Comet 3I/ATLAS has developed a deep irradiated crust that no longer resembles material from its home star system, according to new research using James Webb Space Telescope observations and computer simulations. The study, posted to the preprint server arXiv on Friday (Oct. 31), has not yet undergone peer review.
Researchers determined the comet's documented "extreme" carbon dioxide (CO2) enrichment levels resulted from space radiation absorbed during its estimated 7-billion-year lifespan. Analysis indicates cosmic rays have significantly altered the physical state of the comet's ice down to depths of approximately 50 to 65 feet (15 to 20 meters).
"It's very slow, but over billions of years, it's a very strong effect," study lead author Romain Maggiolo, a research scientist at the Royal Belgian Institute for Space Aeronomy, told Live Science.
Also read: 3I/ATLAS alien ship engine in overdrive? Harvard scientist claims interstellar comet is driven by ‘non-gra
Galactic cosmic rays convert carbon monoxide to carbon dioxide in interstellar space
Galactic cosmic rays, high-energy particles originating outside the solar system, strike carbon monoxide (CO) in space to convert it to carbon dioxide (CO2). The heliosphere, an enormous bubble of radiation emitted by the sun, shields Earth and neighboring planets from most cosmic radiation. In interstellar space, where 3I/ATLAS spent most of its existence, no protective barrier exists against this space radiation.
The Milky Way's interstellar environment exposed the comet to continuous cosmic ray bombardment throughout its journey before entering the solar system.
The researchers described their findings as a "paradigm shift" for studying interstellar objects. The results suggest objects like comet 3I/ATLAS consist primarily of galactic cosmic ray-processed material rather than pristine matter representative of their formation environments. The comet's exterior reflects its interstellar journey rather than its origin point.
Comet 3I/ATLAS reached perihelion after discovery in July
Comet 3I/ATLAS reached perihelion, its closest point to the sun, on Thursday (Oct. 29). Since its discovery in July, researchers have used various telescopes to study the interstellar visitor. Comets heat up near stars, causing surface ices to sublimate into gas.
The new findings indicate gases ejected from the comet before perihelion originated from its irradiated outer shell. This pattern likely continues post-perihelion, though Maggiolo noted solar erosion might potentially expose pristine materials from the comet's home star locked in its nucleus.
"It will be very interesting to compare observations before perihelion, so the first observation we had when it arrived in the solar system, with observations made after perihelion when there was some erosion," Maggiolo said. "Maybe by looking at these differences, we can have some indication about its initial composition."
Comet travels through solar system at 130,000 mph in flat trajectory
Research findings indicate comet 3I/ATLAS travels through the solar system at speeds exceeding 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory. One study suggests the comet may be the oldest comet ever observed, approximately 3 billion years older than the 4.6-billion-year-old solar system.
The research builds on previous work documenting comet 3I/ATLAS' CO2-rich composition based on James Webb Space Telescope's first images of the interstellar visitor in August. Observations from NASA's SPHEREx orbiter, also conducted in August, provided additional data on the comet's chemical composition.
Also read: 3I/ATLAS huge breakthrough: NASA detects Fingerprint of Water — Does it confirm life beyond Earth?
Computer simulations modeled billion years of cosmic ray exposure effects
Maggiolo and colleagues adapted models from their 2020 study published in The Astrophysical Journal Letters, originally used to examine comet 67P, which orbits between Jupiter and Earth. The team modeled cumulative effects of galactic cosmic ray exposure on ice structure and chemical composition after 1 billion years of irradiation.
The methodology relies on laboratory experiments simulating galactic cosmic ray effects. While these tests may not completely represent interstellar conditions, they provide indicators of what comets experience during multibillion-year journeys through interstellar space, according to the study.
One billion years of irradiation sufficient for deep crust formation
Simulations determined 1 billion years of irradiation was sufficient for comet 3I/ATLAS to form its deep irradiated crust. Maggiolo noted the comet contains valuable scientific information despite aging and transformation during its interstellar journey. Researchers must account for these aging processes during analysis.
