The outer solar system has provided a surprising amount of Earth’s water

In a recent study published in SciencesA team of researchers at Imperial College London examined 18 meteorites containing the volatile element zinc to help determine their source, as it has long been assumed that volatiles on Earth, including water, derive from asteroids closer to our planet. However, their findings likely point to an entirely different origin story.

“Our data show that nearly half of Earth’s zinc deposits were delivered by materials from the outer solar system, beyond the orbit of Jupiter,” said Dr. Marc Recamber, professor in the Department of Earth Sciences and Engineering at Imperial, and co-author on the study, said in a statement. “Based on current models of the early development of the solar system, this was completely unexpected.”

Roughly 4.5 billion years ago, our solar system formed from a collapsing cloud of interstellar gas and dust, the collapse of which was presumably caused by a supernova explosion of a nearby star. As it collapsed, the cloud formed a rotating disk of material, a solar nebula. Over time, gravity and pressure in the center of the nebula eventually caused the hydrogen and helium atoms to fuse, giving birth to our sun. The remaining material in the nebula formed the planets and moons we see today, with rocky planets consisting of the inner part and much larger gaseous planets consisting of the outer parts.

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Since Earth formed in this inner part of the nebula, it has been a long-standing hypothesis that the majority of Earth’s constituent material also came from the inner part, so this latest research could help reshape our understanding of both the formation and evolution of our solar system.

“This contribution of outer solar system material has played a vital role in creating Earth’s stock of volatile chemicals,” Dr. Recamber said in a statement. “It appears that without the contribution of outer solar system material, Earth would have much less volatile matter than we know today – making it drier and possibly unable to nourish and sustain life.”

For the study, the researchers examined 18 meteorites that originated from a variety of locations across our solar system, 11 of the 18 coming from the inner solar system, and are known as non-carbonaceous meteorites. The remaining seven out of 18 come from the outer solar system and are known as carbonaceous meteorites.

The researchers discovered that while carbonaceous bodies account for only about 10 percent of the entire Earth’s mass, this same material is responsible for about 50 percent of the Earth’s zinc supply. The large amount of zinc, along with other volatiles, could also be contained in the large amount of water, the researchers say, which could provide clues about Earth’s water supply as well.

“We’ve known for a long time that some carbonaceous material was added to Earth, but our findings indicate that this material played a major role in determining our budget for volatile elements, some of which are essential for life to thrive,” said Risa Martins, who is a candidate for carbon dioxide. PhD in the Department of Earth Sciences and Engineering, and lead author of the study, he said in a statement.

For the next steps in their research, the team will examine Martian meteorites, of which there are currently five known meteorites on Earth, along with moon rocks, with the Red Planet of interest because it had liquid water billions of years ago.

“The popular theory is that the Moon formed when a massive asteroid slammed into the embryonic Earth about 4.5 billion years ago,” Dr. Recamber said in a statement. “Analysis of zinc isotopes in moon rocks will help us test this hypothesis and determine whether the impacting asteroid played a significant role in delivering volatiles, including water, to Earth.”

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