It is not an alien ship, but remains of a distant planet

When astronomers detected a third interstellar object visiting our solar system, they probably did not imagine that it would have an even greater impact than the previous two. The fault was with the first estimates of its size, which had a colossal upper limit of 20 kilometers, which led to several articles by Harvard professor Avi Loeb arguing that it could be “a possibly hostile extraterrestrial probe“. Although the latest observations disprove that it is an alien ship, they open new possibilities.

Goodbye to the alien hypothesis. The idea that 3I/ATLAS was a spacecraft was based on a number of apparent anomalies. Avi Loeb argued that its trajectory, unusually aligned with the ecliptic plane of our solar system, its enormous size and its supposed stealth approach were suspicious. It suggested that the object could be performing a maneuver to remain unnoticed while exploring our planets.

However, later observations dismantled these arguments one by one. The sharpest image of the comet, captured by the Hubble Space Telescope, was devastating for Loeb’s theory. It turned out that we were totally wrong about its size. The real core did not measure 20 km, but between 320 meters and 5.6 kilometers. The initial estimate had been misled by the bright, extensive “coma” of gas and dust surrounding the true core.

On the other hand, the behavior of the object, with an asymmetric material ejection and the formation of a dust tail, confirmed that it behaved like a classic comet, and not like a ship with artificial propulsion. But perhaps it is not just any comet, but a very, very interesting one.

A piece of exoplanet? According to a new hypothesis, presented in a study pending review3I/ATLAS could be a piece of an extrasolar planet: a “lithified clastic fragment” torn from a sedimentary basin on a distant world that has traveled through the cosmos to reach us. In other words, a rock made up of layers of hardened sediment, similar to those we find on Earth in ancient river or lake beds, but from outside the solar system.

Geoscientist Eahsanul Haque’s hypothesis is supported by several previous analyses. On the one hand, the trajectory of 3I/ATLAS suggests that it comes from the thick disk of the Milky Way, a region populated by stars much older than our Sun, up to 7 billion years old. This implies that the object formed in a planetary system with more than enough time to develop complex geological processes, including the liquid water activity necessary to create sedimentary basins. And its size is consistent with the size of large fragments that could be ejected from a planet after a high-speed impact.

But wasn’t it a comet? The presence of a comma and a tail does not contradict this idea. Water and other volatiles could have been trapped in the pores of the sedimentary rock. As it approached the Sun, the heat would have caused the sublimation of these ices, generating the observed cometary activity without the main object being a “dirty snowball.”

Its spectrum resembles that of D-type asteroids, rich in carbon and silicates2 This composition is compatible with that of terrestrial sedimentary rocks, such as shales or sandstones, which often contain clay and carbonaceous material formed in aqueous processes.

All eyes on 3I/ATLAS. The interest in this interstellar traveler has been such that space agencies have mobilized their instruments to study it. The European Space Agency (ESA) targeted its Martian orbiters, ExoMars TGO and Mars Expresstowards the comet during its closest approach to Mars. Although the enormous distance (30 million km) made observation a technical challenge, the images captured the diffuse coma that surrounds it.

It is expected that future observations, such as from the Juice probe, which will see it in a more active state after its close pass to the Sun, will reveal more data about its composition. But if 3I/ATLAS has already taught us something, it is the importance that missions such as the Comet Interceptor probe planned by ESA. Without a fixed target, it is designed precisely to wait in space for a long-term target or, with great luck, another interstellar visitor, to then turn on its engines and head towards it.

Image | THAT

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