Earth’s Early Rocks May Have Produced Vast Water Supplies
Lab experiments indicate that hot, hydrogen-rich conditions could have generated water directly from rock, without relying only on icy objects from distant regions.
Key points
- Researchers at The University of New Mexico tested rock reactions under conditions resembling early Earth.
- Heating rock in hydrogen turned almost 80% of its iron oxide into metallic iron and released water vapor.
- Helium, used as a comparison, produced no such reaction, pointing to hydrogen as the key ingredient.
- Extrapolation suggests the process could have produced hundreds of oceans' worth of water.
- The authors say more research is needed to measure its share of Earth's present water.
A new study suggests that Earth may have produced much of its own water during its fiery formation. According to a report by ScienceDaily, researchers at The University of New Mexico found that rock and hydrogen can react at extreme heat to create water. Their calculations indicate the process could have generated hundreds of oceans’ worth of water.
The work was headed by graduate student Susmita Garai, who carried out the experiments at the core of the project. Zachary Sharp, who heads the Earth and Planetary Sciences group, and Peter Olson also contributed. The team recreated some of the harsh conditions that existed while Earth was forming.
How the water may have formed
For decades, scientists have debated where Earth’s water came from. A leading theory holds that icy material from the colder outer solar system was carried inward and added water to the young planet. Researchers have had difficulty showing that enough of this material could have arrived from so far away.
The new work proposes a different route. Water may have formed directly from the rocky material that built Earth, reacting with the gas around it. As small rock pieces gathered into a larger body, they could have fallen through a thick, hydrogen-heavy atmosphere. The researchers suggest that hydrogen in that gas reacted with iron oxide in the rock, turning it into metallic iron and releasing water vapor.
What the experiments showed
The team heated samples of silicate rock to between 1,200 and 1,400 degrees Celsius. They ran tests with flowing hydrogen and repeated them with helium for comparison. Each run lasted from 15 minutes to three hours.
When the rock was heated in hydrogen, almost 80% of its iron oxide became metallic iron, and water vapor was produced. No comparable reaction appeared with helium. This difference suggested that hydrogen was essential to making the water.
- The reaction proceeded faster and more fully than the scientists had expected.
- Extending the results to early Earth conditions pointed to very large volumes of water.
Sharp said the team had hoped to see iron and water form, but had no clear way to know how quickly or how much. He described the scale of the findings as surprising.
Implications for other planets
Sharp suggested that nearly every planet of Earth’s size may hold water thanks to this mechanism. Should rocky worlds orbiting other suns form in comparably scorching, hydrogen-laden air, they could likewise yield significant water as material accumulates. That would imply water does not hinge on icy objects arriving from far-off regions of a planetary system.
The study also connects to pebble accretion, the process by which small rock fragments join to form planets. Sharp noted that the idea is fairly new, having been discussed for about the last decade. He said it appears to resolve several problems in current planet formation models.
Open questions
The experiments show that rock can make water under conditions resembling early Earth. They do not establish how much of today’s water came from this process. Scientists will need further research to compare its contribution with water delivered by comets, meteorites and other sources.
Frequently asked questions
Did Earth make its own water?
According to the study, reactions between hydrogen and iron-bearing rock during Earthu0026#039;s formation could have produced water. The researchers say this does not show how much of todayu0026#039;s water came from this process.
Who led the University of New Mexico study?
The study was led by graduate student Susmita Garai. Zachary Sharp and Peter Olson also took part in the research.
Could other planets also have water?
Sharp suggested that nearly every Earth-sized planet may hold water through this mechanism. He added that other Earth-sized bodies circling other stars might also have water and possibly life.
Sources
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