RECENT scientific investigations have uncovered evidence of vast, previously unknown reservoirs of primordial water located thousands of kilometers beneath Earth’s surface. This discovery offers significant new clues for understanding the planet’s geological evolution and the origin of its life-sustaining oceans.

The key to this finding lies in bridgmanite, the dominant mineral of Earth’s mantle — the immense, semi-solid layer of hot rock between the crust and the core. By simulating the extreme conditions found 660 kilometers underground, researchers discovered that bridgmanite possesses a remarkable capacity to retain water even at blistering temperatures nearing 4,100 degrees Celsius.

Published in the journal Science, these findings reshape our understanding of how water is stored deep within the planet. They suggest that water retained from Earth’s earliest, most violent era was likely a crucial ingredient in transforming the planet from a molten inferno into a habitable world.

Professor Du Zhixue of the Guangzhou Institute of Geochemistry, who led the research, explained the process. Approximately 4.6 billion years ago, Earth was a chaotic, magma-covered sphere subjected to constant celestial impacts. In this fiery environment, liquid water could not exist on the surface. However, as this global magma ocean began to cool and crystallize, forming the first solid mantle, substantial amounts of water became chemically “locked away” within the newly forming minerals.

Bridgmanite, the first and most abundant mineral to crystallize from the magma, acted like a microscopic sponge. Its inherent water-storage capacity directly determined how much primordial water was sequestered from the cooling magma. Previous studies, based on lower temperature models, had underestimated this capacity. Using a custom-built ultra-high-pressure experimental device, Du’s team was able to replicate the intense heat of the early deep mantle. They found that bridgmanite’s water-locking ability actually increases with temperature and could be five to 100 times greater than prior estimates.

To achieve this breakthrough, the researchers employed innovative techniques. They used lasers to generate immense heat and conducted high-temperature imaging to observe water storage under realistic early-Earth conditions.

In collaboration with Professor Long Tao from the Chinese Academy of Geological Sciences, the team also utilized atom probe tomography. This method functioned like an ultra-high-resolution chemical CT scan at the nanometer scale, allowing scientists to visually confirm that water molecules were indeed trapped within the crystalline structure of bridgmanite.

According to the team's models, the volume of water retained in this early solid mantle could have been equivalent to 0.08 to 1 times the total volume of all modern oceans. This deep reservoir is far from a static stockpile. Instead, the water acts as a vital geological lubricant. By lowering the melting point and viscosity of mantle rock, it facilitates the slow, convective circulation of this hot, dense layer. This internal engine, in turn, drives the movement of tectonic plates at the surface and sustains the planet's long-term geological vitality.

Over billions of years, a portion of this deeply sequestered water has gradually migrated back toward the surface through volcanic activity and magma movement. This process is believed to have been fundamental in forming Earth’s early atmosphere and primordial oceans.

Thus, the water sealed within Earth’s deep structure during its infancy likely provided the essential catalyst for the planet’s dramatic transformation into the blue, life-bearing world we know today.

(SD-Agencies)