������Ƶ

A team of scientists from the ������Ƶ and Manchester University in the United Kingdom have gone three kilometres beneath the surface of the Canadian Shield to find some of the oldest fluids in our planet’s history. The waters are rich in clues about lives lived without sunlight on Earth and possibly on Mars. 

“The saline waters bubbling out of fractures in the rocks are not unlike the black smoker fluids found at deep sea hydrothermal vents,” said University Professor Barbara Sherwood Lollar, a geochemist in U of T’s Department of Earth Sciences. “The water is the product of geochemical reactions with the rock and contains dissolved hydrogen, as well as noble gases – helium, neon, argon and particularly xenon – that have been trapped since early in Earth’s history.”

Noble gas isotopes from radiogenic reactions in the rock accumulate in water over time enabling scientists to calculate that these waters have collected the by-products of water-rock interaction for more than a billion years – possibly even back to the formation of these ancient rocks more than 2.7 billion years ago. Their discovery will be published in the May 16 issue of Nature.

The team behind this latest discovery is part of the same group that identified some of the deepest chemolithotrophic – rock and chemical-eating – microbial communities found to date. In 2006, at 2.8 km below the surface in South African gold mines, they found hydrogen-utilizing sulfate-reducing microbes eking out an existence in saline fracture waters that have been cut off from the sun for tens of millions of years.

“The ancient waters of the Canadian Shield contain abundant chemicals that we know microbes can use as energy in the absence of sunlight-driven photosynthesis,” said Sherwood Lollar. “This shows that ancient rocks have the potential to support life and this could be the case whether they are three kilometres below the Earth’s surface or below the surface of Mars.”   

Large regions of Mars are made up of terrain like that of the Earth’s Precambrian Shield – billions of years-old rocks with similar mineralogy.

The Canadian Shield discovery puts the age of the fluids much farther back in time than the South Africa discovery, identifying a groundwater system that has been isolated from the planet’s surface for billions, rather than tens of millions of years. “Our discovery establishes that ancient fluids, hitherto thought to have survived only in microscopic fluid inclusions trapped in the rocks, may instead still flow from ancient fractures,” said Sherwood Lollar.

Sherwood Lollar says the team hopes answers can be found to other pressing questions such as: How widespread are ancient fluids trapped in the subsurface? What range of fluid ages might be preserved in the Canadian Shield and in billions-year-old rocks worldwide? How do microbes, if any can be found, in these very ancient fluids compare to those discovered in South Africa, and to surface life?

“These are like trapped time capsules,” said Sherwood Lollar. “They may tell us about the atmosphere 2.7 billion years ago, and about the fluids that formed the valuable ore deposits that are the foundation of Canada’s mineral wealth.”

Team members include co-principal investigator Sherwood Lollar and her postdoctoral fellow Long Li, co-principal investigator Christopher Ballentine and postdoctoral fellow Greg Holland, both of the University of Manchester, and Greg Slater from McMaster University.

Funding was provided by a Discovery grant from Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs Program, the National Environment Research Council in the UK and the Deep Carbon Observatory Deep Energy Project.

Kim Luke writes for the Faculty of Arts & Science.

(Image above of U of T  postdoctoral researcher K. Voglesanger measuring geochemistry of the deep fluids by K. Voglesanger)