Prepare to question everything you thought you knew about comets. A groundbreaking new study on the interstellar object 3I/ATLAS has just been released, and it’s challenging our understanding of these celestial bodies. The research, based on data captured by the Keck II telescope in Hawaii on August 24, 2025, reveals some truly baffling findings. At that time, 3I/ATLAS was positioned at 2.75 and 2.6 times the Earth-Sun distance (AU) from the Sun and Earth, respectively. But here’s where it gets controversial: the images, taken by the Keck Cosmic Web Imager (KCWI) in the wavelength range of 0.3425 to 0.55 micrometers, show an anti-tail extension pointing toward the Sun—a feature that defies conventional comet behavior, much like the earlier Hubble Space Telescope observations from July 21, 2025.
What’s even more perplexing is the chemical composition of 3I/ATLAS. Unlike any known comet, including the interstellar comet 2I/Borisov, its gas plume spectrum reveals prominent nickel emissions but no detectable iron. This anomaly is so unusual that it’s only been observed in industrially produced nickel alloys through the carbonyl chemical process, which involves the formation and decomposition of nickel tetracarbonyl (Ni(CO)4). The authors of the study boldly propose that this process occurs naturally near the nucleus of 3I/ATLAS, suggesting a high concentration of nickel in that region.
A narrow-band KCWI image focusing on nickel (Ni) and cyanide (CN) emissions—at wavelength ranges of 0.3865–0.3885 and 0.3605–0.3625 micrometers, respectively—confirms a central concentration of nickel relative to cyanide. The gas plume extends outward, with nickel reaching an exponential radius of 600 kilometers and cyanide stretching to 840 kilometers. And this is the part most people miss: the production rate of nickel relative to cyanide is not only higher than in 2I/Borisov but also orders of magnitude above the median for solar system comets.
The emission profiles of both nickel and cyanide around 3I/ATLAS are asymmetric, extending both toward and away from the Sun, providing undeniable evidence of an anti-tail. Yet, the white light image of 3I/ATLAS shows no typical cometary tail, which would normally be expected from dust scattering sunlight and being pushed by solar radiation pressure.
These findings further cement 3I/ATLAS as an outlier in comet classification. With each new piece of data, it becomes clearer that this object doesn’t fit neatly into our existing categories. Considering its seven previously documented anomalies, I maintain its ranking as 4 on the Loeb scale.
We’re eagerly awaiting the public release of images captured by the HiRISE camera on the Mars Reconnaissance Orbiter on October 2, 2025. These images, with a pixel resolution of 30 kilometers, will offer a side view of the glow around 3I/ATLAS when it passed within 30 million kilometers of Mars—three times sharper than our current best images from Keck and Hubble. Additional data will come from the Juice spacecraft in November 2025 and the Juno spacecraft in March 2026.
More high-quality data is exactly what we need to unravel the mysteries of 3I/ATLAS. Science thrives on evidence, not speculation, and this object is a perfect example of how the universe still holds surprises for us.
But here’s the question that lingers: Could 3I/ATLAS be more than just a peculiar comet? Could its anomalies hint at something entirely unfamiliar to our current understanding of interstellar objects? Share your thoughts in the comments—let’s spark a discussion that challenges the boundaries of what we know.
About the Author:
Avi Loeb, head of the Galileo Project and founding director of Harvard University’s Black Hole Initiative, is a renowned astrophysicist and bestselling author. His works, including Extraterrestrial: The First Sign of Intelligent Life Beyond Earth (2021) and Interstellar (2024), explore the frontiers of cosmic discovery. Loeb’s unique perspective continues to inspire both scientists and the public alike.
