Life may go deeper than we thought, according to Dutch scientists from the University of Utrecht. Perhaps there is an entire biosphere under our feet that is almost impossible to reach. They examined samples from a mud volcano at the bottom of the Pacific Ocean and found traces of microorganisms that may have lived several kilometers below the seabed. The preliminary publication can be seen on the Proceedings of the National Academy of Sciences website.
Living things are able to endure a variety of conditions. Recently we told, for example, that tardigrades endure complete drying out for a long time, as well as flights into open space, severe radiation and temperatures down to -217 degrees Celsius. Roundworms have also been reported that live three and a half kilometers underground. New research suggests that life may lie at greater depths.
Oliver Plumper's team analyzed 46 samples taken from the South Chamorro mud volcano, which is located near the deepest part of ocean waters on our planet - the Mariana Trench in the Pacific Ocean, where one tectonic plate crawls over another. Due to high temperatures and mechanical stress in the zone called the subduction zone, a mineral is formed - serpentine (serpentine), which erupts from time to time, although due to the pressure of a huge amount of water from above it looks rather like the creeping of mineral masses to the surface bottom.
Mud volcano South Chamorro Izu-Bonin-Mariana subduction system. Plümper et al
Using the methods of mass spectrometry (ToF-SIMS) and Raman spectroscopy, scientists have established that the organic matter of the samples consists of a mixture of aliphatic and aromatic compounds, and also contains different functional groups, including amides. Such compounds can be a waste product of living organisms. If this is true, then such organisms are chemolithoautotrophs, that is, prokaryotes that use inorganic compounds (most likely iron compounds) as a source of carbon and as an energy source.
It is known that prokaryotes live at the very bottom of the Mariana Trench, and its depth is about eleven kilometers; signs of their life were also found at a depth of about twenty meters below its bottom. In order to assess the likelihood of the existence of life even deeper, scientists built a model, the upper boundaries in which were a temperature of 122 degrees Celsius and a pressure in the gigapascal range (the limiting known conditions for the survival of bacteria), and, taking into account all known geological factors, calculated the maximum depth, on which local organisms could survive. It turned out that serpentine rocks at depths of up to ten kilometers under the ocean floor are quite suitable for this, falling into the proper temperature window.
Model of the biosphere of the subduction zone - structure (top left) and evolution (top right). Bottom shows the maximum depths where life is possible (left) and the effect of heat flows at a depth of 12 km under the ocean floor (right). Plümper et al
There is a possibility that the discovered organic molecules are not a product of the vital activity of bacteria, but arose on their own, as it happened, according to a number of hypotheses, during the origin of life on the planet. However, if the assumption is correct, and such deep forms do exist, then they can retain more ancient signs in comparison with the rest of the organisms of the planet, easily surviving, for example, such stages as a lunar cataclysm - a heavy meteorite bombardment that occurred from 4.1 to 3.8 billion years ago. In addition, scientists believe that the eruption of mud volcanoes containing such microorganisms could have a significant impact on the geochemical component of nature throughout the history of the existence of life on Earth.
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Anna Kaznadze