How Earth got its water: Meteorite reveals surprising new clues

For decades, scientists have tried to answer a simple but fundamental question – where did Earth’s water come from? Without hydrogen, the main ingredient in water, our planet wouldn’t have been able to support life.

Many believed hydrogen arrived later, hitching a ride on asteroids during Earth’s earliest years. But a recent study suggests a different story. Earth may have had everything it needed to make water right from the start.

Evidence in a rare meteorite

Researchers from the University of Oxford have found compelling evidence in a rare meteorite, an enstatite chondrite, that points to hydrogen being present when Earth was first forming – 4.55 billion years ago.

The findings challenge the long-held idea that water had to be delivered after Earth had already taken shape.

“Although water is central to planetary habitability as we know it, the mechanism by which Earth gained its substantial present-day water budget is unclear,” wrote the researchers.

“Enstatite chondrites (ECs) closely resemble terrestrial rocks across a range of isotopic compositions. Hence, ECs (or material similar to these meteorites) have been suggested as the predominant building blocks of the proto-Earth, as well as other terrestrial planets including Mars.”

Ancient clues hidden in the meteorite

The team analyzed a specific enstatite chondrite meteorite called LAR 12252. This sample was collected in Antarctica and is chemically similar to the material that originally formed our planet.

The researchers used X-Ray Absorption Near Edge Structure (XANES) spectroscopy at the Diamond Light Source in Oxfordshire. This powerful tool allowed them to study the meteorite’s elements in fine detail.

Earlier research by a French team had found some hydrogen in the meteorite, particularly in organic bits and the non-crystalline parts of chondrules – the tiny round structures inside the rock.

But there were still questions. Was this hydrogen truly native to the meteorite? Or had it come from Earth after the rock landed?

Looking beyond the expected

The Oxford scientists had a hunch. They thought hydrogen might be connected to the sulfur in the meteorite. So they aimed the synchrotron’s intense X-ray beam at the sample to search for sulfur-based compounds.

Initially, they focused on the same non-crystalline areas where hydrogen had previously been found. But then something unexpected happened.

When they looked at the fine material just outside one of these chondrules – a tiny matrix of dust – they found it packed with hydrogen sulfide. Surprisingly, this matrix held five times more hydrogen than the parts previously studied.

Even more telling, parts of the meteorite that showed visible signs of weathering or rust had little to no hydrogen at all. This strongly suggests the hydrogen sulfide in the matrix isn’t from Earth – it’s original to the meteorite.

A new origin story for Earth’s water

These findings change how we think about Earth’s early history. If the proto-Earth was built from materials like enstatite chondrites, it means our planet had enough hydrogen to produce water even before asteroids ever showed up.

Study lead author Tom Barrett, a DPhil student at the University of Oxford, said the team was incredibly excited when the analysis revealed that the sample contained hydrogen sulfide – even though it was not where they had expected.

“Because the likelihood of this hydrogen sulfide originating from terrestrial contamination is very low, this research provides vital evidence to support the theory that water on Earth is native – that it is a natural outcome of what our planet is made of,” explained Barrett.

Water formation was a natural process

Professor James Bryson, a co-author of the study, noted that a fundamental question for planetary scientists is how Earth came to look like it does today.

“We now think that the material that built our planet – which we can study using these rare meteorites – was far richer in hydrogen than we thought previously,” said Professor Bryson.

“This finding supports the idea that the formation of water on Earth was a natural process, rather than a fluke of hydrated asteroids bombarding our planet after it formed.”

The full study was published in the journal Icarus.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–