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New Research Challenges Theory on Earth’s Water Origin

Researchers from the University of Oxford have significantly altered the understanding of how water came to be on Earth, debunking the long-held belief that it primarily resulted from asteroid impacts. Their recent study indicates that the materials that constituted Earth were initially abundant in hydrogen, fundamental for water formation. This pivotal research has been made public in the journal Icarus.

The Oxford research team utilized a unique meteorite known as an enstatite chondrite, which possesses a composition that closely parallels that of early Earth, around 4.55 billion years ago. Their findings highlight a crucial hydrogen source that would be essential in the creation of water molecules.

They confirmed that the hydrogen present in these materials was intrinsic rather than a result of contamination. This discovery indicates that the primordial constituents of our planet were likely much richer in hydrogen than previously believed.

Hydrogen plays a vital role as a primary element of water. Without it, the development of conditions necessary to support life on Earth would have been impossible. Historically, the origins of hydrogen—and consequently water—have been the subject of substantial debate among scientists. A prevailing theory suggested that asteroids contributed necessary hydrogen over the first 100 million years of Earth’s existence. However, the latest findings argue that Earth possessed sufficient hydrogen from its inception, negating the need for extraterrestrial delivery.

The research team meticulously examined the elemental composition of a meteorite designated as LAR 12252, which was initially obtained from Antarctica. Employing X-Ray Absorption Near Edge Structure (XANES) spectroscopy at the Diamond Light Source synchrotron facility in Harwell, Oxfordshire, they conducted their elemental analyses.

Earlier investigations by a French research team had detected traces of hydrogen within the meteorite, found within its organic materials and the non-crystalline components of chondrules, which are small, spherical structures within the meteorite. However, this previous study did not account for all hydrogen, raising questions about its origin—whether it was native or came from contamination.

The Oxford researchers theorized that a significant portion of the hydrogen might be linked to the meteorite’s sulfur content. Through synchrotron analysis, they directed a potent X-ray beam onto the meteorite to identify sulfur-bearing compounds.

Initially, the team concentrated on the non-crystalline areas of the chondrules, where hydrogen was previously located. Unexpectedly, while analyzing the fine matrix material surrounding one of the chondrules, they stumbled upon an impressive concentration of hydrogen sulfide. Their results indicated that the hydrogen content in this matrix was five times greater than that found in the non-crystalline sections.

Conversely, regions of the meteorite exhibiting cracks and signs of terrestrial contamination contained minimal to no hydrogen, casting doubt on the idea that the detected hydrogen sulfide had an Earthly origin.

Given that the proto-Earth was composed of materials resembling enstatite chondrites, the findings suggest that by the time the planet grew large enough to be impacted by asteroids, it would have already accumulated a significant hydrogen supply sufficient to account for Earth’s current water abundance.

Tom Barrett, a DPhil student in the Department of Earth Sciences at the University of Oxford who spearheaded the study, expressed enthusiasm about the findings. “We were incredibly excited when the analysis indicated the presence of hydrogen sulfide—albeit in an unexpected location! The likelihood of this hydrogen sulfide originating from terrestrial contamination is very low, providing critical evidence that supports the idea that Earth’s water is native and an inherent result of the planet’s composition,” he stated.

Co-author Associate Professor James Bryson from the Department of Earth Sciences further noted, “A fundamental question for planetary scientists is how Earth came to resemble its current state. Our findings suggest that the building blocks of our planet were richer in hydrogen than previously assumed, reinforcing the theory that water formation on Earth was a natural outcome rather than a mere happenstance due to hydrated asteroids impacting our planet post-formation.”

* X-ray Absorption Near Edge Structure (XANES) spectroscopy is a technique used to determine the elemental composition and chemical state of a material, employing X-ray beams to induce energy absorption characteristics dependent on the type of element, its chemical state, and atomic bonding.

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