Evidence of gases similar to those that may have played a part in the formation of the earliest life on the planet has been found by a University of Toronto geochemist.
Until now, it has been assumed that any evidence of the abiogenic, or non-life-based, reactions that created the first simple hydrocarbons on the early Earth had been erased by the organic reactions that have dominated Earth since the evolution and proliferation of complex life.
However, Barbara Sherwood Lollar, a professor in the department of geology and lead researcher of the study published in the April 4 issue of Nature, has found evidence of abiogenic gases in underground mines. Life on Earth probably began from simple organic compounds, including hydrocarbons that were formed from abiogenic reactions involving water, carbon dioxide and methane.
Hydrocarbon gases have been found in deep rocks and groundwaters at sites throughout the Canadian Shield and in Scandinavia and southern Africa. "All of these areas are geologically similar, made of Precambrian rocks which are billions of years old," she says. The gases are usually trapped in fracture systems throughout the rock and are released when mine drilling penetrates these rocks.
Gases from mines have been reported anecdotally from miners as far back as the 1880s, says Sherwood Lollar, but their origin was a mystery. "Gases are usually formed through microbial, or thermogenic processes (which create oil and natural gas fields) but neither of these processes was thought to occur in Precambrian rocks two kilometres under the Earth's surface, which is the depth that our samples came from."
Sherwood Lollar and her team examined certain gases from a mine near Timmins, Ont. Analyses of the gases' carbon and hydrogen isotope ratios found that the gases matched hydrocarbons known to be the result of abiotic reactions. "Until now, these types of gases had only been known through laboratory experimentation, and from extraterrestrial samples such as meteorites," Sherwood Lollar says.
The presence of these hydrocarbon gases deep in the earth raises another exciting possibility, Sherwood Lollar says. "In recent years it has been discovered that life on Earth extends far deeper than ever thought possible. Deep microbial communities have been discovered several kilometres under the Earth's surface and debate has raged over what these microbes could be using as a food source."
According to Sherwood Lollar, the hydrocarbon and hydrogen gases could be a food source. "These deep biosphere bacteria could 'digest' the gases through a form of chemosynthesis - similar to that known to support life at the deep sea vents - using the chemicals in the gases in order to get energy for life."
Funding for this study was provided by the Natural Sciences and Engineering Research Council of Canada and in part by Falconbridge Ltd.
CONTACT:
Lanna Crucefix
U of T Public Affairs
416-978-0260
lanna.crucefix@utoronto.ca
Professor Barbara Sherwood Lollar
Department of Geology
416-978-0770
bsl@quartz.geology.utoronto.ca
Journal
Nature