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Earth’s lower mantle trapped far more early water than previously thought
- New experiments show Earth’s lower mantle may store much more early water than previously believed, reshaping ideas about habitability.
- Bridgmanite, the mantle’s most abundant mineral, can contain hundreds to nearly two thousand parts per million of water by weight.
- Temperature, not pressure or composition, largely governs how much water bridgmanite stores as the mantle cools.
- Magma-ocean crystallization models show the lower mantle could hold five to a hundred times more water than earlier estimates.
- Early in Earth’s history, cooling magma oceans allowed bridging and crystallization to lock water into bridgmanite.
- The study used NanoSIMS and atom probe tomography to confirm water is integrated into bridgmanite’s crystal structure.
- If true, Earth’s deep-water reservoir could slowly resupply surface oceans and influence climate over geologic time.
- Results may help explain why the upper mantle is relatively dry while the transition zone holds more water today.
- The research suggests a deep-water reserve could recur in exoplanets during their magma-ocean phases, informing planetary habitability.
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