"Thermochronologic perspectives on the deep-time evolution of the deep biosphere": Results of this study by H. Drake and P. Reiners appear on the Nov 9th 2021, Proceedings of the National Academy of Sciences.

Nov. 4, 2021

   Figure Caption:   These rocks at Sweetwater Gap in the Granite Mountains in Wyoming are part of the Wyoming Craton, a landscape dominated by 2.8 billion-year-old granite.

The Earth’s deep biosphere is one of the least explored and understood environments. It hosts microbial lineages that are of interest for understanding the origin and evolution of life on our planet. Understanding the history of these microbial communities requires assessing the complex evolution of habitable conditions. This study Henrik Drake, an associate professor at the Linnaeus University in Sweden and Peter Reiners, a professor of geosciences and associate dean of the University of Arizona College of Science,  present the first thermochronological perspective on the habitability of Earth’s Precambrian cratons through time and suggests that the longest record of continuous habitability to the present does not stretch much beyond 1 billion years. This thermochronologic approach provides context for prospecting and interpreting the little-explored geologic record of the deep biosphere of Earth’s cratons and points to candidate areas for the oldest records of subsurface microorganisms.  

 Reiners and Drake focused on Precambrian cratons, which are some of the oldest rocks still present today, to find out where and when subsurface microbes should have been active on Earth hundreds of millions to billions of years ago. The results of their study, published this week in the Proceedings of the National Academy of Sciences, reveal that many cratons were uninhabitable for microbes for much of their existence, with the longest period of habitability not much beyond a billion years, and many cratons have only been habitable for the past 50 million to 300 million years.

An interview with Prof Peter Reiners appears in the University of Arizona News today, and can be found here.