3I/ATLAS, the third-ever interstellar interloper since 1I/Oumuamua (2017) and 2I/Borisov (2019) entered the edge of the solar system Oort Cloud, around 8000 years ago. Spotted eight millenia later on July 01, 2025 by the ATLAS observatory, the exocomet quickly became a social media sensation by virtue of its anomalous characteristics.
Ahead of its perihelion on October 29, observations on 3I/ATLAS revealed enriched nickel emission which is usually attributed to industrial scale. The suspicion that the exocomet is an alien probe in disguise has not been proved for lack of consolidated evidence. Yet, there are at least 18 anomalies listed by Harvard astrophysicist Avi Loeb that questions the very nature of the interstellar object as a comet, say for instance the three symmetrical mini-jets and the sunward anti-tail, which are so unlucky for a textbook comet.
In his latest Medium blog, Avi Loeb, decodes the post-perigilion data obtained on November 16, 2025 by the Keck Cosmic Web Imager of the Keck II telescope on Mauna Kea in Hawaii:
Based on the new data, 3I/ATLAS shows a strong evolution in the Ni/Fe ratio, in proportion to distance from the Sun to the power of 1.15 ± 0.05. At heliocentric distances beyond 2.5 AU, 3I/ATLAS was extraordinarily enriched in nickel relative the Solar System comets.
Prof Loeb reminds
Earlier, pre-perihelion observations indicated that the plume of gas around 3I/ATLAS had an anomalously high nickel (Ni) to iron (Fe) ratio at large distances from the Sun
So what does the observation leads to? The Harvard astrpphysicst writes
The cyanide (CN) emission has a steeper dependence on heliocentric distance than tri-carbon (C3) and di-carbon molecules.
Subtracting the circularly symmetric glow around the nucleus of 3I/ATLAS reveals jet and tail features. Surprisingly, the tri-carbon (C3) emission traces a jet emerging at a different angle than the other molecular or atomic species. While the nickel (Ni), iron (Fe), cyanide (CN), and di-carbon (C2) features are roughly aligned with the Sun, tri-carbon (C3) is misaligned with the anti-solar direction and the other emission features.
See Also: 3I/ATLAS: Avi Loeb Decodes Exocomet’s Hubble Images Captured During Its Rare Full Moon Phase
Cover: Avi Loeb & W.B. Hoogendam et al.