Dramatic plumes, both large and small, spray water ice out from many locations along the famed tiger stripes near the south pole of Saturn’s moon Enceladus in this image released on Feb. 23, 2010. A study published in October 2025 analyzed data from NASA’s Cassini mission and found evidence of previously undetected organic compounds in a plume of ice particles like the ones seen here. The ice particles were ejected from the ocean that lies under Enceladus’ frozen shell. Researchers spotted not only molecules they’ve found before but also new ones that lay a potential path to chemical or biochemical activity.
Our exploration of the outer Solar System has revealed a host of icy moons, many with surface features that suggest a complex geology. In some cases, these features—most notably the geysers of Enceladus—hint at the presence of oceans beneath the icy surfaces. These oceans have been ascribed to gravitational interactions that cause flexing and friction within the moon, creating enough heat to melt the body’s interior.
Something that has received a bit less attention is that some of these orbital interactions are temporary or cyclical. The orbits of any body are not always regular and often have long-term cycles. That’s also true for the other moons that provide the gravitational stress. As a result, the internal oceans may actually come and go, as the interiors of the moons melt and refreeze.
A new study, released today by Nature Astronomy, looks at one of the consequences of the difference in density between liquid water and ice (about 10 percent): the potential for the moon’s interior to shrink as it melts, leaving an area of low pressure immediately below its icy shell. If the moon is small enough, this study suggests, that could cause the surface of the ocean to boil.
In this image captured by NASA’s Cassini spacecraft in 2009, dramatic plumes of water ice and vapor are seen erupting from the south pole of Saturn’s moon Enceladus.
NASA/JPL/Space Science Institute
Researchers dove deep into information gathered from the ice grains that were collected during a close and super-fast flyby through a plume of Saturn’s icy moon.
A new analysis of data from NASA’s Cassini mission found evidence of previously undetected organic compounds in a plume of ice particles ejected from the ocean that lies under the frozen shell of Saturn’s moon Enceladus. Researchers spotted not only molecules they’ve found before but also new ones that lay a potential path to chemical or biochemical activity.
The ice grains studied were collected just 13 miles (21 kilometers) from the moon’s surface and mark the first time scientists have observed this diversity of organics in fresh particles ejected from the subsurface water of Enceladus. Published Wednesday in Nature Astronomy, the findings signal an important step toward confirming active organic chemistry below the moon’s surface. This is the kind of chemical activity that could support compounds that are important to biological processes and are an essential component of life on Earth.
Besides increasing the diversity of detected organics, the recent work added a new layer to earlier findings by analyzing particles that the Cassini spacecraft collected when it flew directly through a plume — the next-best thing to diving directly into the moon’s ocean.
“Previously, we detected organics in ice grains that were years old and potentially altered by the intense radiation environment surrounding them,” said Nozair Khawaja of the Freie Universität Berlin, lead author of the study. “These new organic compounds were just minutes old, found in ice that was fresh from the ocean below Enceladus’ surface.”
Scientists knew from previous Cassini data-mining that nitrogen- and oxygen-bearing organic compounds were present in particles from Saturn’s E ring, a faint, wide outer band around the planet fed by the icy material that fans out from Enceladus’ plumes. But the new research analyzed ice grains from a moon plume itself — in other words, grains found closest to their subsurface origin.
“These molecules we found in the freshly ejected material prove that the complex organic molecules Cassini detected in Saturn’s E ring are not just a product of long exposure to space, but are readily available in Enceladus’ ocean,” said coauthor Frank Postberg, also of Freie Universität Berlin.
Fast and fruitful
The data was collected and sent to Earth in 2008, when ice particles impacted Cassini’s Cosmic Dust Analyzer instrument. Besides being directly sourced from a plume, the ice grains had another thing going for them: They’d been smashed to smithereens as they struck the instrument during the spacecraft’s fast fly-through at 11 miles per second (about 18 kilometers per second relative to the moon).
