Harvard astrophysicist Avi Loeb has urged astronomers and space agencies to monitor a newly observed interstellar visitor — designated 3I/ATLAS — as it passes through our solar system, warning it could be an artificial object or release small probes. The object was first detected earlier this year and is on track to make its closest approach to the Sun next month before exiting the system. Most researchers currently interpret 3I/ATLAS as a comet, and images from the Gemini South telescope in Chile show a growing tail as the object sublimates dust and gas. Loeb, however, has repeatedly called for targeted observations by instruments such as NASA’s Mars Reconnaissance Orbiter and Juno probe to watch for any unexpected activity.
Key Takeaways
- 3I/ATLAS is an interstellar visitor first seen earlier this year and will make perihelion (closest approach to the Sun) next month.
- Observations from Gemini South show an expanding tail, supporting the mainstream interpretation that the object is cometary in nature.
- Avi Loeb has suggested the object could be as large as 28.5 miles across, an estimate he says would make it far more massive than previously known interstellar objects.
- Loeb has requested NASA repoint assets including the Mars Reconnaissance Orbiter and Juno to observe the object as it passes nearby several planets.
- Trajectory analyses note that 3I/ATLAS will come within roughly 1.67 million miles of Mars’ orbit, a close approach some observers describe as unusually fine-tuned.
- Scientific consensus remains that a natural cometary origin is the most likely explanation, though proponents of alternative hypotheses argue targeted monitoring is warranted.
Background
Interest in interstellar visitors rose sharply after detections of 1I/2017 Uumuamua and 2I/Borisov. Those objects triggered intense debate about formation, composition and the limits of remote observation, and they shaped how the community approaches new detections from beyond the Solar System. Most professional teams adopt conservative, natural explanations unless data force a different conclusion; comets and icy bodies that outgas when warmed are a familiar category that explains many observed behaviors. Avi Loeb, a well-known figure in that debate, has for years encouraged open consideration of technosignature hypotheses and has urged investment in targeted observations when anomalous objects appear.
Spacecraft assets such as NASA’s Mars Reconnaissance Orbiter and the Juno probe routinely collect planetary data but can be retasked for opportunistic observations when mission teams approve. Ground-based facilities and survey telescopes are the first line of detection, but closer in situ monitoring — or at least high-resolution remote sensing — can provide critical constraints on composition, morphology and any transient phenomena. The scientific community balances limited resources, instrumentation capabilities and mission priorities when deciding whether to repoint a spacecraft. That calculus becomes more urgent when an object’s path carries it near planets or through regions where released material might be detectable.
Main Event
After its discovery earlier this year, 3I/ATLAS has been tracked by multiple observatories; recent Gemini South images show an increasingly prominent tail consistent with dust and gas emission as the object warms. Those observations have led many astronomers to label it a cometary body originating outside the Solar System, following physical expectations for volatile-rich interstellar objects. Loeb has publicly challenged that consensus by highlighting the object’s apparent size range and a trajectory that approaches several planetary orbits, arguing these features merit closer scrutiny.
Loeb has explicitly asked NASA to orient the Mars Reconnaissance Orbiter and Juno toward the object during its inner-system passage, suggesting they could detect small fragments or released material. He has also warned that if the object were technological and capable of deploying small probes, such probes could conceivably reach Earth and be classified as unidentified aerial phenomena (UAPs) by investigators. In interviews and blog posts he frames monitoring as low-cost insurance against missing a potentially historic discovery while acknowledging the probability of a natural origin.
Other researchers emphasize that cometary activity explains the most salient observational features so far: an extended tail, increasing dust production with solar approach, and spectral signatures that have not yet produced unambiguous anomalies. Teams working with Gemini South and other facilities continue to collect photometry and spectroscopy to refine composition models and to constrain size and mass estimates. The debate remains scientific: competing hypotheses are evaluated by what measurements can confirm or rule out.
Analysis & Implications
If 3I/ATLAS proves to be natural, it still offers a rare opportunity to study the composition and dynamics of an interstellar comet larger or brighter than previously observed examples. High-quality observations during perihelion can refine models of how interstellar small bodies survive interstellar travel and respond to stellar heating. Those data would inform theories of planetesimal formation in other systems and improve our understanding of the population and frequency of interstellar visitors.
