Swirling clouds of gas and dust rich in CO2, not water form planets, study finds

In the swirling clouds of gas and dust that surround newborn stars, planets begin to form. These planet-forming disks are rich with clues about how worlds like Earth come to be. Until now, scientists believed water vapor played a starring role in the early stages of planet creation. But a groundbreaking study from Stockholm University is rewriting that story.

Led by PhD student Jenny Frediani, the team uncovered a young disk with a shocking twist: it’s full of carbon dioxide (CO₂), not water. Using the James Webb Space Telescope (JWST), Frediani and her colleagues observed an unusually CO₂-rich disk in a region where Earth-like planets might form. This discovery challenges the long-standing belief that water dominates the inner parts of planet-forming regions.

“Unlike most nearby planet-forming disks, where water vapor dominates the inner regions, this disk is surprisingly rich in carbon dioxide,” says Frediani.

The results were published in the scientific journal Astronomy & Astrophysics. What makes this finding so important is how different it is from what scientists expected. Normally, in the warmer inner regions of a planet-forming disk, ice from the outer parts melts and turns into water vapor. This process usually leaves strong water signals in the data. But in this case, water is nearly undetectable.

“In fact, water is so scarce in this system that it’s barely detectable — a dramatic contrast to what we typically observe,” Frediani adds.

To understand why this is such a big deal, it helps to know how planets form. When a star is born from a cloud of gas, it pulls some of that material into a flat, spinning disk. This disk contains tiny dust grains and pebbles, some of which are covered in ice. As these pebbles drift toward the warmer parts of the disk, their ices turn into vapor. This vapor then becomes part of the gas that helps shape new planets.

In most disks, this process results in large amounts of water vapor near the star. But in the newly studied disk, located in the massive star-forming region NGC 6357, the team found something different. The carbon dioxide levels were much higher than expected, and water seemed to be missing.

“This challenges current models of disk chemistry and evolution since the high carbon dioxide levels relative to water cannot be easily explained by standard disk evolution processes,” says Frediani.

So, what might be causing this unusual chemistry? One possibility is radiation. The host star — or maybe nearby massive stars — could be sending out strong ultraviolet rays that change how the chemicals in the disk react. This kind of intense radiation could break apart water molecules or prevent them from forming in the first place, allowing CO₂ to dominate.

“Such a high abundance of carbon dioxide in the planet-forming zone is unexpected,” says researcher Arjan Bik, also from Stockholm University. “It points to the possibility that intense ultraviolet radiation — either from the host star or neighbouring massive stars — is reshaping the chemistry of the disk.”

Another fascinating part of this discovery involves isotopes. In addition to regular carbon dioxide, the team found isotopologues — forms of CO₂ that contain rare versions of carbon or oxygen. These versions include carbon-13 and oxygen-17 or oxygen-18.

These subtle chemical fingerprints could hold important clues. Similar isotopic signatures have been found in meteorites and comets from our own Solar System. Scientists have long puzzled over how these patterns formed. By studying them in faraway disks like this one, researchers hope to solve that mystery.

Isotopes act like a time machine, offering hints about the early stages of a planetary system. Because this CO₂-rich disk shows clear isotopic signals, it may help researchers piece together the story of our own solar neighborhood and how planets like Earth gained their unique chemistry.

The disk was found 1.7 kiloparsecs — or about 53 quadrillion kilometers — from Earth. That’s roughly 5,300 times farther than Pluto. This massive distance didn’t stop the team from gathering highly detailed observations, thanks to the power of JWST.

All of this was made possible by the James Webb Space Telescope. More specifically, the team used JWST’s MIRI instrument — short for Mid-Infrared Instrument. MIRI is a special tool that allows scientists to see through thick dust that blocks other telescopes. It collects light in the infrared part of the spectrum, which is perfect for studying cold, dusty objects like planet-forming disks.

MIRI works like both a camera and a spectrograph. It can not only take images but also break light into its parts to identify what chemicals are present. It operates between 5 and 28 microns — ideal for detecting gases like CO₂ and water vapor. It also has a special tool called a coronagraph, which helps block starlight to spot smaller objects nearby, such as exoplanets.

Astronomers from Stockholm University and Chalmers University helped develop this powerful instrument. Now, it’s giving them a better look at how planets form under extreme conditions.

Thanks to MIRI, scientists can now compare disks from different environments — both quiet and chaotic. By doing this, they’re starting to understand just how much a planet’s birthplace affects its future. Conditions in a planet-forming disk could determine whether that planet ends up dry like Mars or water-rich like Earth.

Maria-Claudia Ramirez-Tannus, a scientist at the Max Planck Institute for Astronomy in Heidelberg and lead of the XUE (eXtreme Ultraviolet Environments) collaboration, highlights why this matters.

“It reveals how extreme radiation environments — common in massive star-forming regions — can alter the building blocks of planets,” she explains. “Since most stars and likely most planets form in such regions, understanding these effects is essential for grasping the diversity of planetary atmospheres and their habitability potential.”

This research is part of the XUE project, which focuses on how ultraviolet radiation affects the chemistry of planet-forming disks. These environments are far more intense than the calm region where our Solar System likely formed.

This discovery is more than just a surprise. It’s a signal that scientists may need to rethink how planetary systems take shape. If high carbon dioxide levels can form naturally under certain conditions, it could mean that planets with CO₂-heavy atmospheres are more common than previously thought.

That, in turn, affects how we search for life beyond Earth. Planets with very different starting ingredients may develop unique atmospheres, weather patterns, and surface conditions. Some of them may be too harsh to support life, while others might just surprise us.

At the same time, the data could help solve old questions about Earth and its neighbors. Why does Earth have so much water, while Venus and Mars do not? Could radiation have stripped away their water early on? Or did they form from disks with different chemistry altogether?

The new findings offer a fresh path forward. With better tools and sharper data, researchers can dig deeper into how planets form and what makes them habitable.

The road ahead includes more observations of disks in both calm and harsh environments. As researchers gather more data, they’ll be able to build better models and update the theories that guide planet science today.

Stockholm University’s work is just the beginning. The James Webb Space Telescope will continue to open new windows into the universe — and into our own origins.

Note: The article above provided above by The Brighter Side of News.

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