JWST Reveals Pluto’s Haze Cools Atmosphere, Paints Charon’s Poles Red

JWST confirms Pluto’s haze cools its mesosphere and drives methane escape, coating Charon’s poles red. The haze absorbs UV light, heats the upper atmosphere, and re-radiates heat as infrared.

Written by Gadgets 360 Staff | Updated: 15 June 2025 15:32 IST

JWST Reveals Pluto’s Haze Cools Atmosphere, Paints Charon’s Poles Red

Photo Credit: NASA

Pluto’s haze cools its skies and drifts to Charon, painting its poles a mysterious red

Highlights

Pluto’s haze layer cools its mesosphere by radiating heat into space
Methane escape from Pluto stains Charon’s poles red with tholins
JWST confirms haze balances Pluto’s energy and drives molecule escape

Pluto and its moon Charon are shown with a thin haze of organic particles covering Pluto's sunlit side. The haze both cools Pluto's upper atmosphere by radiating heat into space and absorbs ultraviolet light that helps propel methane molecules to escape. This explains why Pluto's mesosphere is colder than expected and why methane is leaking and even coating Charon's poles red. The effect was predicted by Xi Zhang, and new JWST/MIRI observations confirm it. The results have implications for understanding Titan's haze and Earth's early atmosphere.

A Haze that Cools and Warms Pluto

According to a new study, using JWST's mid-infrared observations, a team led by Tanguy Bertrand detected thermal emission from this haze layer. The tiny aerosol particles are thought to be complex hydrocarbons (“tholins”) and ices. These particles absorb the Sun's ultraviolet light, heating the upper atmosphere and giving methane molecules extra energy. The haze then re-radiates that energy as infrared light, cooling the middle layers.

In fact, Zhang's models show Pluto's gases alone would overheat the mesosphere, so the haze must supply net cooling to balance the energy budget. Together, these effects mean the haze largely controls Pluto's atmospheric energy balance. How much net warming versus cooling occurs depends on particle size and composition.

ESA’s Solar Orbiter Unveils First View of the Sun’s Mysterious South Pole

Haze Drives Escape and Paints Charon Red

Pluto's atmosphere is so thin that any nudge can send molecules into space. Planetary scientist Will Grundy estimated Pluto loses about 1.3 kg/s of methane, with roughly 2.5% intercepted by Charon. The haze layer provides that nudge: its particles absorb solar UV light, heating molecules until they can escape Pluto's gravity. The escaping methane then deposits on Charon's poles, where radiation transforms it into complex, reddish tholin compounds.

This process effectively lets Pluto “paint” Charon's poles with organic red stain—a phenomenon not seen elsewhere in the Solar System. By linking Pluto's climate and Charon's surface chemistry, the haze-driven escape provides a rare example of atmospheric exchange on icy worlds.

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