Where did Earth's water come from? New research challenges asteroid theory

Scientists at the University of Oxford have provided new insights into the origin of Earth’s life-sustaining water, challenging the widely held belief that water was delivered to Earth by asteroids. According to their latest study, the hydrogen necessary to form water was already present on Earth from the very beginning of the planet’s formation, making the development of liquid water an inevitable consequence of Earth's early conditions.

The research, published in the journal Icarus, analyzed the meteorite LAR 12252, which was found in Antarctica. LAR 12252 is a rare type of meteorite called an ‘enstatite chondrite,’ known for its composition similar to the early Earth. The study utilized a cutting-edge technique called X-Ray Absorption Near Edge Structure (XANES) spectroscopy, which uses powerful X-rays to identify the chemical elements in the meteorite.

Co-author Tom Barrett, a PhD student at the University of Oxford, explained that the study reveals that the material which formed Earth likely contained enough hydrogen in the form of hydrogen sulphide, a compound that can lead to the formation of water when combined with oxygen.

The study’s breakthrough came when the researchers discovered that the chondrules (spherical structures in the meteorite) were particularly rich in hydrogen sulphide. This finding is significant because hydrogen sulphide is a key indicator of hydrogen, which is necessary for water formation. The researchers noted that parts of the meteorite that were contaminated with Earth-based materials showed no signs of hydrogen sulphide, while areas of the rock that were less contaminated showed a rich presence of the compound, supporting the idea that the hydrogen was part of the original material and not a result of contamination.

Dr. Bryson, co-author and associate professor of mineralogy at Oxford, emphasized that the study suggests the material that formed Earth contained sufficient hydrogen to explain the water present on Earth today. While it’s possible that some water may have been delivered by asteroid impacts, the findings suggest that the majority of Earth’s water, particularly in the planet’s interior, was incorporated into the planet during its formation.

This discovery also brings fresh perspectives to the broader question of whether life can develop on other planets. With water being one of the key ingredients for life, scientists can now consider the possibility that planets with similar conditions to Earth may also have the ingredients for liquid water right from the start.

Although this study provides a compelling new explanation for Earth’s water, many questions remain unanswered. Researchers are still uncertain about the exact process through which hydrogen and other necessary materials were incorporated into the planet. Dr. Barrett and Dr. Bryson are hopeful that their findings will inspire further investigations into the early conditions of Earth and other planets, with the goal of better understanding how water—and life—can form in different environments.

While this research doesn’t rule out the role of asteroids in delivering some of Earth’s water, it highlights that a significant portion of the planet’s water was already present from its inception. This discovery opens new avenues for the study of water’s role in the formation of life on Earth and beyond.