New James Webb Space Telescope data reveal Pluto's high-altitude haze is a key driver of the climate on the dwarf planet, offering clues to Earth's ancient atmosphere.
Astronomers using the James Webb Space Telescope (JWST) have
taken a fresh look at the distant edges of our solar system — and found that,
once again, Pluto is defying expectations.
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Pluto's mysterious blue haze is the primary driver of the
dwarf planet's climate. (Image credit: NASA/JHUAPL/SwRI) |
When NASA's New Horizons spacecraft flew past Pluto in 2015,
it shattered the notion that the dwarf planet was a dormant ball of ice,
instead revealing it to be rich with icy plains and jagged mountains. But one
of the biggest surprises floated above it all: a bluish, multi-layered haze
blanketing the world's sky, stretching more than 185 miles (300 kilometers)
above the surface — far higher and more intricate than scientists had
predicted.
Now, nearly a decade later, new data from JWST confirm that
Pluto's haze isn't just a visual oddity, it also controls the dwarf planet's
climate.
"This is unique in the solar system," Tanguy
Bertrand, an astronomer at the Paris Observatory in France who led the
analysis, told. "It's a new kind of climate, let's say."
The findings, described in a study published June 2 in the
journal Nature Astronomy, suggest similar dynamics may be at play on other
haze-shrouded worlds in our solar system, and even offer clues about our own
planet's early climate.
Lifting the haze
Pluto's high-altitude haze is made of complex organic
molecules from sunlight-driven reactions of methane and nitrogen. The idea that
this haze could control Pluto's climate was first proposed in 2017. Computer
models suggested these particles absorb sunlight during the day and release it
back into space as infrared energy at night, cooling the atmosphere much more
efficiently than gases alone. This could also explain why Pluto's upper
atmosphere is roughly -333 degrees Fahrenheit (-203 degrees Celsius) — 30
degrees cooler than expected.
For years, however, testing that theory proved difficult.
One major challenge was Pluto's large moon, Charon, which orbits the frigid
planet so closely that their thermal signals often overlap in telescope data.
"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.
The researchers behind the 2017 study predicted that Pluto's
haze would make the world unusually bright in mid-infrared wavelengths — a
prediction that, at the time, could only be tested with future instruments.
That opportunity arrived in 2022, when JWST's powerful infrared instruments
were finally able to separate the two worlds' signals. Sure enough, the faint
infrared glow of Pluto's haze matched the predictions.
"In planetary science, it's not common to have a
hypothesis confirmed so quickly, within just a few years," Xi Zhang, a
planetary scientist at the University of California, Santa Cruz who led the
2017 team, said in a statement. "So we feel pretty lucky and very
excited."
These findings also open up the possibility that similar
haze-driven climates might exist on other hazy worlds, such as Neptune's moon
Triton or Saturn's moon Titan, Bertrand said.
Even Earth's distant past might bear a resemblance, the
researchers said. Before oxygen transformed our planet's skies, it's possible
that Earth was veiled in a haze of organic particles — a blanket that may have
helped stabilize temperatures and foster early life.
"By studying Pluto's haze and chemistry, we might get
new insights into the conditions that made early Earth habitable," Zhang
said in the statement.
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