THE frequent earthquakes that occur in the area of Yellowstone volcano caldera in Wyoming (United States) allow the fluids circulating underground to come into contact with new rocks. Chemical reactions thus occur whose effect is unexpected: the underground microbial ecosystems they transform, with the proliferation of some species and the reduction of others. The discovery, published in the journal PNAS Nexus, was made by American researchers at the University of Montana and has a certain relevance in the study of the origin of life on Earth and in the search for extraterrestrial life forms.
The effects of earthquakes in Yellowstone
In active volcanic areas such as Yellowstone, earthquakes are frequent and fractures originate underground thus opening new routes to underground fluids which circulate under the caldera and are responsible for phenomena such as geysers. In their new paths, the fluids encounter other types of rocks. By interacting with them, they are enriched with dissolved minerals different from the previous ones, thus changing chemical composition. The chemical reactions that occur when water comes into contact with fractured rocks provide theenergy necessary for the survival of microbes that live deep underground. To understand how earthquakes affect microbial ecosystems, the researchers collected water samples from a well almost 100 m deep in Yellowstone National Park. Samples were taken five times over the course of the year 2021 and revealed that concentrations of hydrogen, sulfide and dissolved organic carbon in the fluids significantly increased after small earthquakes. These represent an important source of energy for many microbes, so the change in chemical composition was accompanied by a increase in microbes in the water. The researchers observed that the types of microbes present also changed after the seismic events: this means that these ecosystems are dynamic and not static as previously thought. The processes observed in Yellowstone could also occur in other areas of the planet.
The implications of the discovery for microbial life on other planets
The chemical reactions triggered by earthquakes could help explain how microbes are able to survive in such deep, isolated environments. Studying these environments can provide clues to the origins of life on Earth. In fact, it is believed that the first microorganisms, traces of which date back to approximately 3.8 billion years agohave developed first deep into the crust terrestrial precisely thanks to energy sources such as hydrogen and subsequently moved to the surface. The fact that gases such as hydrogen favor life is demonstrated by hydrothermal vents present at the oceanic ridges, particular structures from which water comes out heated by the underlying magma and where there is an abundance primordial microbial communities. The study on Yellowstone microorganisms also has implications in search for microbial life on other planets: the same mechanisms could in fact occur on rocky extraterrestrial bodies within which there is water.
