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The discovery of ancient hydrogen-rich water in extremely remote areas has led to a “quantum change” in our understanding of how much of the Earth’s crust could support life, scientists have said.
The water was discovered trapped kilometres below Earth’s surface in rock fractures in Canada, South Africa, and Scandinavia. It has been described as a “sleeping giant” in terms of its potential to provide energy for life.
The study, to be published in Nature tomorrow, includes data from 19 different mine sites that were explored by Sherwood Lollar, a geoscientist at U of T’s Department of Earth Sciences, U of T senior research associate Georges Lacrampe-Couloume and colleagues at Oxford and Princeton universities.
The researchers also explain how two chemical reactions combine to produce substantial quantities of hydrogen, doubling estimates of global production from these processes that had previously been based only on hydrogen coming out of the ocean floor.
“This represents a quantum change in our understanding of the total volume of Earth’s crust that may be habitable,” said Lollar.
“Until now, none of the estimates of global hydrogen production sustaining deep microbial populations had included a contribution from the ancient continents. Since Precambrian rocks make up more than 70 percent of the surface of Earth’s crust,” Lollar likens these terrains to a sleeping giant. “A huge area that has now been discovered to be a source of possible energy for life,” she said.
One process, known as radiolytic decomposition of water, involves water undergoing a breakdown into hydrogen when exposed to radiation. The other is a chemical reaction called serpentization, a mineral alteration reaction that is common in such ancient rocks.
This study has important implications for the search for deep microbial life. Quantifying the global hydrogen budget is key to understanding the amount of the Earth’s biomass that is in the subsurface, as many deep ecosystems contain chemolithotrophic — so-called “rock-eating” — organisms that consume hydrogen. In the deep gold mines of South Africa, and under the sea, at hydrothermal vents where breaks in the fissure of Earth’s surface that release geothermally heated waters — hydrogen-rich fluids host complex microbial communities that are nurtured by the chemicals dissolved in the fluids. This study identifies a global network of sites with hydrogen-rich waters that will be targeted for exploration for deep life over the coming years.
Further, because Mars — like the Precambrian crust — consists of billions-of-year-old rocks with hydrogen-producing potential, this finding has ramifications for astrobiology. “If the ancient rocks of Earth are producing this much hydrogen, it may be that similar processes are taking place on Mars,” said Lollar.
Agencies/Canadajournal
