Telescópio Espacial James Webb identified the presence of methane gas being released by the interstellar comet 3I/ATLAS. The study, published in the scientific journal The Astrophysical Journal Letters, points out that this is the first time that the chemical compound has been recorded on a visiting celestial body from outside Sistema Solar. The object is on its way out of our cosmic neighborhood.
The detection surprised researchers because of the unusual chemical signature presented by the interstellar comet. The data collected shows that the amount of methane in relation to water present in the celestial body is significantly higher than the rate observed in native Sistema Solar comets. Essa discovery reinforces the astronomical thesis that 3I/ATLAS was formed in a region of the universe with environmental and chemical conditions quite different from those that gave rise to the planets and smaller bodies that orbit Sol.
James Webb monitored interstellar comet in two distinct stages
The space observations concentrated on 3I/ATLAS initially took place between December 15th and 16th, 2025. Naquela Opportunity, the team of scientists used the Instrumento of Infravermelho Médio, known by the acronym MIRI, coupled to the Telescópio Espacial James Webb, operated by NASA in cooperation with the ESA and CSA agencies. The interstellar comet was located at an estimated distance of 330 million kilometers from Sol, two months after reaching its closest approach to the star.
A technical failure affected part of the data capture schedule scheduled for mid-December, forcing astronomers to carry out a new recording session on December 27, 2025. In the second round of analyses, the interstellar comet had already moved to a distance of approximately 380 million kilometers from Sol. The technical setback ended up turning into a positive scientific opportunity for the group of researchers. The team was able to directly compare changes in the interstellar comet’s outgassing activity at two different moments in its receding trajectory.
Aquecimento solar altered release of chemical compounds on the surface
The point of greatest proximity of the interstellar comet to Sol, called perihelion, caused strong overheating in the surface layer of 3I/ATLAS. Esse extreme thermal increase modified the evaporation structure of the celestial body’s frozen elements. When crossing the data obtained on the two dates in December, the scientists noticed that the rate of water evaporation decreased markedly as the object moved away from the solar heat.
The infrared data revealed unexpected behavior in the other chemical elements studied by astronomers:
- Methane release remained stable even with increasing distance from Sol.
- Carbon dioxide kept its emission levels unchanged in the two December observations.
- The proportion of methane exceeded the standards cataloged in comets generated in Sistema Solar.
- Three-dimensional chemical maps recorded the persistence of gases around the nucleus.
The evaporation stability of these specific compounds indicates that the methane and carbon dioxide were likely released from the deep, inner layers of the interstellar comet. Essas denser rock fractions were heated in a delayed and lasting manner by the impact of solar radiation received during perihelion. The physical process caused gases to continue escaping into space even as the outer crust began to cool due to the star’s progressive movement away.
Descoberta indicates great diversity of planetary systems in Via Láctea
The chemical composition found in 3I/ATLAS opens a new window of understanding on how planetary systems develop in other areas of the galaxy. Cometas are considered space fossils that preserve the original materials of the nebula that generated each system. The abundance of methane indicates that the birthplace of this interstellar comet had carbon and hydrogen stores organized differently than our own planetary system.
Researchers associated with the project continue to process the information collected by James Webb’s spectrograph to map other possible volatile components in the interstellar comet’s tail. Como 3I/ATLAS moves at a speed that will permanently eject it from Sistema Solar, the current period represents the last opportunity for ground and space telescopes to extract direct data on the geology of this cosmic visitor. Astronomers hope that models of interstellar chemical evolution will be revised based on data published this week.
