Pluto’s high-altitude haze challenges climate norms

Pluto is once again challenging human understanding of planetary climates. 

New data from the James Webb Space Telescope (JWST) reveal that Pluto’s high-altitude haze plays a vital role in shaping the dwarf planet’s climate, offering fresh clues about Earth’s early atmosphere, Caliber.Az reports via LiveScience.

When NASA’s New Horizons spacecraft flew past Pluto in 2015, it overturned the image of the dwarf planet as a barren ice ball, revealing vast icy plains, jagged mountains, and a striking bluish, multi-layered haze stretching more than 185 miles (300 kilometers) above its surface—far higher and more complex than scientists expected.

Nearly a decade later, JWST observations confirm that this haze is not just a visual feature but a key climate driver. “This is unique in the solar system,” said Tanguy Bertrand, an astronomer at the Paris Observatory and lead author of the new study published June 2 in Nature Astronomy. “It's a new kind of climate, let's say.”

The haze is composed of complex organic molecules formed by sunlight-driven reactions between methane and nitrogen. Models proposed in 2017 suggested these particles absorb sunlight during the day and release infrared radiation at night, cooling Pluto’s atmosphere more effectively than gases alone. This could explain why Pluto’s upper atmosphere is about -333°F (-203°C), some 30 degrees cooler than expected.

Confirming this was difficult because Pluto’s moon, Charon, orbits so closely that their thermal signals often overlap. “Basically, we couldn’t know what part of the signal is due to Charon and what part is due to Pluto’s haze,” Bertrand said.

JWST’s infrared instruments finally separated these signals in 2022, revealing the faint infrared glow of Pluto’s haze matched predictions. “In planetary science, it's not common to have a hypothesis confirmed so quickly,” said Xi Zhang, lead author of the 2017 study.

The findings suggest similar haze-driven climates may exist on other moons like Neptune’s Triton and Saturn’s Titan. They also offer insights into Earth’s early atmosphere, which may have been cloaked in a protective organic haze fostering stable temperatures and life’s emergence. “By studying Pluto's haze and chemistry, we might get new insights into the conditions that made early Earth habitable,” Zhang noted.

By Naila Huseynova