They are the most controversial astronomical photos of the last two months. And to no one’s surprise, speculation as to why NASA had not published them was exaggerated. This is what the space agency has seen.
A little context. Since the ATLAS system detected a new interstellar object crossing our neighborhood, a very specific part of the scientific community has been carefully monitoring its trajectory to detect any anomalies. Especially since cosmologist Avi Loeb suggested it could be an artificial alien object.
That NASA took a month and a half to release 3I/ATLAS images taken during its approach to Mars has not helped control such speculation. But the administrative silence, caused by the US government shutdown, has come to an end. NASA is back this week with a huge amount of data under the arm.
“It’s a comet.” NASA has mobilized 12 of its spacecraft to observe the visitor from outside the solar system. And the official message is forceful, almost designed to nip any exotic speculation in the bud: “it looks like a comet and behaves like a comet, and all the evidence points to it being a comet,” said Amit Kshatriya, the agency’s highest-ranking official, in a press conference.
Of course, it is a different comet from those in the solar system, which suggests that it was born in an environment with a different chemistry than ours, perhaps around a star much older than the Sun, because it is unusually rich in nickel and, instead of expelling water, it expels carbon dioxide.
What’s new. What makes this new observation campaign special is the geometry. When 3I/ATLAS passed its closest point to the Sun in late October, Earth was on the “wrong side,” with the Sun blocking our direct view.
Taking advantage of the fact that Mars had a privileged view, NASA forced the instruments of its ships beyond their original design. The Mars Reconnaissance Orbiter captured high-resolution images from 30 million kilometers away. The MAVEN mission analyzed its ultraviolet composition and the Perseverance rover, from the Martian surface, managed to capture a faint flash of the comet.
Meanwhile, the Psyche and Lucy spacecraft, traveling to distant asteroids, managed to capture the comet against the light, revealing details of its tail and coma that would be invisible from Earth. And the SOHO and STEREO solar observatories followed suit when it was too close to the Sun for other telescopes.
What does Loeb say? The controversial Harvard astrophysicist and techno-signature hunter has published an immediate response showing his disappointment. For Loeb, the NASA press conference has been an exercise in bureaucracy to confirm the “expected and boring.” His main arguments for maintaining skepticism are:
- The striking thing about the mass: 3I/ATLAS is a million times more massive than ‘Oumuamua. Statistically, we should have seen millions of small objects before seeing one this big, unless it was intentionally “sent”, according to the cosmologist.
- The camouflage theory: Loeb argues that an interstellar probe that has traveled through the cold interstellar medium could have accumulated a layer of ice and dust on its surface. As it approaches the Sun, this layer would sublimate, making it look like a natural comet.
- The resolution of the images: The photos shown by NASA are blurry (due to the limitations of the probes), so Loeb is pinning his hopes on images taken by amateur astronomers as the comet approaches Earth.
And now what. NASA has not found any technosignatures: no radio signals, no impossible maneuvers outside of gravity, nothing that indicates intelligence on this comet.
However, the show is not over. On December 19, 2025, 3I/ATLAS will have its closest approach to Earth (about 270 million kilometers). It will be then when the James Webb space telescope and the large terrestrial observatories will be able to perform the definitive autopsy.
Image | POT
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