Until recently, all spectroscopic studies of 3I/ATLAS indicated a reddish color. The latest image of 3I/ATLAS from September 7, 2025 (reported by Michael Jäger and Gerald Rhemann here), suggests that the glow around it turned green.
The transition from red to green-blue colors might be associated with the steep rise in the production of cyanide (CN) as reported by the Very Large Telescope on August 25, 2025 (here). The production of both cyanide and nickel without iron was found to increase dramatically with decreasing heliocentric distance to the power of about 9 (+/-1).
This morning, the ATLAS telescope team released data dating back to March 28, 2025 (accessible here), showing that the cross section of scattered light around 3I/ATLAS grew inversely with heliocentric distance to the power of 3.9 when the object was farther than 3.3 times the Earth-Sun separation (AU). Once 3I/ATLAS got closer, the growth was moderated to a power-law index of 1.2. The ATLAS team interprets this anomalous evolution as a shift from scattering of sunlight by dust lifted from a reddened surface to the production of small, optically bright icy grains, which changed the opacity of the plume of materials shed off by 3I/ATLAS.
The Hubble Space Telescope image of 3I/ATLAS from July 21, 2025 (reported here) when 3I/ATLAS was at a heliocentric distance of 3.8 AU, shows an extension of scattered light towards the Sun and not away from it — as typically for comets. The Webb Space Telescope data from August 6, 2025 (reported here) and the SPHEREx space observatory from August 8–12, 2025 (reported here) showed that the plume of gas around 3I/ATLAS is dominated by carbon dioxide — CO2 (87% by mass) with traces of carbon monoxide — CO (9%), and water — H2O (most of the remaining 4%). Combined with the path of 3I/ATLAS being aligned with the ecliptic plane of the planets around the Sun, having a chance probability of a fifth of a percent, these facts make 3I/ATLAS interestingly anomalous relative to familiar icy rocks. 3I/ATLAS is different from the first interstellar object 1I/`Oumuamua which displayed no signs of evaporation but exhibited non-gravitational acceleration and also from the second interstellar object 2I/Borisov which behaved like a familiar comet.
Regarding Unidentified Anomalous Phenomena (UAP) closer to Earth, congresswoman Anna Paulina Luna will chair today at 10 AM EST a hearing of the Task Force on the Declassification of Federal Secrets at U.S. Congress, titled: “Restoring Public Trust Through UAP Transparency and Whistleblower Protection” (livestream video and written testimonies available here). The first recommendation to congress in the testimony of the U.S. Air Force Vetern Jeffrey Nuccetelli is: “Fund independent research and treat UAP study with the same seriousness as any other scientific field.” This is exactly the narrative of the Galileo Project under my leadership.
In an interview today on the program “Morning in America” of NewsNation (following another interview last night concerning 3I/ATLAS, available here), I was asked whether the release of new videos or eyewitness details in today’s congressional hearing is likely to restore public interest in UAP. I explained that this discussion is not a matter of public relations in a popularity contest, but instead a topic of great relevance for national security and science. Human history is full of misconceived notions. For example, the belief that the Sun revolves around the Earth was popular among humans even after the Earth revolved around the Sun 4.54 billion times! Once we all see credible evidence about the nature of UAP, we will be able to get to the bottom of it and everyone would agree on what it means. When asked whether I believe that the U.S. government is hiding information, I replied that as a scientist I respond to evidence and not to what people tell me.
Scientific evidence is our best path to new knowledge, whether in the realm of UAP or 3I/ATLAS. The simplest way to tell the difference between a dogmatist and a genuine scientist is to flood both of them with scientific-quality data. Whereas the dogmatist will shove anomalous data under the carpet of traditional thinking, an open-minded scientist will be thrilled to learn something new with an underlying sense of humility. Not only is nature more imaginative than we are, but it also does not care whether we figure it out. The insistence that everything in the sky is either icy rocks or human made technologies will not rid us of cosmic neighbors, if they exist out there.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
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