Pluto can be composed of a billion comets

Maybe we're looking at Pluto the wrong way. Planet, dwarf planet: this semantic debate could be irrelevant, because in reality. . . Maybe Pluto is actually a kind of giant comet? In an article published this week in the journal Icarus scientists at the Southwest Research Institute present a new theory that Pluto could simply be the aggregation of a group of comets. Thousands of millions.

Scientists generally thought that Pluto was born in the usual way for a planet: in the old childhood of the solar system, a rocky core formed in a cloud of gas and dust, and gravity slowly increased more and more material , which leads to a small spherical ball that we now call Pluto. But more recent discoveries in the 90s of other small icy objects like Pluto in the Kuiper belt suggested another history of shared origin more unique to unravel.

"The current paradigm is that the bodies in the outer solar system were built by the accumulation of rocks and ice," says Christopher Glein, a scientist at the Southwest Research Institute and lead author of the new document. "We believe that comets are building blocks left over from the formation of larger bodies, and previously, it was suspected that Pluto could have been formed from cometary building blocks, but we did not have the data to really prove that. to take the next step in that process. "

The data in this document comes from two sources: the New Horizons mission in which scientists were able to make observations of a nitrogen-rich glacier on Pluto called Sputnik Planitia; and the chemical composition of Comet 67P / Churyumov-Gerasimenko, studied by the Rosetta spacecraft of the European Space Administration (RIP). The authors of the article found that the nitrogen content of the glacier was similar to that predicted by other models if Pluto had been formed by mixing billions of comets as 67P.

"First we used information from New Horizons," says Glein, "to estimate how much nitrogen is in Pluto and has escaped from Pluto's atmosphere," establishing a constraint that represents a goal for theoretical models. "" So, we use the abundance of Rosetta nitrogen, and we scale it to the mbad of Pluto. What was really interesting is that the two approaches give values ​​that agree well. "

This new model of" giant comet "is discordant, but so was the discovery of an atmosphere on Pluto, and it implies that it could possess an ocean But for a safe measure, the researchers also developed what they call a "solar model" that suggests that Pluto was formed from cold ice creams that contain an abundance of nitrogen similar to that of the sun. "The solar model provides much more "We can not rule out this model because we do not have a detailed understanding of how much nitrogen has escaped from Pluto's atmosphere throughout its history." New Horizons is "just a snapshot over time "and it is not known how nitrogen rates changed over the course of billions of years.

Like all peculiar new ideas, this one is Eyes of being bulletproof. According to Glein, the biggest limitation for the model is that New Horizons detected a very low abundance of carbon monoxide on Pluto, even though comets tend to carry high amounts of carbon monoxide. Much of this may have been buried under Sputnik Planitia, so New Horizons would obviously not detect on the surface, and an underground ocean could also have caused the destruction of carbon monoxide. "I find that the last hypothesis is especially intriguing, because there are other New Horizons tests that suggest the existence of such an ocean," he says.

Furthermore, although Glein believes that most scientists have received the study warmly, he does admit that some people have posed problems with the connotation of "giant comet". "I'm not saying that Pluto is a comet," he says, "but its composition could be related to a model of a large comet." Here there are many nuances that could be easily lost if this distinction is made. not explained carefully.

Ultimately, the only way to confirm or refute this new theory will be to study Pluto directly. That means going beyond an overflight mission like New Horizons, and sending an orbiter, and maybe even a lander, to Pluto. Glein votes to land at Sputnik Planitia, for obvious reasons, where we could try some of those fresh glacial ice creams and badyze them with a mbad spectrometer. It's hard to see a mission like that light up in the future, but the success of New Horizons means that the clamor to return to Pluto will only increase more and more.

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