An Alien Visitor Creating Planetary-Scale Phenomena
A visitor from another star system is rewriting what we thought we knew about space objects. 3I/ATLAS, with a nucleus size that remains uncertain but is likely somewhere between a few kilometers to potentially tens of kilometers across, is creating a gas cloud that extends at least 348,000 kilometers into space. To put that in perspective: this alien object has generated an envelope that reaches nearly 91% of the way to the Moon.
Two of humanity's most advanced space telescopes have been watching 3I/ATLAS, and what they're seeing challenges everything we understand about objects from beyond our Solar System. The question isn't just what this thing is doing, but what exactly it is.
Two Telescopes, One Shocking Discovery
Between August 6 and 12, 2025, both NASA's James Webb Space Telescope (JWST) and the SPHEREx observatory captured simultaneous observations of 3I/ATLAS. What they found was unprecedented in the history of astronomy.
SPHEREx detected a bright CO₂ gas envelope extending at least 348,000 kilometers from the nucleus, while JWST revealed the detailed chemistry driving this massive phenomenon. The scale is extraordinary: even if the nucleus is tens of kilometers across, it's creating a gas envelope thousands of times larger than itself.
This isn't just unusual, it's statistically impossible for normal Solar System objects. The chemistry and behavior of 3I/ATLAS represent something we've never encountered before.
Alien Chemistry From Another Star System
The detailed spectroscopic analysis from JWST reveals just how foreign 3I/ATLAS really is. The object has a CO₂ to H₂O ratio of 8.0 ± 1.0, meaning it's pumping out eight times more carbon dioxide than water vapor. SPHEREx observations confirm this unusual CO₂ dominance with production rates of 9.4 × 10²⁶ molecules per second. For context, this ratio is so unusual that it sits 6.1σ above the trend observed in all known Solar System objects.
In scientific terms, a 6.1σ deviation means this is a one-in-several-million occurrence if 3I/ATLAS were a normal object. Only one other object in history, the peculiar C/2016 R2 (PanSTARRS), famous for its unusual hypervolatile composition, has shown similarly extreme chemistry.
Key Points
- CO₂/H₂O ratio of 8:1 (vs typical ratios much closer to 1:1 or lower)
- Age estimated at 3 to 11 billion years old
- Chemistry indicating formation around a different star with different conditions
- Pumping out nearly 2 quintillion gas molecules every second
What we're witnessing is genuine alien matter, chemistry that formed light-years away under stellar conditions completely different from our Sun.
The Scale Defies Imagination
While JWST focused on detailed chemistry, SPHEREx's wide field of view revealed the true scope of 3I/ATLAS's activity. The CO₂ gas envelope extends to at least 348,000 kilometers from the nucleus.
To grasp this scale:
- The nucleus size remains debated: JWST data suggests less than 5.6 km diameter, while SPHEREx estimates up to 46 km diameter
- The gas cloud extends nearly 91% of the way to the Moon
- Even with the larger size estimates, this represents a size ratio of thousands to one between the gas envelope and the solid nucleus
- SPHEREx notes that over 99% of the observed light comes from coma dust rather than the nucleus itself
The object is producing 12 to 120 kilograms of dust per second, essentially losing the mass of a small car every few seconds to couple of minutes. Yet this tiny active area (just 2.6% of the total surface) is sufficient to create and maintain this massive planetary-scale phenomenon.
What Are We Actually Looking At?
3I/ATLAS originates from beyond our Solar System, with dynamical modeling suggesting it could be 3 to 11 billion years old. This makes it potentially older than our entire Solar System, carrying chemistry from an ancient stellar environment we can barely imagine.
The object likely formed in what astronomers call the "thick disk" population of our galaxy, a region populated by older, more metal-poor stars. The unusual CO₂ dominance might result from formation close to the CO₂ ice line in its parent protoplanetary disk, or from exposure to higher levels of radiation than typical Solar System objects experience.
We're not just looking at a space rock, we're observing active alien chemistry in real-time, watching matter from another star system interact with our Sun's radiation and solar wind.
So What Exactly Is 3I/ATLAS?
Here's where things get interesting. Despite its radical departure from normal behavior, most characteristics of 3I/ATLAS still point toward it being a natural object, albeit one formed under completely alien conditions. It shows clear signs of volatile outgassing, dust production, and thermal response to solar heating, all consistent with a highly unusual but natural body.
However, being so fundamentally different from anything in our Solar System, we cannot completely rule out more exotic explanations. The possibility of artificial origin, while remote, cannot be dismissed purely on the basis of current observations.
The Reality Check: We haven't observed any "intelligent" behaviors in 3I/ATLAS. There have been no sudden accelerations, course corrections, or organized patterns that would suggest technology rather than natural processes. Its activity appears to follow predictable patterns based on solar heating and volatile sublimation.
The most likely explanation remains that 3I/ATLAS is an extraordinary natural object, a genuine alien visitor that formed under stellar conditions so different from our own Sun that its chemistry and behavior appear almost impossible by Solar System standards.
The Bigger Picture
The simultaneous observations by JWST and SPHEREx represent a watershed moment in astronomy. For the first time, we have detailed chemical and physical data on an active interstellar visitor, providing direct evidence of planetary formation processes around other stars.
However, the conflicting size estimates raise fundamental questions that challenge our understanding of both observation methods and object behavior:
If 3I/ATLAS is actually large (46 km diameter): How did we miss detecting such a massive object until it reached Jupiter's orbit? Objects of this size should be detectable much earlier in their approach to the inner Solar System. Current asteroid and comet surveys regularly detect much smaller objects at greater distances, so missing a 46-kilometer object suggests either extraordinary circumstances or limitations in our detection capabilities for interstellar visitors.
If 3I/ATLAS is actually small (under 6 km diameter): How can we explain its exceptional brightness and massive gas production? The object is producing 12 to 120 kilograms of dust per second and maintaining a gas envelope that extends hundreds of thousands of kilometers. Small objects typically cannot sustain such intense activity levels, raising questions about its internal composition or energy sources.
This size uncertainty isn't just an academic debate, it has profound implications for how we search for and study future interstellar visitors. The answer will determine whether we need to revise our detection strategies, our understanding of volatile outgassing mechanics, or both.
The discovery validates theoretical models suggesting that interstellar space should be populated with ejected planetesimals from other star systems. More importantly, it demonstrates that these visitors carry direct samples of alien stellar chemistry that we can study in unprecedented detail.
As 3I/ATLAS continues its approach toward the Sun, additional telescopes worldwide are joining the observation campaign. Whether it turns out to be an exotic natural object or something even more extraordinary, we are witnessing our first detailed study of truly alien matter in action.
The universe just got a lot more interesting, and a lot more puzzling.
Sources and Data
This analysis is based on simultaneous observations from two major space observatories: detailed spectroscopic data from the James Webb Space Telescope published in Cordiner et al. 2025, and wide-field observations from SPHEREx detailed in their research notice. Both datasets were collected during the same observation window in August 2025, providing complementary views of this unprecedented interstellar visitor.
