Earth’s water was born within: Scientists debunk cosmic delivery theory

April 18,TG盗号软件企业定制 2025  10:35

British researchers from Oxford University have rewritten the story of how water appeared on our planet. For decades, the prevailing theory held that Earth’s oceans formed thanks to asteroids delivering water from space. A new study, published in Icarus, challenges this idea, revealing that water is Earth’s native gift, emerging from its own depths. This discovery reshapes our understanding of life’s origins and fuels hope for finding water on other worlds.

Farewell to the Asteroid Theory

The idea of “wet” asteroids dominated scientific thought for years. Researchers believed that 4.5 billion years ago, during a meteorite bombardment of the young Earth, chondrites—water-rich stony asteroids—delivered water as ice or minerals. But the Oxford team cast doubt on this by studying an Antarctic meteorite, LAR 12252, using XANES synchrotron spectroscopy.

Their analysis uncovered pristine hydrogen sulfide compounds in the meteorite—molecules that break down under heat or impact. Their presence proves the meteorite never underwent processes that could have released water to Earth. “Asteroids weren’t water’s couriers,” concludes co-author James Bryson.

Water from Earth’s Core

If not from space, where did the oceans come from? The answer lies within Earth itself. As the planet formed, hydrogen trapped in mantle minerals bonded with oxygen to create water. New models show there was five times more hydrogen than previously thought—enough to fill the oceans without cosmic help.

“Earth crafted its own water. It’s not a gift from the stars but a byproduct of planet formation,” Bryson emphasizes. This likely began in the planet’s first million years, as magma oceans and volcanism released vapor that condensed into liquid.

Why This Changes Everything

The finding upends not just Earth’s history but our broader grasp of life in the cosmos:

• Life’s Origins: Water is the bedrock of biology. If it emerged from Earth’s depths, life could have taken root in stable conditions far earlier than imagined.
• Water in Space: If planets generate their own water, the odds of finding it on Mars, Europa, or exoplanets soar. This is pivotal for NASA and ESA missions targeting “habitable zones.”
• Climate and Geology: Internal water shaped plate tectonics and the atmosphere, making Earth unique.

Up to 70% of ocean water may have come from the mantle, with asteroids contributing only a fraction. This forces a reevaluation of meteorite data, like samples from Ryugu studied by the Hayabusa-2 probe, once thought to be key water carriers.

How They Cracked the Case

The Antarctic meteorite LAR 12252 was a perfect specimen, its composition preserved by the cold. XANES synchrotron analysis probed its molecules at the atomic level, revealing their “cosmic” nature. Comparing this with models of Earth’s formation confirmed the mantle’s hydrogen as the primary source. It’s the first time a meteorite’s chemistry so clearly debunked the old theory.

What’s Next?

Researchers plan to examine more meteorites and lunar samples to refine the role of hydrogen in planet formation. Missions like NASA’s Perseverance rover and the Europa Clipper will hunt for signs of “internal” water elsewhere. This could prove water is a standard feature of rocky planets, not a rarity.

Earth was born with water in its heart, and asteroids had little to do with it. Oxford’s discovery isn’t just a scientific leap—it’s a new chapter in our planet’s story. From oceans to life, it all began within, not from the stars. As we search for water in the cosmos, Earth reminds us: sometimes the answers are closer than we think.