It is becoming more and more appreciated that a major part of the biologic activity is not going on at the ground surface, but is hidden underneath the soil down to depths of several kilometres in an environment coined the “deep biosphere”. Studies of life-forms in this energy-poor system have implications for the origin of life on our planet and for how life may have evolved on other planets, where hostile conditions may have inhibited colonization of the surface environment. The knowledge about ancient life in this environment deep under our feet is extremely scarce.
In numerous cracks down to depths of 1700 meter that have been partly sealed by crystals grown in them, an international team of researchers led by Dr. Henrik Drake from Linnaeus University, Sweden, has traced fundamental ancient microbial processes, including production and consumption of the greenhouse gas methane. The multi-disciplinary approach included micro-scale measurement of stable isotopes coupled with geochronology within minerals formed in response to microbial activity at several Swedish granitic rock sites. This is the most extensive study on ancient microbial activity in the continental crust yet and the findings suggest that microbial methane formation and consumption are widespread in the bedrock.
It is becoming more and more appreciated that a major part of the biologic activity is not going on at the ground surface, but is hidden underneath the soil down to depths of several kilometres in an environment coined the “deep biosphere”. Studies of life-forms in this energy-poor system have implications for the origin of life on our planet and for how life may have evolved on other planets, where hostile conditions may have inhibited colonization of the surface environment. The knowledge about ancient life in this environment deep under our feet is extremely scarce.
In numerous cracks down to depths of 1700 meter that have been partly sealed by crystals grown in them, an international team of researchers led by Dr. Henrik Drake from Linnaeus University, Sweden, has traced fundamental ancient microbial processes, including production and consumption of the greenhouse gas methane. The multi-disciplinary approach included micro-scale measurement of stable isotopes coupled with geochronology within minerals formed in response to microbial activity at several Swedish granitic rock sites. This is the most extensive study on ancient microbial activity in the continental crust yet and the findings suggest that microbial methane formation and consumption are widespread in the bedrock.
Henrik Drake explains how they tapped the stable isotope archive of minerals to decipher ancient microbial processes:
-It is well known from other environments that methane formation and consumption result in diagnostic isotope ratios in carbonate minerals formed in association with microbial processes. The micro-analyses within calcite crystals showed an extreme range in carbon-isotope compositions, which can only be explained by microbial methane formation and consumption.
Read more at Linnaeus University
Photo: Calcite crystals precipitated in response to microbial activity. Tweezers shown for scale. Size of crystals ~5 mm (height). Photo credit: Henrik Drake.
