The Problem: The non-gravitational acceleration reported by NASA requires that 3I/ATLAS must have lost at least 13-15% of its mass in gas and dust during its close pass by the Sun.

This should have created a massive, bright comet tail.

The Anomaly: New images taken on November 5 and 9 show no clear cometary tail or a massive debris cloud (some images show a faint coma, but nothing commensurate with the required mass loss).

Conclusion: If the object lost 13% of its mass without showing a debris plume, the mass loss must have been due to highly directed, invisible gas jets (like thrusters), or the mass was shed very rapidly and cleanly.

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2. Complex & Anti-Sunward Jets

The Anomaly: Images from November 8 show a complex jet structure with at least seven distinct jets, some of which are anti-tails (pointing toward the Sun).

The Debate: While anti-tails are sometimes optical illusions, Loeb argues the structure suggests the jets are coming from multiple, discrete sources (like thrusters), not a simple, uniform sublimation of ice.

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3. Unprecedented Chemistry & Color: The Anomaly: The object brightened faster than any known comet and was reported to turn bluer than the Sun itself.

Typically, comets become redder as they heat up and shed dust.7The Composition: Its gas plume shows:A nickel-to-iron ratio higher than all known comets (consistent with industrial alloys).

Only 4% water by mass (water is the primary component of most comets).

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4. Orbital Fine-Tuning

The Anomaly: The object's path is closely aligned to the flat ecliptic plane of our solar system (where the planets orbit) to within 5o, which has only a 0.2 percent chance of occurring randomly for an interstellar object.

The Planetary Flyby: Its path brought it within tens of millions of kilometers of Mars, Venus, and Jupiter, which Loeb notes is a "remarkable fine-tuning" with a cumulative likelihood of only .005 percent, if random.

(http://www.autoadmit.com/thread.php?thread_id=5796135&forum_id=2#49419599)