Webb Finds Salt Clouds Floating Over the 'Pink Planet'

Picture a world where the clouds drifting through the sky aren't made of water or dust, but of salt. That is exactly what the James Webb Space Telescope has now found hanging in the atmosphere of a distant, faintly glowing world astronomers nicknamed the Pink Planet. After years of being unable to make sense of the light from this object, researchers finally cracked it by realising its skies are veiled in salty cloud.

The discovery, announced in June 2026 and published in The Astronomical Journal, gives some of the first direct evidence that salt clouds can form in the atmosphere of a cold world far from Earth. It's a phenomenon scientists had only theorised about for more than 15 years. Now there's a real object that fits the picture.

A salty sky 57 light-years away

The world in question is GJ 504b, which sits about 57 light-years from Earth, circling a Sun-like star in the constellation Virgo. It was first spotted in 2013 through direct imaging by Japan's Subaru Telescope in Hawaii, and it became famous almost immediately for its colour. Instead of the deep red glow of a young, hot giant, GJ 504b shines a dull magenta, a shade often compared to dark cherry blossom. Hence the nickname.

What Webb added was the chemistry of its air. When researchers fed Webb's data into their atmospheric models, nothing matched. The light coming back simply refused to line up with the usual recipes of gas and haze. The breakthrough came when they added salt clouds to the calculation. Suddenly the numbers fit.

Those clouds appear to be smothering the deeper, hotter layers of the atmosphere, acting like a veil that changes which wavelengths of light escape into space. Account for that veil, and the once-baffling spectrum becomes readable.

Why salt, of all things

It sounds strange that something as ordinary as salt could be drifting through an alien sky, but it makes sense once you think about temperature. GJ 504b is hot by human standards, sitting around 550 degrees Fahrenheit (290°C). Yet for a giant gas world, that's astonishingly cold. It's one of the coolest companions ever directly imaged from the ground.

At those temperatures, certain compounds that would normally stay as vapour can condense into solid or liquid droplets and form clouds, much as water does on Earth. Salts are among the substances long predicted to do exactly this in cool atmospheres. The theory had been around for well over a decade. What was missing was a clear, real-world example.

Lead researcher Aneesh Baburaj, a postdoctoral associate at Northwestern University's CIERA astrophysics centre, summed up the significance simply: this is the first time salt clouds have proven critical to explaining the spectrum of an object. In other words, you cannot understand this world without them.

Two hours that beat years of effort

One of the most striking parts of the story is how quickly Webb solved a problem that had frustrated astronomers for years. Multiple teams had tried to study GJ 504b from the ground, but the object is faint and sits dangerously close to the glare of its bright host star. Collecting enough clean light to read its atmosphere was painfully hard.

Webb changed the equation. Using its sensitivity in infrared light, plus careful data processing to strip away the star's overwhelming glow, the team captured a full spectrum in roughly two hours. Years of struggle on the ground, answered in an afternoon of telescope time in space.

That efficiency matters far beyond this one world. Cold, faint, far-flung objects like GJ 504b have always been some of the hardest targets in astronomy. Showing that Webb can characterise one so cleanly opens the door to studying many more.

More than just salt in the air

The salt clouds were the headline, but they weren't the only thing Webb detected. The spectrum revealed a rich cocktail of chemistry, including:

• Water vapour
• Methane
• Carbon dioxide
• Ammonia
• An unusually high abundance of heavy elements, what astronomers call metals

That last point is the intriguing one. GJ 504b appears to be packed with far more heavy elements than expected. That enrichment is a clue to how it was born, and it deepens an old debate about what this object really is.

Planet, or failed star?

GJ 504b has always been an awkward case to classify. When it was discovered in 2013, early estimates pegged it at around four times the mass of Jupiter, assuming the system was young. But later work suggested the star is far older, somewhere between 2.5 and 4 billion years. Age matters here, because an older object of the same brightness must be heavier to still glow as it does.

Under the older-age scenario, GJ 504b's mass balloons to roughly 25 times Jupiter's mass. That pushes it out of comfortable planet territory and toward the fuzzy boundary of a brown dwarf, the class of objects too big to be planets but too small to ignite as true stars. Its heavy-element load only muddies the question further, since it could hint at either a planet-like formation in a disk of debris or a more star-like origin.

For now, scientists are honest about the uncertainty. GJ 504b sits right on the dividing line, and the salt clouds don't settle the argument. What they do is give researchers a far better handle on the atmosphere itself, which is the first step toward eventually answering the bigger question.

Why this discovery travels

There's a reason this story is worth sending to a friend. It collapses something exotic, an alien sky, into something instantly relatable: salt, the same stuff sitting on your kitchen table, forming clouds on a magenta world dozens of light-years away. The image practically writes itself.

But underneath the wow factor is a genuine scientific lesson. Clouds are the great spoilers of exoplanet science. They hide the layers below and warp the light we use to read distant atmospheres. By proving that salt clouds are not just a theory but a real, measurable feature, this work reminds astronomers to build clouds into their models from the start, rather than treating them as an afterthought.

GJ 504b spent years as a beautiful puzzle no one could quite solve. A few hours of Webb's attention, and the Pink Planet finally gave up one of its secrets. The fact that the answer turned out to be salt is the kind of detail that makes the universe feel both stranger and oddly familiar at the same time.