The 12 anomalies of 3I/Atlas that have made it such a curiosity.
Quote:1. Its retrograde trajectory is aligned to within 5 degrees with the ecliptic plane of the planets around the Sun, with a likelihood of 0.2% (see here).
2. During July and August as well as in early November of 2025, it displayed a sunward jet (anti-tail) that is not an optical illusion from geometric perspective, unlike familiar comets (see here).
3. Its nucleus is about a million times more massive than 1I/`Oumuamua and a thousand times more massive than 2I/Borisov, while moving faster than both, altogether with a likelihood of less than 0.1% (see here and here).
4. Its arrival time was fine-tuned to bring it within tens of millions of kilometers from Mars, Venus and Jupiter and be unobservable from Earth at perihelion, with a likelihood of 0.005% (see here).
5. Its gas plume contains much more nickel than iron (as found in industrially-produced nickel alloys) and a nickel to cyanide ratio that is orders of magnitude larger than that of all known comets, including 2I/Borisov, with a likelihood below 1% (see here).
6. Its gas plume contains only 4% water by mass, a primary constituent of familiar comets (see here).
7. It shows extreme negative polarization, unprecedented for all known comets, including 2I/Borisov, with a likelihood below 1% (see here).
8. It arrived from a direction coincident with the radio “Wow! Signal” to within 9 degrees, with a likelihood of 0.6% (see here).
9. Near perihelion, it brightened faster than any known comet and was bluer than the Sun (see here).
10. It exhibits sunward and anti-solar jets which require an unreasonably large surface area in order to absorb enough sunlight needed to sublimate enough ice to feed the mass flux of these jets (as calculated here).
11. Near perihelion it exhibits non-gravitational acceleration which requires massive evaporation of at least 13% of its mass (as calculated here), whereas preliminary images indicate that the object maintained its integrity and did not break up (as discussed here).
12. Its tightly-collimated jets maintain orientation across a million kilometers in multiple directions relative to the Sun despite its measured rotation.
So far, I have not updated my rank for 3I/ATLAS on the Loeb Scale (defined here and quantified here), since we expect a flood of new data in the coming weeks. If the measured speed, composition and mass flux of the jets are consistent with sublimation of volatiles from pockets of ice on the surface of a natural comet, I will reduce my Loeb Scale rank. On the other hand, if the speed and mass flux will be inconsistent with warming by sunlight of a natural comet, then I will raise the Loeb Scale rank to a higher value than 4. The rank will reach a value of 10 if there is evidence for new objects near Earth or Mars that are related to 3I/ATLAS
https://avi-loeb.medium.com/the-12th-ano...035318a5fd