Earth’s early days are getting a fresh look. For a long time, scientists thought the planet was dry at its core. However, new research hints that it might have formed with a huge internal water reservoir buried deep in the lower mantle. This hidden water could still be affecting geological processes today.
A recent study in Science shows that a common mineral found deep within Earth, called bridgmanite, can store much more water than previously thought. This suggests that the biggest body of water on our planet might not be the Pacific Ocean, but rather an unseen reservoir more than 1,000 miles below our feet.
Researchers from the Carnegie Institution for Science, led by Wenhua Lu, conducted high-pressure and high-temperature experiments. They tried to mimic the conditions inside early Earth using a laser-heated diamond anvil cell. They reached extreme temperatures and pressures, creating conditions similar to those during the planet’s formation. Their findings indicate that bridgmanite absorbs more water as temperatures rise, meaning a significant amount of water may have remained trapped inside the mantle rather than escaping to the surface.
This insight challenges past models that underestimated the water content in Earth’s interior during its formative years. The researchers believe that the deep mantle could hold water volumes equal to several oceans, but in a different form—hydrogen atoms locked within minerals. This concept introduces a “hidden ocean” within solid rock.
The potential impact of this discovery is enormous. It could change how we understand the global water cycle, which has mostly focused on surface and atmospheric water. This deep reservoir might explain the chemical traits seen in volcanic activity, particularly in regions like Hawaii and Iceland, where magma shows signs that suggest ancient materials.
Experts suggest that this reinforces the idea that Earth’s water isn’t just from external sources like comets or asteroids that bombarded our planet long ago. Instead, it points toward a “wet accretion” process, where water was already part of Earth’s building blocks.
This understanding matters beyond just our planet. If other rocky planets also formed with internal water, they could have hidden reservoirs, even if their surfaces seem dry. This could reshape how scientists search for exoplanets that could support life—steering attention beyond just surface water.
Having a hydrated mantle would also influence how planets evolve. Internal water affects plate tectonics and volcanic chemistry and keeps Earth stable over time. Seismic waves and geochemical data hint at this deep water, suggesting that our understanding of Earth’s inner workings is still evolving.
If further research continues to confirm these findings, it may reshape our views on how planets cool, how magnetic fields behave, and how long-term climate is regulated. Scientists are eager to dive deeper into this topic, and as techniques improve, we can expect to learn more about the secrets of our planet’s interior.
