helps to reduce Pluto's heat overall. Furthermore, scientists wonder whether a similar (albeit human-made) process could reverse the effects of global warming here on Earth.