"We have to be careful and take into account aging processes, so it's more work for scientists, but [3I/ATLAS] remains very interesting," Maggiolo said.
Researchers determined the comet's documented "extreme" carbon dioxide (CO2) enrichment levels resulted from space radiation absorbed during its estimated 7-billion-year lifespan. Analysis indicates cosmic rays have significantly altered the physical state of the comet's ice down to depths of approximately 50 to 65 feet (15 to 20 meters).
"It's very slow, but over billions of years, it's a very strong effect," study lead author Romain Maggiolo, a research scientist at the Royal Belgian Institute for Space Aeronomy, told Live Science.
Also read: 3I/ATLAS alien ship engine in overdrive? Harvard scientist claims interstellar comet is driven by ‘non-gra
Galactic cosmic rays convert carbon monoxide to carbon dioxide in interstellar space
Galactic cosmic rays, high-energy particles originating outside the solar system, strike carbon monoxide (CO) in space to convert it to carbon dioxide (CO2). The heliosphere, an enormous bubble of radiation emitted by the sun, shields Earth and neighboring planets from most cosmic radiation. In interstellar space, where 3I/ATLAS spent most of its existence, no protective barrier exists against this space radiation.
The Milky Way's interstellar environment exposed the comet to continuous cosmic ray bombardment throughout its journey before entering the solar system.
The researchers described their findings as a "paradigm shift" for studying interstellar objects. The results suggest objects like comet 3I/ATLAS consist primarily of galactic cosmic ray-processed material rather than pristine matter representative of their formation environments. The comet's exterior reflects its interstellar journey rather than its origin point.
Comet 3I/ATLAS reached perihelion after discovery in July
Comet 3I/ATLAS reached perihelion, its closest point to the sun, on Thursday (Oct. 29). Since its discovery in July, researchers have used various telescopes to study the interstellar visitor. Comets heat up near stars, causing surface ices to sublimate into gas.
The new findings indicate gases ejected from the comet before perihelion originated from its irradiated outer shell. This pattern likely continues post-perihelion, though Maggiolo noted solar erosion might potentially expose pristine materials from the comet's home star locked in its nucleus.
"It will be very interesting to compare observations before perihelion, so the first observation we had when it arrived in the solar system, with observations made after perihelion when there was some erosion," Maggiolo said. "Maybe by looking at these differences, we can have some indication about its initial composition."
Comet travels through solar system at 130,000 mph in flat trajectory
Research findings indicate comet 3I/ATLAS travels through the solar system at speeds exceeding 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory. One study suggests the comet may be the oldest comet ever observed, approximately 3 billion years older than the 4.6-billion-year-old solar system.
The research builds on previous work documenting comet 3I/ATLAS' CO2-rich composition based on James Webb Space Telescope's first images of the interstellar visitor in August. Observations from NASA's SPHEREx orbiter, also conducted in August, provided additional data on the comet's chemical composition.
Also read: 3I/ATLAS huge breakthrough: NASA detects Fingerprint of Water — Does it confirm life beyond Earth?
Computer simulations modeled billion years of cosmic ray exposure effects
Maggiolo and colleagues adapted models from their 2020 study published in The Astrophysical Journal Letters, originally used to examine comet 67P, which orbits between Jupiter and Earth. The team modeled cumulative effects of galactic cosmic ray exposure on ice structure and chemical composition after 1 billion years of irradiation.
The methodology relies on laboratory experiments simulating galactic cosmic ray effects. While these tests may not completely represent interstellar conditions, they provide indicators of what comets experience during multibillion-year journeys through interstellar space, according to the study.
One billion years of irradiation sufficient for deep crust formation
Simulations determined 1 billion years of irradiation was sufficient for comet 3I/ATLAS to form its deep irradiated crust. Maggiolo noted the comet contains valuable scientific information despite aging and transformation during its interstellar journey. Researchers must account for these aging processes during analysis.
"We have to be careful and take into account aging processes, so it's more work for scientists, but [3I/ATLAS] remains very interesting," Maggiolo said.