The energy of the impact vaporized the ice grains and ionized a substantial fraction of them. Those ions were then analyzed by the instrument’s mass spectrometer, which examined their chemical makeup.
The study’s authors were able to analyze the tiniest of fragments — smaller than a thousandth of a millimeter, smaller even than a flu virus — and identify organic compounds they hadn’t seen before in plume particles.
The newly detected compounds included those from the aliphatic and cyclic ester and ether families, some with double bonds in their molecular structures. Together with the confirmed aromatic, nitrogen- and oxygen-bearing compounds, these compounds can form the building blocks to support chemical reactions and processes that could have led to more complex organic chemistry — the kind that is of interest to astrobiology and narrows the focus of where we search for life in the solar system.
After flying through the plume, the spacecraft, managed by NASA’s Jet Propulsion Laboratory in Southern California, explored the complex Saturn system for nearly another decade.
More about Cassini
The Cassini-Huygens mission was a cooperative project of NASA, ESA (European Space Agency), and the Italian Space Agency. A division of Caltech in Pasadena, JPL managed the mission for NASA’s Space Mission Directorate in Washington and designed, developed, and assembled the Cassini orbiter.
NASA’s Webb Telescope Studies Moon-Forming Disk Around Massive Planet
An artistic rendering of a dust and gas disk encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Full image, annotation, and caption shown below.
Credits: Illustration: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zürich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)
NASA’s James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disk encircling a large exoplanet. The carbon-rich disk surrounding the world called CT Cha b, which is located 625 light-years away from Earth, is a possible construction yard for moons, although no moons are detected in the Webb data.
The young star the planet orbits is only 2 million years old and still accreting circumstellar material. However, the circumplanetary disk discovered by Webb is not part of the larger accretion disk around the central star. The two objects are 46 billion miles apart.
Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it. But we are only now entering an era where we can witness their formation.
This discovery fosters a better understanding of planet and moon formation, say researchers. Webb’s data is invaluable for making comparisons to our solar system’s birth over 4 billion years ago.
“We can see evidence of the disk around the companion, and we can study the chemistry for the first time. We’re not just witnessing moon formation — we’re also witnessing this planet’s formation,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington.
“We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zürich and member of the National Center of Competence in Research PlanetS.
Image A: Circumplanetary Disk (Artist’s Concept)
An artistic rendering of a dust and gas disk encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from NASA’s James Webb Space Telescope suggests the disk contains the raw materials for moon formation: diacetylene, hydrogen cyanide, propyne, acetylene, ethane, carbon dioxide, and benzene. The planet appears at lower right, while its host star and surrounding circumstellar disk are visible in the background.
Illustration: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zu00fcrich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)
Dissecting starlight
Infrared observations of CT Cha b were made with Webb’s MIRI (Mid-Infrared Instrument) using its medium resolution spectrograph. An initial look into Webb’s archival data revealed signs of molecules within the circumplanetary disk, which motivated a deeper dive into the data. Because the planet’s faint signal is buried in the glare of the host star, the researchers had to disentangle the light of the star from the planet using high-contrast methods.
“We saw molecules at the location of the planet, and so we knew that there was stuff in there worth digging for and spending a year trying to tease out of the data. It really took a lot of perseverance,” said Grant.
Ultimately, the team discovered seven carbon-bearing molecules within the planet’s disk, including acetylene (C2H2) and benzene (C6H6). This carbon-rich chemistry is in stark contrast to the chemistry seen in the disk around the host star, where the researchers found water but no carbon. The difference between the two disks offers evidence for their rapid chemical evolution over only 2 million years.
Genesis of moons
A circumplanetary disk has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites must have condensed out of such a flattened disk billions of years ago, as evident in their co-planar orbits about Jupiter. The two outermost Galilean moons, Ganymede and Callisto, are 50% water ice. But they presumably have rocky cores, perhaps either of carbon or silicon.
