For more than 10 years, scientists have been deciphering the mysterious atmosphere of the famous “Pink Planet.” Now, thanks to observations from the James Webb Space Telescope (JWST), astronomers have discovered that the object harbors unusual salty clouds and exotic chemistry in its atmosphere. The findings were recently published in The astronomical magazineand provide the first direct evidence of salt clouds in the atmosphere of a cold object.

Discovered in 2013, GJ504b orbits a Sun-like star 57 light years from Earth. Despite its nickname, scientists aren’t really sure if it is a planet. GJ504b has a mass about 25 times that of Jupiter and may in fact be a brown dwarf, a failed star that straddles the line between planet and star. That’s why astronomers refer to it as a “planetary-mass companion,” meaning it’s a planet-sized object orbiting a star.

GJ504b has a temperature of only 550 degrees Fahrenheit, making it difficult to study from Earth. “The Pink Planet is the coldest companion ever discovered using ground-based instruments,” Aneesh Baburaj, co-author of the study and an astronomer at Northwestern University, said in a statement.

“Many teams around the world made follow-up observations to study its light, but it was too weak for ground-based instruments,” he added. “That made it a perfect target for JWST. When we finally got its spectrum, it immediately looked interesting. But once we started digging into the data, we realized it was unlike anything we’d ever looked at before.”

JWST captured the faint light of GJ504b, and researchers used advanced data processing techniques to filter out the glow from its bright host star. Filtering allowed them to break down the light from GJ504b into component colors, each of which represents a different element present in its atmosphere.

“In the past, other astronomers observed its companion for an entire night with some of the largest telescopes in the world to obtain a spectrum,” Baburaj said. “And they couldn’t see the object. With JWST, our entire observation lasted about two hours and we were successful.”

The team discovered that the Pink Planet’s atmosphere houses water vapor, methane, carbon dioxide, ammonia and other molecules. But something was still missing from the equation. When they fed the data into a computer model to reconstruct the companion star, the simulated atmosphere would only match their observations if it contained unusual and implausible features.

Once they added clouds to their simulation, it became clear that only salty clouds could explain what they were seeing.

“We tested three different types of clouds, and salt clouds were the best fit. When we took salt clouds into account, they attenuated the signature of molecules hidden deeper in their companion’s atmosphere. Then the results became physically possible,” Baburaj explained.

Scientists still have more to learn about GJ504b, including how the mysterious object formed in the first place. But the authors of this study believe that the findings could serve as a basis for research on other cold, faint planets.

“This is the first time we have discovered that salt clouds are instrumental in explaining the spectrum of an object,” Baburaj added. “It’s a good reminder to take clouds into account in our models.”

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