Ocean floor breathes oxygen; Superconductors leap forward; Hepatitis C meets its DIY match

Seabed minerals produce ‘dark oxygen’; High-temp wires break records; and WHO approves first hep C self-test kit in this edition of Science Notebook.

A bed of manganese nodules from deep offshore of the Cook Islands taken during a Japanese research cruise in 2000. The nodules range in size from about 2 cm to 10 cm across. | Photo Credit: USGS, James Hein

The deep sea’s dark secret: Oxygen from stone

AN international team of researchers has discovered that metallic minerals on the deep-ocean floor produce oxygen. The surprising discovery challenges the long-held assumption that only photosynthetic organisms, such as plants and algae, generate the earth’s oxygen. Now it appears that oxygen can also be produced on the sea-floor, about 4,000 m below the ocean surface where no light can penetrate, to support the oxygen-breathing (aerobic) sea life living in complete darkness. The oxygen so produced is termed “dark oxygen”.

The study was recently published in Nature Geoscience.

Andrew Sweetman of the Scottish Association for Marine Science made this discovery while sampling the seabed of the Clarion-Clipperton Zone, a mountainous submarine ridge along the sea-floor that extends nearly 7,200 km along the north-east quadrant of the Pacific Ocean.

“When we first got this data, we thought the sensors were faulty because every study ever done in the deep-sea has only seen oxygen being consumed rather than produced,” Sweetman said. “We would come home and recalibrate the sensors, but over the course of 10 years, these strange oxygen readings kept showing up. We decided to take a back-up method that worked differently to the optode sensors we were using. When both methods came back with the same result, we knew we were onto something ground-breaking and unthought-of.”

“[O]ur understanding has been that Earth’s oxygen supply began with photosynthetic organisms,” he said. “But we now know that there is oxygen produced in the deep sea, where there is no light. I think we, therefore, need to revisit questions like: Where could aerobic life have begun?”

Polymetallic nodules, natural mineral deposits that form on the ocean floor, sit at the heart of the discovery. The nodules are a mix of various minerals of sizes anywhere between tiny particles and an average potato. “The polymetallic nodules [natural mineral deposits that form on the ocean floor] that produce this oxygen contain metals like cobalt, nickel, copper, lithium, and manganese, which are all critical elements used in batteries,” said Franz Geiger of Northwestern University, Illinois, who co-authored the study. “Several large-scale mining companies now aim to extract these precious elements from the sea-floor at depths of 3,000-6,000 m below the surface. We need to rethink how to mine these materials so that we do not deplete the oxygen source for deep-sea life.”

In his previous work, Geiger had found that rust can generate electricity when combined with salt water. The researchers wondered if the deep-seabed polymetallic nodules generated enough electricity to produce oxygen by seawater electrolysis. To investigate this hypothesis, Sweetman shipped several pounds of such nodules to Geiger’s laboratory. They found that just 1.5 volts, which is what a typical AA battery generates, is enough to split seawater. Amazingly, the team recorded voltages of up to 0.95 V on the surface of single nodules. And when multiple nodules clustered together, the voltage could be much more significant, just like when batteries are connected in a series.

“It appears that we discovered a natural ‘geobattery’,” Geiger said. “These geobatteries are the basis for a possible explanation of the ocean’s dark oxygen production.”

Pulsed laser deposition, in which a laser beam ablates a material that is deposited as a film on a substrate, was used to fabricate the high-temperature superconductivity wires. | Photo Credit: University at Buffalo

Superconductors are heating up the energy race

OUR future energy needs critically depend on our ability to fabricate applications with high-temperature superconductivity (HTS) at a price-performance metric that will be on par with plain copper wires. A research team led by Amit Goyal of the University at Buffalo has claimed that its recent work has brought the world closer to that goal. This study was published in a recent issue of Nature Communications. The researchers reported that they had fabricated the world’s highest-performing HTS wire segment at a significantly more favourable price-performance metric.

Based on rare-earth barium copper oxide (REBCO), their wires achieved the highest critical current density (the amount of electrical current carried) and greatest pinning force (the ability to pin down magnetic vortices) reported to date for all magnetic fields and temperatures from 5 kelvin (−268°C) to 77 K (−196°C). These temperatures are still extremely cold but higher than near absolute zero at which traditional superconductors work. “Making the price-performance metric more favourable is needed to fully realise the numerous large-scale, envisioned applications of [high-temperature] superconductors,” Goyal said.

The following are the record values of critical current density and pinning force Goyal’s team achieved. At 4.2 K, the REBCO HTS wires carried 190 million amperes (MA)/cm² without any external magnetic field (also known as a self-field) and 90 MA/cm² with a magnetic field of 7 tesla. At the warmer temperature of 20 K, the envisioned application temperature for commercial nuclear fusion, the wires could still carry over 150 MA/cm² self-field and over 60 MA/cm² at 7 tesla.

As for pinning force, the wires showed a strong ability to hold magnetic vortices pinned or in place, with forces of about 6.4 teranewton/m³ at 4.2 K and about 4.2 teranewton/m³ at 20 K, both under a 7 tesla magnetic field. “These results demonstrate that significant performance enhancements are still possible and hence the associated reduction in cost that could potentially be realised in optimised, commercial HTS  wires,” Goyal said.

An illustration of a hepatitis C virus model. | Photo Credit: Getty Images/iStockphoto

The DIY test that could wipe out hepatitis C

IN its effort to expand access to testing and diagnosis, the WHO in July pre-qualified the first hepatitis C virus (HCV) self-test. This can help accelerate global efforts to eliminate hepatitis C. The product, called OraQuick HCV self-test, manufactured by OraSure Technologies is an extension of the pre-qualified OraQuick HCV Rapid Antibody Test that was initially pre-qualified in 2017 for professional use. The self-test version, specifically designed for laypeople, provides individuals with a single kit containing the requisite components for doing the self-test.

The WHO recommended HCV self-testing in 2021 to complement existing global HCV testing services. The recommendation was based on evidence demonstrating its ability to increase access to and uptake of services, particularly among people who may not otherwise test. “Every day 3,500 lives are lost to viral hepatitis. Of the 50 million people living with hepatitis C, only 36 per cent had been diagnosed, and 20 have received curative treatment by the end of 2022,” said Meg Doherty, WHO Director of the Department of Global HIV, Hepatitis and Sexually Transmitted Infections Programmes.