A new study published recently in Earth and Planetary Science Letters suggests that much of our planet's water comes from within, rather than arriving from space through collisions with ice-rich comets. The study also suggests that chemical reactions responsible for the creation of water might be the cause for enigmatic deep earthquakes in the continental mantle lithosphere.
According to the study, based on computer simulation of reactions in Earth's upper mantle between liquid hydrogen and quartz, Earth's water is created between 40 and 400 km (25 and 250 miles) below the surface.
"This is one way water can form on Earth,” John Tse, one of the study authors told New Scientist. “We show it’s possible to have water forming in Earth’s natural environment, rather than being of extraterrestrial origin.”
The simple reaction takes place at about 1 400 °C (2 552 °F) and pressures 20 000 times higher than atmospheric pressure as silica, or silicon dioxide, reacts with liquid hydrogen to form liquid water and silicon hydride.
The computer simulation was set up very close to the experimental conditions performed and reported by Japanese researchers in 2014. The researchers then simulated the trajectory of the reaction.
The simulation showed that the water does form within quartz but also that it can't escape and so the pressure builds up.
The pressure produced by the chemical reaction can reach as much as 200 000 atmospheres, which might lead to the possibility of induced earthquakes when the water finally escapes from the crystals.
The researchers are not alone in their suggestions as other studies have also found evidence of water being stored as far down as 1 000 km (620 miles).
“As long as the supply of hydrogen can be sustained, one can speculate that water formed from this process could be a contributor to the origin of water during Earth’s early accretion,” Tse said.
“Water formed in the mantle can reach the surface via multiple ways, for example, carried by magma in the form of volcanic activities.”
It is possible that water is still being made this way deep inside Earth today, and the same could be true of other planets.
Abstract of the paper
Quartz, as the most stable low-pressure polymorph of silica (SiO2), is widely abundant in Earth's crust and mantle, exhibiting relatively high chemical stability. Although silica is only slightly soluble in water at ambient conditions, producing silicon-based weakly acidic compounds, Shinozaki et al. (2014) have shown recently that water itself can be formed by dissolution of SiO2 in H 2
fluid under high- temperature and pressure conditions. Here, we have simulated this process via molecular-dynamics techniques based on a reactive force-field description of the SiO2/H 2
Diffusion of the H 2
fluid into the quartz crystal lattice was observed upon increasing temperature and pressure, followed by interaction of dissociated, atomic hydrogen with oxygen atoms in the SiO2 lattice, disrupting the lattice and leading to the formation of water. Interestingly, water is evolved in the subsurface region of the silica, and it remains confined there, isolated from the hydrogen fluid, which corresponds precisely to the ice-like spectroscopic patterns observed experimentally. The over-pressured water formed from quartz and H 2
is a possible trigger for nucleating enigmatic deep earthquakes in the continental mantle lithosphere.
- "Formation and properties of water from quartz and hydrogen at high pressure and temperature" – Zdenek Futera, Xue Yong, Yuanming Pan, John S. Tse, Niall J. English – Earth and Planetary Science Letters – January 2017 – DOI: 10.1016/j.epsl.2016.12.031
- "Planet Earth makes its own water from scratch deep in the mantle" – An article written by Andy Coghlan and published on January 27, 2017 in New Scientist.
Featured image credit: Shaun Whiteman (Flickr)
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