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"Abode unfathomable of life?" – Aquatic Worlds of the Milky Way

Posted on Apr 30, 2019

Alien ocean

Beautiful blue planets with infinite oceans may be orbiting many of the stars in a trillion of the Milky Way. In 2016, for example, Kepler astronomers discovered planets that are unlike anything in our solar system – a planetary system of the "water world" that orbits the star Kepler-62. This system of five planets has two worlds in the habitable zone – their surfaces completely covered by an endless global ocean, without land or mountains in sight.

Inside our own solar system, the moon of Jupiter. Europe, shelters a huge salty ocean beneath the icy surface that scientists believe to reach 100 kilometers – a depth 10 times greater than the Marianas Trench.

The rocky bottom of Europe's vast ocean, suggests Caltech's Mike Brown may be almost like a miniature Earth with tectonic plates, continents, deep trenches, and active centers of dissemination. "Think of ocean ridges on Earth," Brown writes in his blog, "with its black smokers burrowing rich, nutrient-rich waters in a seafloor that joins the life that survives with these chemicals. the same kind of rich chemical soup in the ocean of Europe, leading to the evolution of some kind of life, living from the internal energy generated within the core of Europe.If you are looking for whales from Europe – which many of my friends and I often play that we are – this is the world you want to look for them. "

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The chances that the water worlds are a common feature of the Milky Way have been heightened by new research published today in the Proceedings of the National Academy of Sciences (PNAS). Using computer simulations, Harvard University astronomer Li Zeng and his colleagues presented data showing that sub-Neptune-sized planets, that is, planets with radii of about two to four times larger than Earth, are probably aquatic worlds and not fenced gas dwarfs. by thick atmospheres as conventionally believed.

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Some of these sub-Neptunian planets, Zeng said, have oceans deep enough to exert pressures equivalent to one million times the pressure of the atmospheric surface. Under these conditions, the flowing water is compressed in high pressure ice phases such as Ice Seven or superionic ice. "These high pressure gels are essentially like silicate rocks inside the deep mantle of the Earth – they are hot and hard," he said. "These are completely different worlds compared to our own Earth."

In contrast, the Earth has an obvious surface, with water compositions ranging from 25 to 50 percent of the total mass of the planet, these objects would be completely negated. They "may or may not have a well-defined surface," Li said, and "can be fluid to the bottom – to full depth."

Could these oceanic worlds sustain life? Maybe even intelligent life? "There may be life there," says Lisa Kaltenegger, director of the Carl Sagan Institute in Cornell. "But could it be based on technology like ours? Life in these worlds would be under water, without easy access to metals, electricity, or fire for metallurgy. Maybe the inventiveness of life to reach a technological stage will surprise us. "

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Could the oceans of the alien waters ever evolve into life as we know it on Earth? "Purely oceanic worlds (without land on the surface)," Avi Loeb, president of the Harvard astronomy department writes in an e-mail to dailygalaxy.com, "are not likely to develop the diversity of life as we know it, depleted essential nutrients for life, such as phosphorus and molybdenum. "

"We usually think of having liquid water on a planet as a way to start life, since life, as we know it on Earth, is mainly composed of water and requires it to live," explains astrophysicist Natalie Hinkel, senior researcher at Southwest Research . Institute in San Antonio and co-investigator of the Nexus for Exoplanet System Science (NExSS) research network at Arizona State University. "However, a planet that is a world of water, or one that has no surface above water, does not have the important geochemical or elementary cycles that are absolutely necessary for life."

"I think it can be dangerous to think of everything in an Earth mentality," says Ramses Ramirez of the Tokyo Institute of Technology. "You may be losing other possibilities."

New research suggests that about 35 percent of all known exoplanets that are larger than Earth should be rich in water. The newly launched TESS mission will find many more of them, with the help of ground-based spectroscopic tracking. The next-generation space telescope, the James Webb Space Telescope, hopes to characterize its atmospheres with important implications for the pursuit of life in the Milky Way.

"It was a big surprise to realize that there must be so many worlds of water," Zeng said.

The Earth's oceans have become the channel of evolution, says Peter Godfrey-Smith in Other Minds. The cephalopods that inhabit the Earth's oceans – octopuses, squids and nautiluses, writes Godfrey-Smith – "are an island of mental complexity in the sea of ​​invertebrate animals," he writes, having developed on a different path from us, "an experience independent in the world. " evolution of large brains and complex behavior. "

"If we can make contact with cephalopods as sentient beings, it is not because of a shared history, not because of kinship, but because evolution has built minds doubly," says Godfrey-Smith. "This is probably the closest we'll get to meeting an intelligent alien."

The Daily Galaxy via Caltech, Arizona State University, Goldschmidt Conference, The Atlantic and Scientific American

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