Researchers, led by Ryuhei Nakamura at the RIKEN Center for Sustainable Resource Science (CSRS) in Japan and The Earth-Life Science Institute (ELSI) of the Tokyo Institute of Technology, have made a groundbreaking discovery. They have found inorganic nanostructures surrounding deep-ocean hydrothermal vents that bear a remarkable resemblance to the molecules essential for life as we know it. These self-organized nanostructures serve as selective ion channels, generating energy that can be converted into electricity.
These findings not only revolutionize our understanding of the origins of life but also hold great potential for industrial blue-energy harvesting.
When seawater seeps deep into the Earth through fissures in the ocean floor, it undergoes heating by magma, rises back to the surface, and is released into the ocean through hydrothermal vents. The heated water carries dissolved minerals acquired during its journey deep within the Earth. Upon meeting the cool ocean water, chemical reactions occur, causing mineral ions to form solid structures known as precipitates around the vent.
Hydrothermal vents, those enigmatic structures hidden deep beneath the ocean’s surface, may hold the key to the origins of life on Earth. These vents provide the perfect conditions for life to thrive—stability, mineral richness, and abundant energy sources.
The RIKEN CSRS researchers have delved into the mysterious world of serpentinite-hosted hydrothermal vents, where mineral precipitates boast a remarkably intricate layered structure formed from metal oxides, hydroxides, and carbonates.
Their groundbreaking discovery has unveiled the possibility of natural osmotic energy conversion in a geological environment. This process, vital for the existence of modern plants, animals, and microbial life, was thought to be exclusive to living organisms until now.
Venturing deep into the Pacific Ocean’s Mariana Trench, the researchers collected samples from the Shinkai Seep Field, situated at an astonishing depth of 5743 meters. The key sample—a striking 84-centimeter piece predominantly composed of brucite—revealed mesmerizing insights under optical microscopes and micrometer-sized X-ray beam scans.
The brucite crystals were arranged in continuous columns, forming nano-channels that facilitated the flow of vent fluid. What’s more, the surface of the precipitate exhibited varying electrical charges, a hallmark of osmotic energy conversion in structured nanopores.
This remarkable revelation challenges our understanding of natural processes and opens new frontiers in the study of deep-sea geological environments. The implications of this discovery are nothing short of extraordinary, and the researchers are on the brink of unraveling the secrets hidden within the Earth’s ancient geological formations.
The team utilized an electrode to meticulously capture the current-voltage of the samples. Upon exposure to high concentrations of potassium chloride, the conductance exhibited a direct correlation with the salt concentration at the surface of the nanopores.
However, at lower concentrations, the conductance remained constant, indicating that it was governed by the local electrical charge of the precipitate’s surface. This intriguing charge-based ion transport bears a striking resemblance to the voltage-gated ion channels found in living cells such as neurons.
Through rigorous testing with chemical gradients resembling those found in the deep ocean, the researchers compellingly demonstrated that the nanopores function as highly selective ion channels. In regions where carbonate was adhered to the surface, the nanopores facilitated the passage of positive sodium ions. Conversely, at nanopores with calcium adhesion, only negative chloride ions were permitted to traverse.
“The spontaneous formation of ion channels discovered in deep-sea hydrothermal vents has direct implications for the origin of life on Earth and beyond,” says Nakamura. “In particular, our study shows how osmotic energy conversion, a vital function in modern life, can occur abiotically in a geological environment.”
Industrial power plants harness the salinity gradients between seawater and river water to generate energy, a revolutionary process known as blue-energy harvesting. Nakamura highlights the potential to revolutionize energy generation by delving into the spontaneous generation of nanopore structures in hydrothermal vents. This understanding could pave the way for engineers to develop superior synthetic methods for converting osmotic energy into electrical power.
Journal reference:
- Hye-Eun Lee, Tomoyo Okumura, Hideshi Ooka, Kiyohiro Adachi, Takaaki Hikima, Kunio Hirata, Yoshiaki Kawano, Hiroaki Matsuura, Masaki Yamamoto, Masahiro Yamamoto, Akira Yamaguchi, Ji-Eun Lee, Hiroya Takahashi, Ki Tae Nam, Yasuhiko Ohara, Daisuke Hashizume, Shawn Erin McGlynn & Ryuhei Nakamura. Osmotic energy conversion in serpentinite-hosted deep-sea hydrothermal vents. Nature Communications, 2024; DOI: 10.1038/s41467-024-52332-3