Conversely, if the object showed signs inconsistent with natural processes — engineered structure, controlled fragmentation, or the deployment of secondary objects — the scientific and policy consequences would be profound. Verification would require extraordinary evidence and rigorous, independent confirmation from multiple instruments and teams. Any claim of artificiality would raise immediate questions about detection standards, data sharing, planetary protection protocols and the governance of follow-up observations.
Loeb’s suggested use of existing spacecraft to monitor 3I/ATLAS highlights a pragmatic step that could be taken without new launches: repurposing spacecraft instruments to capture high-resolution imaging, spectra or particle detections during the passage. Doing so would require interagency coordination, mission-team approval and an assessment of scientific return versus operational risk. The episode also underscores the value of having protocols for opportunistic observations of transient interstellar visitors.
Comparison & Data
| Object | First observed | Estimated size (reported range) | Notes |
|---|---|---|---|
| 1I/ʻOumuamua | 2017 | ~100–1,000 meters (various estimates) | Unusual shape and non-gravitational acceleration debated |
| 2I/Borisov | 2019 | ~0.5–1.0 kilometers (nucleus estimates) | Clearly cometary with volatile outgassing |
| 3I/ATLAS | Observed earlier this year | Estimates up to 28.5 miles (≈45.9 km) across (Loeb) | Gemini South reports a growing tail; size remains highly uncertain |
The numbers above summarize published ranges and reported estimates; they are not all directly comparable because size inferences depend on albedo, shape and composition assumptions. Avi Loeb has argued that, if the upper-end size estimates for 3I/ATLAS hold, its mass could far exceed that of prior interstellar visitors — a point he uses to question simple formation scenarios. Most investigators stress that mass scales with uncertain parameters and that extraordinary mass estimates require corroborating evidence from multiple methods.
Reactions & Quotes
If we are visited by a technological object like 3I/ATLAS — it could either visit us or release some mini-probes that arrive to Earth and appear as [unidentified aerial phenomena].
The Sol Foundation podcast — Avi Loeb
Loeb made this statement while arguing that the possibility, however remote, justifies focused monitoring. He framed the request as an empirical test: use existing assets to look for telltale signatures rather than dismissing the hypothesis out of hand.
There is not enough material in interstellar space, if that object is the size some estimate it to be; that would be a million times more massive than previous interstellar objects we’ve seen.
NewsNation interview — Avi Loeb
Here Loeb emphasized his skepticism of conventional formation explanations if the largest size estimates are correct, while also acknowledging that a simpler, natural explanation (a rocky or icy body with surface ice sublimation) could account for current observations.
Unconfirmed
- Whether 3I/ATLAS is an artificial or engineered object — no independent, peer-reviewed evidence currently supports that claim.
- Upper-end size estimates (up to 28.5 miles) — these figures come from preliminary interpretations and remain subject to revision.
- Any release of mini-probes that could reach Earth and appear as UAP — this scenario is speculative and has not been observed or corroborated.
- Claims that the trajectory is intentionally “fine-tuned” for planetary encounters — analyses attributing intent are unproven and require careful dynamical study.
Bottom Line
3I/ATLAS presents a high-value, time-limited observational opportunity regardless of its ultimate classification. The strongest, most likely explanation based on current data is a natural, comet-like body shedding dust and gas as it nears the Sun, but some respected scientists argue the anomaly merit closer, targeted monitoring using existing spacecraft and ground assets.
Practical next steps include coordinated observations (optical, infrared, spectroscopy, and, where possible, in-situ particle detection) and transparent data sharing among teams. The scientific method requires both openness to unexpected possibilities and rigorous standards of evidence: extraordinary claims require extraordinary confirmation, and current claims of artificiality remain unverified.
Sources
- Futurism — news outlet reporting original summary and interviews
- NewsNation — media interview covering Avi Loeb’s comments (media)
- The Sol Foundation — podcast interview cited by Avi Loeb (podcast/primary quote)
- Gemini Observatory (Gemini South) — observatory that provided imaging and observational data (observatory/official)
- NASA — Mars Reconnaissance Orbiter and Juno pages (NASA/official mission information)