Lost City as cradle of life?

Hydrothermal vents of the "Lost City" produce the chemical building blocks of life

Researchers take gas samples at hydrothermal vents. The picture shows newly formed carbonate minerals and - at the top right - bacterial filaments floating in the warm currents. © University of Washington, IFE, URI-ILO, NOAA
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Was the cradle of life under water? After all, the hydrothermal vents of the oceans are considered promising candidates for this. One of these vent fields even generates hydrocarbons, molecules that are considered to be building blocks of life. An international research team reports now in "Science".

Compounds from the most diverse combinations of carbon and hydrogen are the key to almost all life. For example, simple hydrocarbon chains form cell membranes, and amino acids are nothing more than short hydrocarbon chains with additional atoms such as nitrogen, oxygen, and sulfur. "The production of hydrocarbons was the first step, otherwise the earth would have remained lifeless, " explains Giora Proskurowski, one of the two main authors of the study.

Unusual vent field from "white smokers"

Some scientists suggest that these first building blocks of life may even have come from space, brought by meteorites. Others, however, see more geological processes on earth as a source, and consider the hydrothermal vents on the seabed as one of those places. From these vents located in geologically active zones very hot, mineral-rich water from the depths of the subsoil swells into the seawater.

While the well-known black smokers in particular emit a dark broth of iron- and sulfur-containing minerals, another type of hydrothermal vents consists of almost pure carbonate rocks and appears more whitish to light gray. Scientists discovered a whole cluster of these vents in 2000 on the Mid-Atlantic Ridge, some 3, 700 kilometers east of Florida. In the Vent City named "Lost City", giant giants rise more than 50 meters above the ocean floor - higher than ever before discovered.

Extremely high hydrocarbon concentration

Most interesting, however, is what comes out of the vents of the "Lost City": Because at around 90 ° C compared to the black smokers rather moderately warm water contains an extraordinary amount of hydrocarbons. Their concentration is ten to one hundred times that previously known at Vents. They are caused by a reaction of heated seawater with the mantle rock below the surface and are unusually complex. display

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"Lost City is extraordinary because chemical reactions in the seabed produce acetate, formate, hydrogen, and alkaline liquids, " explains Deborah Kelley, a professor at the Washington University and second lead author of the study. All of these substances are key factors in the development of life and could be important sources of energy for the ancestors of today's methane-consuming bacteria.

Clearly of non-biological origin

According to the scientists, the specific isotope ratio of the hydrocarbons excludes that they originate from the atmosphere or the biosphere. "The discovery of these organic building blocks from a non-biological source is an indication in our search for the origins of life on this planet and on other planets, " said Proskurowski.

Although no Vent Vent has been found so far, such as the Lost City, Kelley is sure that there must be others of this kind. Because there are numerous places on the seabed, where the mantle rock was raised by the geological activity and thus can come into contact with seawater.

(Woods Hole Oceanograhic Institution, 01.02.2008 - NPO)