Sea research – neither black nor white

Hydrothermal sources are considered biological hotspots and possibly even the origin of earthly life. They are located below the seabed, typically along the borders of the continental panels, where cracks often form through the continental drift. The sea water penetrating into the ocean floor heats up, reacts with the rock there and bubbles back into the water column. So far, so-called black and white smokers have been known: While the penetrating sea water is detached from the volcanic compound in the sea floor in the former sulfur and metal compounds, white smokers emit bright minerals like baryt. In contact with the cold ocean water, these connections are extracted and sometimes create many meters high black or white tube structures. A recently published in the journal “Earth and Planetary Science Letters” Study Now shows that there is a greater variety in hydrotherm sources than previously thought.

As early as 2001, international scientists, just 300 kilometers from the North Pole, discovered the Hydrothermal field of Polaris. It is located in the gakel back, an approximately 1800 kilometer long, Central Ocean back, which extends from northern Greenland to Siberia. Due to the occurrence of volcanic basalt rock on the sea floor and the clouding of the hydrothermal smoke flags, the scientists initially assumed that it was a system of black smokers.

To their surprise, however, they found small -scale, maximum 50 centimeters high chimney structures in rust brown on their expedition to Polaris 2016 on the seabed, over blue to yellowish, from which large amounts of hydrogen and methane flowed into the water column.

“While the reactions between rock in the sea floor and sea water take place in black smokers at 350 to 400 degrees, the temperatures in the seabed of Polaris are below 300 degrees,” explains first author Elmar Albers, who, as a geoscientist, now works at the Alfred Wegener Institute, Helmholtz Center for Polar and Sea Research. “At these temperatures, no metals are withdrawn from the rock.” Instead, the reaction between the sea water penetrating due to fault zones and the rock in the ocean floor occurs hydrogen and methane.

On the chimney structures, the researchers found whitish and light yellow microbes. In the rising flag, too, large concentrations of microorganisms were demonstrated that metabolized hydrogen. They form the basis of the food network in this inhospitable place. “There are no macrofauna larger than a few centimeters,” says Albers.

The find of albers and colleagues is of far -reaching importance: “Over 90 percent of the hydrothermal systems (in the deep sea) of ultra -long -prone back have only been discovered and interpreted due to the signals in the water column,” explains the geoscientist. “If we have now found out that Polaris is not a system of black smokers, this could also be the case with others.” This would also have an impact on the previous calculation of the material cycles in the ocean: Instead of iron and manganese, far more hydrogen and methane would then be released than previously assumed. In order to clarify this, every hydrothermic smoke flag would have to be persecuted to the sea floor and examined for its composition.

In addition to the gakel back, the ultra -long -protruding ocean back also includes a 7000 km long underwater mountain range in the Indian Ocean. It is no coincidence that the hydrothermal systems there are still largely unexplored: on the gakel back, the surface of the sea is covered with ice all year round, while strong winds often blow on the Southwest Indian back. “We are absolutely at the beginning in our research,” said Albers.

These underwater mountain ranges are a highly interesting field of research: unlike rapid -spread backs, the tectonic component predominates here. The new sea floor between the two drifting plates is therefore not generally not volcanic, but consists of diluted earth crust.

So far, very little has been known about the hydrothermal circulation on the flanks and far from the oceanic back. Because the temperature in which the processes run there is significantly lower, this activity is much more difficult to discover than that of the spectacular black smokers.

Another arctic hydrothermal field in the Lenatrog, at 81 degrees north, with the name Lucky B, could also be revealing. Albers’ research group examined it in 2023, on her last expedition. Its structures also emit very large amounts of hydrogen and methane. However, while the sea floor of Polaris is made of basalt rock, it is an earth mantle. “The serpentine signal – i.e. that the coat rock reacts with sea water in the seabed (note that is,) – is much stronger at Lucky B than in Polaris, and we are currently assuming that much more hydrogen and methane rises into the water column than with Polaris,” says Albers.

The current research results are also interesting for the search for life in space. Co-author of the Polaris study Christopher German, scientist at the Woods Hole Oceanographic Institution and NASA, developed an underwater robot to explore the northernmost known hydrothermal field. It could later be used as a prototype for the research of the Jupiter moon Europe and the Saturn moon Enceladus, where hydrothermal sources are also suspected. “Both are characterized by salt water oceans that lie under their ice shields and rocky sea floor,” explains German. And the interaction of these elements could create the basis for life.

Hydrogen and methane flocked into the water column from the chimney structures.

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