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Context: Researchers found evidence of a massive ocean trapped within a mineral called ringwoodite, located deep within the Earth's mantle (700 km down).

Details

• The discovery of a gigantic ocean located approximately 700 kilometres below Earth's surface by researchers at Northwestern University, challenges existing theories about Earth's water sources and geological processes.

Discovery of the Subterranean Ocean

• Location and Size: The oceanic reservoir is situated about 700 kilometres beneath the Earth's crust and is estimated to be three times larger than all the planet's surface oceans combined. This immense volume of water is contained within a mineral called ringwoodite.
• Origins and Significance: The discovery of such a massive subterranean ocean raises questions about the origin of Earth's water. While previous theories suggested that water was delivered to Earth by comets, this finding supports an alternative hypothesis that water may have originated deep within the planet and gradually emerged over time.

Origin of water on Earth
Extraplanetary Sources	●Cometary Contributions: Comets, originating from the Kuiper belt and Oort cloud, are composed of dust and ice. While they contain water, the isotopic ratios of deuterium to hydrogen (D/H) in cometary water suggest that comets likely contributed less than 10% of Earth's water. ●Asteroidal Influence: Carbonaceous chondrites, a subclass of meteorites from asteroids, share isotopic similarities with Earth's ocean water. These meteorites could have delivered water to Earth during its early formation stages. ●Outer Solar System Origin: Some evidence suggests that Earth's water may have come from protoplanets originating in the outer Solar System, such as those from the asteroid belt or even bodies from further regions like the Kuiper belt and beyond.
Earth's Water Inventory	●Distribution: Earth's oceans represent only a small fraction of the planet's total mass. Most of Earth's water is contained in its oceans, with additional amounts in ice, lakes, rivers, groundwater, and atmospheric water vapour. ●Interior Reservoirs: Water is also stored within Earth's crust, mantle, and core, primarily in hydrated minerals or as trace amounts of hydrogen bonded to oxygen atoms in anhydrous minerals. The mantle alone could potentially store three times the mass of Earth's oceans.
Hypotheses for Water Origins	●Asteroidal Contributions: The delivery of water-rich asteroids during Earth's formation is a compelling hypothesis, supported by similarities in isotopic ratios between Earth's water and ancient meteorites like carbonaceous chondrites. ●Theia Impact Theory: Some hypotheses propose that a massive collision with a protoplanet named Theia led to the formation of the Moon and also brought significant amounts of water to Earth, originating from the outer Solar System.

Research Methodology

• Seismic Analysis: The research team deployed 2000 seismographs across the United States to study seismic waves generated by more than 500 earthquakes. By analysing the behaviour of these waves as they travel the Earth's interior, especially the core, scientists detected a distinct slowing down of the waves, indicating the presence of water within the rock structures.

Implications and Future Directions

• Earth's Water Cycle: This discovery challenges traditional beliefs about Earth's water cycle and offers new perspectives on the planet's geology and evolution. The presence of a massive subterranean reservoir suggests that Earth's water distribution and sustainability may be more complex than previously thought.
• Geological Processes: Understanding the dynamics of water movement within the Earth's mantle opens up new avenues for research into geological processes. Scientists aim to gather more seismic data from different regions globally to study mantle melting frequencies and gain insights into the Earth's water cycle.
• Exploration Prospects: The identification of this hidden ocean within Earth's mantle provides impetus for further exploration of our planet's interior. This knowledge could inform future studies on the distribution of water and other essential elements beneath the Earth's surface.

Conclusion

• The discovery of a vast subterranean ocean deep within Earth's mantle represents a significant advancement in our understanding of planetary geology and water sources. This finding challenges existing theories about Earth's water origins and highlights the complexity of the planet's internal processes.

Source:

NDTV

Wikipedia

PRACTICE QUESTION Q. With a growing population and uneven water distribution, how to create a globally sustainable water allocation system that balances the needs of agriculture, industry, and individual consumption, while considering ethical and equitable access for all?