💧 3I/ATLAS: The object from elsewhere has begun seeding our solar system

Observations made by NASA's Neil Gehrels Swift Space Observatory have revealed that the interstellar object 3I/ATLAS currently passing through our Solar System is emitting hydroxyl gas.

This is a byproduct of water caused by ultraviolet radiation. Researchers calculated that comet 3I/ATLAS is losing about 40 kilograms of water every second (approximately 88 pounds), a flow rate comparable to a powerful water jet. This early water activity suggests that the internal composition of this comet fundamentally differs from that of comets native to our Solar System.


Preliminary studies from the James Webb Space Telescope had already indicated that this comet exhibited a high ratio of carbon dioxide to water. The new research published in The Astrophysical Journal Letters confirms this chemical singularity. Scientists believe this early outgassing could be caused by the warming of small ice grains on the surface of the cometary nucleus due to solar radiation, even at great distances.


Dennis Bodewits, co-author of the study and physics professor at Auburn University, explains that detecting water in an interstellar comet is equivalent to receiving a chemical message from another planetary system. This discovery indicates that the ingredients necessary for the chemistry of life are not exclusive to our cosmic environment. The presence of water, an essential molecule for the development of life as we know it, in objects coming from other stellar systems opens perspectives for learning more about the distribution of prebiotic elements.

3I/ATLAS represents only the third interstellar visitor ever recorded, after 1I/'Oumuamua in 2017 and 2I/Borisov in 2019. Each of these comets has presented distinct characteristics: 'Oumuamua was relatively dry, Borisov was rich in carbon monoxide, and now 3I/ATLAS is releasing water upon its arrival in our Solar System. This diversity among interstellar objects shows the existence of multiple planetary and cometary formation environments in our Galaxy, each producing celestial bodies with unique chemical properties.


Zexi Xing, lead researcher of the study, emphasizes that every interstellar object discovered so far has brought its share of surprises and changed our understanding of planet and comet formation processes around stars. These cosmic visitors offer us direct samples of materials from other stellar systems, allowing astronomers to directly study the chemical composition of distant regions of our Milky Way without having to send space missions there.

Hydroxyl gas: tracer of water in space

Hydroxyl gas (OH) represents a valuable indicator for detecting the presence of water in interstellar space. This molecule forms when the Sun's ultraviolet rays break water molecules (H2O) into hydrogen atoms and hydroxyl radicals.

Astronomers use the characteristic ultraviolet signature of hydroxyl to locate water at considerable distances, as OH gas emits specific light when excited by stellar radiation. This technique allows for indirect detection of water even when instruments cannot directly observe H₂O molecules.

In the case of comet 3I/ATLAS, the detection of hydroxyl gas at 2.9 astronomical units from the Sun revealed exceptionally early water activity. This indirect detection method proves particularly useful for studying comets and other celestial bodies where water may be present in different forms.

The study of hydroxyl also provides information about photochemical processes occurring in space environments, helping scientists understand how complex organic molecules might form and evolve in different planetary systems.