Astronomers say they have confirmed the presence of water ice in a planetary system beyond our own for the first time, in the latest major discovery made possible by NASA’s James Webb Space Telescope (JWST).
The discovery, which astronomers have demonstrated to be water in the form of crystalline ice, and not just as water vapor, marks a significant milestone in the long-running search for evidence of water ice in distant star systems.
Although it has long been suspected that frozen water exists in other solar systems, past observations of suspected examples involved only indirect evidence.
Now, that has all changed thanks to Webb’s highly sensitive instruments, which confirmed crystalline water within the dusty debris disk surrounding HD 181327, a Sun-like star located 155 light-years away. The landmark confirmation follows a series of significant discoveries made by Webb, which include the successful detection of unexpected auroral activity near Jupiter’s poles.
Confirming Decades of Predictions
The new discovery validates decades of theoretical predictions and opens new pathways toward understanding the dynamics of planetary formation and whether conditions for life might be more common throughout the cosmos than past astronomical observations may have conveyed.
Intricately mixed amid fine dust particles in HD 181327’s surrounding debris, the water ice is believed to comprise miniature “dirty snowballs” that astronomers say are scattered throughout the star’s expansive disk.
“Webb unambiguously detected not just water ice, but crystalline water ice, which is also found in locations like Saturn’s rings and icy bodies in our solar system’s Kuiper Belt,” said Chen Xie, assistant research scientist at Johns Hopkins University and the lead author of a new paper detailing the findings.
Water Ice Around HD 181327
Astronomers estimate HD 181327 to be just 23 million years old. That, in comparison to our Sun, makes it relatively young—possibly just 23 million years old, compared to our 4.6 billion-year-old host star.
HD 181327 is also slightly larger and hotter than the Sun, possessing a significantly wider debris disk with a noticeable gap near the star. Like our planetary system, an outer region of HD 181327’s disk resembles the rocky area beyond Neptune known as the Kuiper Belt.
The outermost regions of HD 181327 disk have the coldest temperatures, harboring the most abundant stores of water ice, which Xie and the research team behind the landmark discovery believe could be as much as 20% in certain regions.
Intense Ultraviolet Radiation
Looking closer to the star, less evidence of ice seemed to be present, with only around 8% in the middle region of the disk, and virtually none within the innermost area. This absence of ice could result from intense ultraviolet radiation that vaporizes any water particles that make their way close to the star’s surface.
Another possibility is that larger rocky bodies, known as planetesimals, might be trapping frozen water within their interiors, making it presently undetectable even by Webb’s most sensitive instruments.
New Clues to Early Planet Formation
The team’s findings are significant and far-reaching since the presence of water ice plays a critical role during the earliest stages of planet formation. Astronomers believe this frozen water may eventually make its way to emerging terrestrial planets by hitching rides on comet-like bodies, which may seed them with not only water but possibly other components crucial to forming habitable worlds.
“When I was a graduate student 25 years ago, my advisor told me there should be ice in debris disks, but prior to Webb, we didn’t have instruments sensitive enough to make these observations,” said the study’s co-author, Christine Chen, of the Space Telescope Science Institute.
After many years of speculation, Webb’s Near-Infrared Spectrograph (NIRSpec) has finally provided the crucial data needed to confirm these long-held theories. Additionally, Webb’s NIRSpec can detect the faintest traces of dust and ice, unlike past space observatories that previous instruments, such as the now-retired Spitzer Space Telescope, could only hint at.
Accumulation of Water Ice Over Time
Over time, collisions between icy bodies within HD 181327’s debris disk will continue to produce fine particles that Webb’s sensitive camera eyes can discern, leading to additional discoveries in the years to come.
“Icy materials may also ultimately be ‘delivered’ to terrestrial planets that may form over a couple hundred million years in systems like this,” Xie notes.
For now, with the confirmed presence of frozen water ice in a planetary system beyond ours, astronomers plan to study other debris disks and young planetary systems throughout the Milky Way in search of additional signs that water—and possibly even life—may be lurking in our galaxy, hidden from astronomers due to the technological limitations of past space observatories.
The team’s new paper, “Water ice in the debris disk around HD 181327,” appeared in Nature on May 14, 2025.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.