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Hydrothermal vent nanostructures can mimic life processes by directing ions and generating energy, aiding origin-of-life theories and blue energy technologies. A team of scientists has discovered inorganic nanostructures
Hydrothermal vent nanostructures can mimic life processes by directing ions and generating energy, aiding origin-of-life theories and blue energy technologies.
A team of scientists has discovered inorganic nanostructures surrounding deep-sea hydrothermal vents in the ocean that are remarkably similar to the molecules that make life as we know it possible. These nanostructures self-organize and act as selective ion channels that produce energy that can be used in the form of electricity. This discovery will not only impact our understanding of the origin of life, but can also be applied to the industrial harvesting of blue energy.
The research, led by Ryuhei Nakamura from the RIKEN Center for Sustainable Resource Science (CSRS) in Japan and the Earth Life Sciences Institute (ELSI) at the Tokyo Institute of Technology, was recently published. Nature Communication.
When seawater seeps into the Earth through cracks in the ocean floor, it is heated by magma, rises back to the surface, and is ejected back into the ocean through cracks called hydrothermal vents. The rising hot water contains dissolved minerals obtained during its time on Earth, and when it encounters cooler ocean water, chemical reactions remove mineral ions from the water, where they form solid structures called precipitates around the vent.
Hydrothermal vents are considered the birthplace of life on Earth because they provide the necessary conditions: they are stable, rich in minerals and contain energy sources. Much of life on Earth depends on osmotic energy created by ion gradients (difference in salt and proton concentration) between the inside and outside of living cells.
RIKEN CSRS researchers studied hydrothermal vents hosted in serpentinite because they contain mineral precipitates with a very complex layered structure consisting of metal oxides, hydroxides and carbonates.
“Unexpectedly, we discovered that osmotic energy conversion, a vital function of modern plant, animal, and microbial life, can occur abiotically in geological environments,” says Nakamura.
Researchers examined samples collected from the Shinkai Seep site, located at a depth of 5,743 m in the Mariana Trench of the Pacific Ocean. The key sample was an 84 cm long piece composed mostly of brucite. Optical microscopes and micrometer-sized X-ray scans revealed that brucite crystals are arranged in continuous columns that act as nanochannels for the source liquid.
The researchers noticed that the surface of the sediment was electrically charged, and that the size and direction of the charge (positive or negative) varied across the surface. Knowing that structured nanopores with alternating charge are hallmarks of osmotic energy conversion, they next tested whether osmotic energy conversion actually occurs naturally in inorganic deep-sea rocks.
The team used the electrode to record the current and voltage of the samples. When samples were exposed to high concentrations of potassium chloride, the conductivity was proportional to the salt concentration on the surface of the nanopores. However, at lower concentrations the conductivity was constant, not proportional, and was determined by the local electric charge of the sediment surface. This charge-gated ion transport is very similar to the voltage-gated ion channels seen in living cells such as neurons.
By testing samples with chemical gradients found in the deep ocean from which they were taken, the researchers were able to show that the nanopores act as selective ion channels. Where baking soda adheres to the surface, nanopores allow positive sodium ions to pass through. However, in nanopores with calcium bonded to the surface, only negative chloride ions pass through the pores.
“The spontaneous formation of ion channels found in deep hydrothermal vents has direct implications for the origin of life on Earth and beyond,” says Nakamura. “Specifically, our study demonstrates how osmotic energy conversion, a vital function of modern life, can occur abiotically in geological environments.”
Industrial power plants use salinity gradients between seawater and river water to produce energy through a process called blue energy harvesting. According to Nakamura, understanding how the nanopore structure spontaneously forms in hydrothermal vents could help engineers develop better synthetic methods to generate electricity through osmotic conversion.
Source: Port Altele
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