Where did the Earth’s water come from? Meteorites do not melt, according to scientists

Where did the Earth's water come from?  Meteorites do not melt, according to scientists

The white dashed line in this illustration shows the boundary between the inner solar system and the outer solar system, with the asteroid belt roughly positioned between Mars and Jupiter. A bubble near the top of the image shows water molecules attached to a rocky portion, indicating the type of body that could be carrying water to Earth. Credit: Jack Cook/Woods Hole Oceanographic Institution

Water makes up 71% of the Earth’s surface, but no one knows how and when these huge amounts of water got to the Earth.

a New study Published in the journal nature Scientists are one step closer to answering this question. Led by University of Maryland assistant professor of geology Megan Newcomb, the researchers analyzed melted meteorites that have been floating in space since Solar SystemFormation 4 1/2 billion years ago. They found that these meteorites were very low water Content – In fact, they were among the driest extraterrestrial material ever measured.

These findings, which allow researchers to rule them out as the primary source of Earth’s water, could have important implications for the search for water — and life — on other planets. It also helps researchers understand the unlikely conditions that go along with making Earth a habitable planet.

“We wanted to understand how our planet got water because it’s not entirely clear,” Newcombe said. “Acquiring water and having surface oceans on a planet that is relatively small and close to the sun is a challenge.”

The team of researchers analyzed seven melted meteorites, or chondrites, that collided with Earth billions of years after they were split off from at least five planetesimals – bodies that collided to form the planets in our solar system. In a process known as melting, many of these minor planets were heated by the decay of radioactive elements in the early solar system’s history, causing them to separate into layers with a crust, mantle, and core.

Because these meteorites had only recently fallen to Earth, this experiment was the first time anyone had measured their volatiles. UMD geology graduate student Liam Peterson used a microelectronic probe to measure levels of magnesium, iron, calcium and silicon, then joined Newcomb at the Carnegie Institution for Science’s Earth and Planetary Laboratory to measure water contents with a secondary ion mass spectrometer.

“The challenge with analyzing water in ultra-dry materials is that any ground water can easily be detected on the surface of the sample or inside the measuring instrument, distorting the results,” said study co-author Connell Alexander, a scientist at the Carnegie Institution for Science. .

To reduce contamination, the researchers first baked their samples in a low-temperature vacuum oven to remove any Surface of the water. Before the samples could be analyzed in the secondary ion mass spectrometer, the samples had to be dried again.

“I had to leave the samples under a turbo pump—a really high-quality vacuum—for more than a month to draw out enough groundwater,” Newcomb said.

Some of meteor The samples came from the inner solar system, where Earth is located and where conditions are generally assumed to be warm and dry. Other rare specimens have come from the colder, icier outer regions of our planetary system. While it was generally believed that water came to Earth from the outer solar system, it has not been determined what types of bodies could carry that water through the solar system.

said Sonne Nielsen, study co-author and geologist at Woods Hole Oceanographic Institution. “Our paper shows that this is definitely not the case. Once the meteorites melt, there is no water left.”

After analyzing chondrite meteorite samples, researchers discovered that water makes up less than two million by its mass. For comparison, wetter meteorites – called group Carbon chondrite—they contain up to 20% water by weight, or 100,000 times more than the meteorite samples studied by Newcomb and co-authors.

This means that the heating and melting of planetesimals results in an almost complete loss of water, regardless of where in the solar system these planetesimals originated and how much water they started with. Newcomb and her colleagues discovered that, contrary to popular belief, not all outer solar system bodies are rich in water. This led them to conclude that the water was likely delivered to Earth by non-molten or chondrite meteorites.

Newcombe said their findings have applications beyond geology. Scientists in many disciplines – especially exoplanet researchers – are interested in the origin of Earth’s water because of its deep connections to life.

“Water is considered an ingredient for life so that it can thrive, so as we look out into the universe and find all these exoplanets, we’re starting to determine which of these planetary systems could be potential hosts for life,” Newcomb said. “In order to be able to understand these solar systems.” The other, we want to understand our systems.”

The paper, “Early-forming young planetesimals constrained the conduction of water to Earth,” was published in nature On March 15, 2023.

more information:
Megan Newcomb, The degassing of early planetesimals restricted the conduction of water to Earth, nature (2023). doi: 10.1038/s41586-023-05721-5. www.nature.com/articles/s41586-023-05721-5

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the quoteWhere did the Earth’s water come from? Unmelted Meteorites, According to Scientists (2023, March 15) Retrieved March 17, 2023 from https://phys.org/news/2023-03-earth-meteorites-scientists.html

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