“We want to learn more about how our solar system formed moons. This means that we need to look at other systems that are still under construction. We’re trying to understand how it all works,” said Cugno. “How do these moons come to be? What are their ingredients? What physical processes are at play, and over what timescales? Webb allows us to witness the drama of moon formation and investigate these questions observationally for the first time.”
In the coming year, the team will use Webb to perform a comprehensive survey of similar objects, to better understand the diversity of physical and chemical properties in the disks around young planets.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
An artistic rendering of a dust and gas disk encircling the young exoplanet (lower right), CT Cha b, 625 light-years from Earth. Spectroscopic data from Webb suggests the disk contains the raw materials for moon formation.
NASA’s Webb Telescope Studies Moon-Forming Disk Around Massive Planet
An artistic rendering of a dust and gas disk encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Full image, annotation, and caption shown below.
Credits: Illustration: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zürich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)
NASA’s James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disk encircling a large exoplanet. The carbon-rich disk surrounding the world called CT Cha b, which is located 625 light-years away from Earth, is a possible construction yard for moons, although no moons are detected in the Webb data.
The young star the planet orbits is only 2 million years old and still accreting circumstellar material. However, the circumplanetary disk discovered by Webb is not part of the larger accretion disk around the central star. The two objects are 46 billion miles apart.
Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it. But we are only now entering an era where we can witness their formation.
This discovery fosters a better understanding of planet and moon formation, say researchers. Webb’s data is invaluable for making comparisons to our solar system’s birth over 4 billion years ago.
“We can see evidence of the disk around the companion, and we can study the chemistry for the first time. We’re not just witnessing moon formation — we’re also witnessing this planet’s formation,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington.
“We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zürich and member of the National Center of Competence in Research PlanetS.
Image A: Circumplanetary Disk (Artist’s Concept)
An artistic rendering of a dust and gas disk encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from NASA’s James Webb Space Telescope suggests the disk contains the raw materials for moon formation: diacetylene, hydrogen cyanide, propyne, acetylene, ethane, carbon dioxide, and benzene. The planet appears at lower right, while its host star and surrounding circumstellar disk are visible in the background.
Illustration: NASA, ESA, CSA, STScI, Gabriele Cugno (University of Zürich, NCCR PlanetS), Sierra Grant (Carnegie Institution for Science), Joseph Olmsted (STScI), Leah Hustak (STScI)
Dissecting starlight
Infrared observations of CT Cha b were made with Webb’s MIRI (Mid-Infrared Instrument) using its medium resolution spectrograph. An initial look into Webb’s archival data revealed signs of molecules within the circumplanetary disk, which motivated a deeper dive into the data. Because the planet’s faint signal is buried in the glare of the host star, the researchers had to disentangle the light of the star from the planet using high-contrast methods.
“We saw molecules at the location of the planet, and so we knew that there was stuff in there worth digging for and spending a year trying to tease out of the data. It really took a lot of perseverance,” said Grant.
Ultimately, the team discovered seven carbon-bearing molecules within the planet’s disk, including acetylene (C2H2) and benzene (C6H6). This carbon-rich chemistry is in stark contrast to the chemistry seen in the disk around the host star, where the researchers found water but no carbon. The difference between the two disks offers evidence for their rapid chemical evolution over only than 2 million years.
Genesis of moons
A circumplanetary disk has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites must have condensed out of such a flattened disk billions of years ago, as evident in their co-planar orbits about Jupiter. The two outermost Galilean moons, Ganymede and Callisto, are 50% water ice. But they presumably have rocky cores, perhaps either of carbon or silicon.
“We want to learn more about how our solar system formed moons. This means that we need to look at other systems that are still under construction. We’re trying to understand how it all works,” said Cugno. “How do these moons come to be? What are their ingredients? What physical processes are at play, and over what timescales? Webb allows us to witness the drama of moon formation and investigate these questions observationally for the first time.”
In the coming year, the team will use Webb to perform a comprehensive survey of similar objects, to better understand the diversity of physical and chemical properties in the disks around young planets.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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