The recent discovery by scientists from Belgium and the U.S.A. regarding the interstellar comet 3I/ATLAS constitutes one of the most important developments in astronomy in recent years.
This comet, which passed close to the Sun in 2025, bears a crust made of organic and other carbon-containing compounds that formed on its surface due to prolonged exposure to cosmic rays in interstellar space.
This discovery not only challenges many existing notions about interstellar objects but also opens new avenues for understanding the evolution of comets and other small bodies in space.
What is comet 3I/ATLAS?
3I/ATLAS is the third interstellar comet discovered by astronomers and the first to pass close to the Sun in 2025.
Its discovery was made by NASA’s automated telescope network ATLAS, whose main goal is to monitor potentially hazardous asteroids and other small space bodies that approach Earth.
The comet, like the other two interstellar visitors discovered previously — the asteroid ‘Oumuamua in 2017 and the comet 2I/Borisov in 2019 — originates from a region far beyond our solar system, which makes it extremely interesting for study.
The desire to better understand interstellar comets is of great importance, as these comets can contain valuable information about the early phases of the Solar System and the possible existence of organic matter in space.
The discovery of the organic crust
The study of 3I/ATLAS, using the James Webb Telescope and SPHEREx, revealed an astonishing discovery about the composition of the comet’s surface.
The team of astronomers, led by Romain Maggiolo from the Royal Institute for Space Astronomy of Belgium, observed that the comet is covered by a thick crust of organic and other carbon-containing materials.
This crust was formed by the prolonged exposure of the comet to cosmic rays in interstellar space, even before it reached our solar system.
The observation of this “organic crust” is crucial for understanding the process that occurs when interstellar objects interact with the energy of cosmic rays.
As the data indicate, these organic materials have undergone significant modification and have been transformed into new compounds due to continuous exposure to high-energy particles such as cosmic rays.
The impact of cosmic rays on the composition of interstellar objects
This discovery brings a revolution to our perceptions of interstellar objects.
According to observations, exposure to cosmic rays has caused the transformation of carbon monoxide (CO) into carbon dioxide (CO₂), while simultaneously forming an organic crust on the comet’s surface.
This means that interstellar objects are not merely remnants of the primordial materials of the stellar systems in which they were born but have undergone significant changes in interstellar space.
The development of these organic layers on interstellar comets provides new information about the effects of cosmic rays and other interstellar environmental factors on the evolution of celestial bodies.
The study’s results show that this organic crust is approximately 15–20 meters thick, challenging the idea that interstellar objects remain unchanged and unaltered from their formation until they reach our solar system.
On the contrary, these findings highlight the importance of the interstellar environment in altering the composition of such objects.
Characteristics and particularities of comet 3I/ATLAS
3I/ATLAS possesses several interesting characteristics that make it unique. Apart from the large amount of carbon dioxide (CO₂) it emits — unusual for comets of the solar system — astronomers also observed high concentrations of carbon monoxide (CO) in its emissions.
This, combined with the “red” spectrum observed by telescopes, demonstrates that this comet is different from those we are accustomed to observing within our solar system.
These data also suggest that 3I/ATLAS may have formed from materials that do not originate from the same type of stellar system as the comets of our solar system, but perhaps as a result of encountering exoplanetary materials that underwent transformation due to cosmic rays.
Possible developments
This discovery opens new paths for the study of interstellar objects.
Astronomers will continue to monitor 3I/ATLAS and other interstellar comets with new observations and analyses in order to fully understand the processes that affect their evolution.
The use of new, more advanced telescopes such as James Webb and SPHEREx is expected to provide valuable information about the composition and structure of these mysterious objects.
Understanding how cosmic rays affect interstellar objects and how these bodies transform over time could bring revolutionary changes to the science of astronomy, as we analyze the earliest stages of the formation and evolution of celestial bodies beyond our solar system.
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