A messenger from another star system, carrying within its structure a record of how planets form elsewhere
The comet ejects ~70 Olympic pools of water vapor daily through sublimation triggered by solar radiation near perihelion in October 2025. Unusual concentrations of methanol and organic molecules differ from solar system comets, indicating formation in a distinct chemical environment from early galactic epochs.
- 3I/Atlas ejects approximately 2 tons of material per second, equivalent to 70 Olympic pools of water vapor daily
- The comet is estimated to be between 10 and 12 billion years old, with isotopic composition linked to early Milky Way formation
- Observations made by JUICE's MAJIS and JANUS instruments in November 2025, received on Earth in February 2026
- The comet follows a hyperbolic trajectory and will not return to the solar system
ESA's JUICE mission detected comet 3I/Atlas releasing 2 tons of material per second, revealing chemical signatures from the early Milky Way and suggesting an origin 10-12 billion years old.
In October 2025, as the interstellar comet 3I/Atlas made its closest approach to the Sun, Europe's JUICE spacecraft trained its instruments on the ancient visitor and watched it come apart. Two tons of material per second were streaming into space—roughly seventy Olympic swimming pools worth of water vapor ejected each day. The observations, collected in November 2025 and transmitted back to Earth by February 2026, offered humanity its first detailed look at a comet born around another star billions of years ago.
The JUICE mission's MAJIS and JANUS instruments detected the comet's violent outgassing as solar radiation heated its frozen nucleus. Buried ices of water and carbon dioxide, locked inside the comet since its formation, suddenly sublimated—transforming directly from solid to gas. The process created a visible coma around the nucleus, a trailing tail, and a brightening that made the distant object detectable from Earth. Giuseppe Piccioni, a researcher at Italy's National Institute for Astrophysics, explained that the repeated detections of water vapor and carbon dioxide revealed how volatile materials buried deep within the comet were being liberated into space in the weeks following perihelion. The data suggested a mass loss rate of approximately two tons per second—a staggering figure that underscored the comet's violent awakening.
What made 3I/Atlas scientifically extraordinary was not just the quantity of material it was shedding, but what that material revealed about its origins. Recent analyses, drawing on observations from the James Webb and Hubble space telescopes, suggested the comet was between ten and twelve billion years old—placing it among the most ancient objects ever observed. Its isotopic composition pointed to formation during the early epochs of the Milky Way itself. More striking still were the chemical signatures embedded in its structure. The comet contained unusually high concentrations of methanol and organic molecules in proportions that differed markedly from comets native to our solar system. These differences indicated that 3I/Atlas had formed in a fundamentally different chemical environment, one shaped by conditions that existed in a distant stellar neighborhood billions of years in the past.
Pasquale Palumbo, the principal investigator for the JANUS instrument, described the moment the data arrived as vindication for the long wait. The images revealed an object of stunning complexity—an extended coma, a pronounced tail, and intricate structures including jets, rays, and filaments streaming from the nucleus. These features would allow scientists to study how the comet's behavior evolved as it moved through different regions of space and experienced varying levels of solar heating. Palumbo noted that the JANUS performance during this encounter offered a preview of what the instrument would accomplish when JUICE eventually reached Jupiter and its icy moons.
The discovery of 3I/Atlas itself had come on July 1, 2025, but the window for detailed observation was narrow and the signals faint. The data transmission back to Earth consumed months. Yet the wait proved worthwhile. The observations provided the first clear evidence of the comet's intense activity near perihelion, capturing a moment when an object that had traveled through interstellar space for billions of years was being fundamentally transformed by proximity to a star.
In the months before these observations were confirmed, speculation had swirled about whether 3I/Atlas might be artificial in origin. The comet's periodic brightness variations, its detected emissions, and certain features that seemed unusual had prompted some researchers, including astrophysicist Avi Loeb, to propose that it might be a technological artifact. Subsequent analysis, however, attributed all of these characteristics to natural cometary processes—the predictable outgassing and structural changes that occur when a frozen body approaches a star. The scientific community and space agencies including NASA now regard 3I/Atlas as unambiguously natural, a pristine sample of interstellar material.
As of now, 3I/Atlas continues its journey outward on a hyperbolic trajectory that will carry it beyond the orbits of Saturn, Uranus, and Neptune, never to return to the inner solar system. Astronomers continue to track its position and brightness as it recedes, knowing that this window into the chemical composition of the early galaxy will eventually close. The comet represents a rare opportunity—a messenger from another star system, carrying within its structure a record of how planets and comets formed in a different corner of the universe, now passing through our neighborhood and offering its secrets before it vanishes into the dark.
Citações Notáveis
The volatile ices buried under the surface were released actively into space shortly after the comet's closest approach to the Sun, with an outflow rate of approximately two tons per second.— Giuseppe Piccioni, National Institute for Astrophysics
The images reveal for the first time the intense activity of the comet near perihelion, showing an extended coma, tail, and various structures like jets and filaments that will allow us to study its evolution over different time periods.— Pasquale Palumbo, JANUS instrument principal investigator
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that this comet is so old? We've studied old things before.
Because this one carries a chemical fingerprint from a different star system, from a time when the galaxy itself was young. It's not just old—it's a sample of somewhere else, preserved in ice for billions of years.
The two tons per second figure—is that unusual for a comet?
For a comet passing close to the Sun, no. But the composition of what's being ejected is what's striking. The methanol and organic molecules are in proportions we don't see in our own solar system's comets. That tells us something about the environment where this one formed.
So it's leaving the solar system now. Does that mean we've lost our chance to study it?
Mostly, yes. The brightness is fading as it moves away. But the data JUICE collected during that close pass—the images, the chemical readings—that's the record we have. It's enough to ask fundamental questions about how planets form around other stars.
There was talk of it being artificial. What changed people's minds?
The behavior that seemed unusual—the brightness variations, the jets—turned out to be exactly what you'd expect from a frozen body heating up near a star. Once you understand the physics, the mystery dissolves. It's natural, just foreign.
What happens to the data now?
Scientists will spend years analyzing it. Every molecule detected, every structural feature in those images—it all becomes part of our understanding of how chemistry works in the early universe. This comet becomes a reference point for studying exoplanetary systems we can't yet visit.