Natural Spa in Central Japan Found To Contain Lithospheric Water; What Does It Say About the Origin of Earth's Universal Solvent?

The essence of water being an important compound has been documented based on both historical and prehistoric evidence. It has long been thought that water on Earth originated from meteorites or asteroids during the early years of our planet. A new study, however, made the researchers consider the possibility that water could come from tectonic plates and seafloor sediments.

Where Did Water Originally Come From?

The Earth has been rich in water for a few billion years. However, scientists are still puzzled about where all this liquid comes from. Most experts believe that water was brought here by comets or asteroids, but that theory falls short in explaining how the Earth's surface was filled with so much water.

This idea was recently reinforced after samples of asteroid Bennu were returned to Earth by NASA's OSIRIS-Rex spacecraft in September. Preliminary investigation of the samples indicated the presence of water and other organic materials.

Non-Meteoric Water Discovery

Most natural spa water comes from atmospheric precipitation, like rain and snow. Such sources are known as meteoric water. In a recent study, experts from the University of Tsukuba have made an important discovery regarding the origins of natural spa waters in central Japan.

By investigating the stable isotope composition of hydrogen and oxygen in water molecules, the research team identified distinct characteristics which indicated the presence of long-trapped lithospheric water. The results of their findings were published in a paper entitled "Isotopic evolutionary track of water due to interaction with rocks and its use for tracing water cycle through the lithosphere."

The isotopic evolution of this water was traced through complex numerical modeling where they compared different types of water, such as those found deep beneath the seafloor. It was revealed that this water share a common evolutionary trajectory with water found in volcano steam from plate subduction zones, coastal oil field brines, and submarine mud volcanoes. Based on this modeling, it was suggested that this water has been trapped within the lithosphere for almost 1.5 to 5 million years.

Additionally, the researchers also developed a new method for reconstructing the original isotopic composition of lithospheric water. This was done by eliminating the effects of meteoric water contamination from the isotopic data obtained from natural spa waters. This approach enabled them to calculate the isotopic composition of lithospheric waters at the depths of different spa sites which were then compared with those reconstructed from natural spa waters.

Based on the geographical distribution of spa water, it was classified into groups: those consistent with the subduction of the Philippine Sea Plate or the Pacific Plate and those that show minimal isotopic evolution and do not align with either plate. From this classification, three primary sources were identified for this ancient water: the Pacific Plate, the Philippine Sea Plate, and ancient seafloor sediments such as those from Niigata and southwest Gunma regions.

The findings from this study do not only reveal the complex 3D structure and evolution of ultra-deep water circulation, but they also provide keys for understanding the role of water in seismic and volcanic activities. It can pave the way for advanced methods of predicting earthquakes and volcanic eruptions.