Molten meteorites do not contain water

Earth is the only planet in our solar system that is covered with rivers, seas, and oceans. But where does all this water come from? A new study indicates that it could not have come from molten meteorites.

Earth is a wet planet in a dry part of our solar system. When was all this water delivered, and from what source? Researchers have been hoping to answer these questions for some time now. There is a popular theory that we owe the water to the impact of meteorites.

But US geoscientist Megan Newcomb, of the University of Maryland, disagrees. She and her colleagues studied the concentrations of water in molten meteorites that have roamed space since the formation of the solar system. they write in it Scientific journal nature Melting space rocks evaporated almost all the water, so these meteorites couldn’t fill our oceans.

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(a) Chondrites

Meteorites can be roughly divided into two groups: chondrites and chondrites. Chondrites are fragments formed in the gases of our early solar system. It often stays small and never gets so hot that it melts.

Achondrites are rocks that collapsed from large asteroids. These asteroids have undergone a melting process. Then it heats up due to the collisions. But also by radioactive elements with short half-lives, which decay after a while and a lot of heat is released in the process,” says Inge Loes ten Kate, an astrobiologist at Utrecht University and the University of Amsterdam. This gives asteroids a core, mantle and crust, just like the earth.

Both groups of meteorites may be within our solar system, where it is generally warm and dry, and in the outer part, where it is cold and wet. The chondrites and chondrites at the edge of our solar system have long been thought to contain plenty of water, even when it comes from molten asteroids.

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Newcombe and her team studied these chondrites to see if they actually contained that much water or if it was lost during the melting process. To that end, they examined seven chondrites discovered in the past 10 years. Since these meteorites had only hit Earth in recent years, this was the first time ever that they were able to measure meteorite volatiles.

Dry bones

During the research, it became clear that chondrites have a low, “extraterrestrial” water content. This was two million less than their weight. “They discovered this by looking at hydrogen molecules in minerals that formed billions of years ago during the cooling of magma (magma, ed.),” says Professor Wim van Westrenen of the Free University of Amsterdam.

Before the asteroids melted, there was plenty of water; Only 99.9 percent of it evaporates during the smelting process. Because most asteroids do not have an atmosphere, water vapor has disappeared into space.

A lot of rock from the outer edge of the solar system melted at once, and according to Newcomb, it couldn’t have been caused by water on our planet.

remains a mystery

so what? American researchers suggest two options. One is that the water comes from meteorites no more than 12 miles in diameter. They would have been too small to generate enough radiant heat to melt, so they kept a large portion of the water with them. The second possibility is that the asteroids from which the meteorites came were formed only 1.5 million years after the formation of the solar system. Most of the radioactivity had already died away by then, so not enough heat was released to cause the melting process.

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“This result tells us that we should be careful to assume that all meteorites from the outer solar system were full of water at the time of impact, because if a large part of them had melted, they would have run out of water,” concludes Ten Kate. “With this new insight, we can improve existing models about water access.” So the question remains how water ended up on our planet. But how it in no way got there is now made clear.

sources: natureAnd University of Maryland via EurekAlert!Watch 8/2021

photo: ukt2/Pixabay

Text: Kylo Timmerhuis

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