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Earth's first living beings used hydrogen gas for energy

Hydrogen, or H2, is the most abundant element in the entire universe. Scientists have long suspected that hydrogen gas was the key energy source for Earth‘s earliest lifeforms. But the question was how?

Living things need a way to convert energy sources into usable forms. For our bodies, that means breaking down food to power everything we do. For the first cells, the challenge was figuring out how to utilize hydrogen.

New insights from teams across Germany and Asia point to a surprisingly simple answer. The research suggests that alkaline hydrothermal vents could be the missing link.

Hydrothermal vents and the origin of life

Hydrothermal vents are openings in the sea floor where geothermally heated water emerges. They’re found in places where the Earth’s tectonic plates are moving apart or where volcanic activity is present.

This hot, mineral-rich water, which can reach temperatures exceeding 752°F, mixes with the cold, deep-sea water around it.

Despite the extreme conditions — immense pressure, scalding temperatures, and no light — these vents teem with diverse life forms.

Scientists are constantly intrigued by life thriving in such harsh conditions. They believe these vents could reveal how Earth’s life started.

Hydrogen gas in pushing electrons

So, how do the deep-sea creatures survive and even flourish? The research helps us understand one of the secrets to life at these vents: harvesting energy from hydrogen gas.

Think of hydrogen gas as a kind of fuel for these microorganisms. But there’s a catch. To extract energy from hydrogen, cells have to do something that seems to defy nature — they have to move electrons in an energetically “uphill” direction.

“In order to harvest energy, cells first have to push the electrons from H2 energetically uphill,” explains Max Brabender, one of the study’s authors. “That is like asking a river to flow uphill instead of downhill, so cells need engineered solutions.”

Role of iron in Earth’s origin

The secret to this uphill energy transfer? It turns out, a humble metal – iron – may have played a starring role.

At the alkaline pH of these vents, scientists discovered that iron, produced by natural processes in this environment, could split hydrogen and send those energy-carrying electrons in the right direction.

No fancy enzymes or complex cellular machinery were needed!

“Metals provide answers,” says Martina Preiner from the Max Planck Institute (MPI) . “At the onset of life, metals under ancient environmental conditions can send the electrons from H2 uphill, and we can see relicts of that primordial chemistry preserved in the biology of modern cells.” But metals alone are not enough.

“H2 needs to be produced by the environment as well,” adds co-first author Delfina Pereira from Preiner’s lab.

Insights from hydrogen gas study

“Several different theories have proposed how the environment might have pushed electrons energetically uphill…we have identified a process that could not be simpler and that works in the natural conditions of hydrothermal vents,” notes William F. Martin, lead researcher from the University of Düsseldorf.

“That hydrogen can make metallic iron out of minerals is no secret,” says Harun Tüysüz, an expert for high-tech materials at the Max-Planck-Institut für Kohlenforschung Mülheim and co-author of the study.

“Many processes in the chemical industry use H2 to make metals out of minerals during the reaction.” The surprise is that nature does this too, especially at hydrothermal vents, and that this naturally deposited iron could have played a crucial role in the origin of life.

Study significance

The beauty of this discovery lies in its simplicity. The same process found in modern microbes might have been the key that kick-started life itself billions of years ago.

It creates an image of Earth’s earliest lifeforms. These organisms didn’t rely on complex machinery. Instead, they tapped into a natural mechanism to gather the essential energy and make a crucial leap towards life.

More about hydrothermal vents and hydrogen gas

As discussed above, hydrothermal vents, the seafloor’s mysterious geysers, captivate scientists and oceanographers with their extreme conditions and unique ecosystems. These fascinating features of the deep sea offer insights into the origins of life, the limits of biological endurance, and the potential for life beyond Earth.

Definition and formation of hydrothermal vents

Hydrothermal vents are fissures on the planet’s surface from which geothermally heated water discharges. Located primarily on mid-ocean ridges, these vents form when seawater seeps through cracks in the ocean floor, heats up by the magma beneath the Earth’s crust, and then gushes back into the ocean, creating plumes of mineral-rich water that support a diverse range of life forms.

The process begins with tectonic plates diverging at mid-ocean ridges, creating new oceanic crust and allowing seawater to penetrate the Earth’s crust. As the water interacts with the hot magma, it becomes superheated, dissolving minerals and metals from the surrounding rocks.

This superheated, mineral-rich water, which can reach temperatures of up to 400°C (752°F), then rises and exits through the seafloor, cooling rapidly as it mixes with the ocean water, causing the dissolved minerals to precipitate and form chimney-like structures around the vents.

Living on hydrogen gas in extreme conditions

Hydrothermal vents are home to unique ecosystems that thrive in conditions once thought to be inhospitable to life. These ecosystems rely not on photosynthesis, which is impossible in the dark depths of the ocean, but on chemosynthesis.

Microorganisms at the base of the vent ecosystem convert the chemical energy from the vent minerals into organic compounds, serving as the primary producers and supporting a diverse community of organisms, including giant tube worms, clams, and unique species of fish and crustaceans.

Past, present, and future significance

Hydrothermal vents have significant scientific, economic, and environmental importance. They provide unique natural laboratories for studying the origins of life, as the chemosynthetic processes observed at vents are similar to those that might have occurred on the early Earth.

Additionally, hydrothermal vents are of interest for bioprospecting, as organisms adapted to extreme conditions often produce unique enzymes and compounds that can be of pharmaceutical and industrial use.

Moreover, vents play a crucial role in the geochemical cycles of the ocean, influencing the composition of seawater and the global distribution of minerals. However, they also face threats from deep-sea mining and climate change, raising concerns about the need for their conservation and sustainable management.

Challenges and opportunities

Studying hydrothermal vents poses significant technical challenges due to their deep, remote locations and the extreme conditions present. However, advances in deep-sea exploration technologies, such as remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs), are enabling more detailed and frequent studies of these fascinating systems.

The exploration of hydrothermal vents not only expands our knowledge of Earth’s processes and life in extreme environments but also enhances our understanding of the potential for life on other planetary bodies. For instance, Jupiter’s moon Europa and Saturn’s moon Enceladus, both of which have subsurface oceans, may host hydrothermal vent-like conditions, suggesting the possibility of life beyond Earth.

Implications and future study

In summary, hydrothermal vents, with their extreme conditions and unique ecosystems, continue to fascinate and challenge our understanding of life and the Earth’s processes.

As we explore these enigmatic features of the deep sea, we uncover the secrets of our own planet and open the door to discovering the potential for life in the far reaches of the solar system.

The study of hydrothermal vents represents a thrilling intersection of geology, biology, and astrobiology, offering insights and opportunities that stretch the imagination and drive forward the frontiers of science.

The study is published in Proceedings of the National Academy of Sciences.


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