19-09-03 As scientific revolutions go, Thomas Gold's idea seemed to have it all, from a catchy name to the promise of vast riches. "The Deep Hot Biosphere," as the distinguished Cornell University physicist calls the theory he developed in the 1980s, is the notion the Earth's rocky crust teems with bacteria that live on hydrocarbon gases.
These gases, the precursors of oil and natural gas, rise up from even deeper within the Earth, where they are created in reactions powered by the planet's own heat. If we could tap into them, so the theory goes, we would have a virtually limitless source of energy.

Over the last decade, the idea was met with equal parts interest and ridicule. If his theory were true, it would change the world. The oil and gas left over from decomposed ancient forests and sea life -- currently the only known deposits --would have been a mere footnote to the Earth's total supply, because natural gas would be a renewable resource. Every country in the world would have its own source ofoil, so long as it could drill deep enough.
An international team of scientists is meeting to plan the research projects for one of the deepest holes to be dug in Canada, a project that aims to probe the lasting mysteries about the ore-rich rock of the Canadian Shield and the ancient life within it. They do not expect to find the endless source of fuel -- this aspect of the Deep Hot Biosphere has been all but discredited -- but they might be able to settle other questions Gold raised.

He was certainly on to something. He was the first to prove microbes do indeed live several kilometres down, enduring extreme pressure and heat. But last year, Canadian scientists working in a copper and silver mine near Timmins helped prove him wrong about the oil and gas.
When miners drill into the Canadian Shield, the swath of ancient rock stretching from Labrador to Alberta, they often hear a sound like a can of pop opening. On testing, this proves to be methane being released from the rock. But if, as most geologists believe, such gases are produced only by decaying organic material, they should not be trapped in the rock of the Shield, which predates all but the most primitive life forms.

The researchers found methane is in fact produced without decaying forests, but it does not come from deep within the Earth's core, as Gold proposed. It is the bacteria that convert methane from carbon dioxide, though not enough to be commercially relevant. What's more, different bacteria at similar depths -- thousands of metres -- feed off this same methane.
The finding offers an alternate explanation for the discovery of hydrocarbon gas in the Canadian Shield, one that does not involve a Goldian rethinking of classical geology. But the rock-dwelling bacteria might still have secrets to reveal.

The reactions between simple bacteria and carbon dioxide to produce methane are strikingly similar to those that would have taken place on Earth before the evolution of life, so to understand them -- how the waste of one bacterium can be the food for another -- might offer insights into the earliest ages of the bio-sphere. Research into life in such improbable places, like bedrock, thermal ocean vents and the extreme cold of polar ice, is a blossoming scientific field with applications being tested in alternative fuel sources and industrial chemistry.
Michael Lesher, a geology professor at Laurentian University in Sudbury, is one of the lead scientists on the Sudbury Deep Drilling Project, a proposed 6-km-deep hole to be dug in a northern area of the city. That would put it right in the middle of the Sudbury Basin, which was created by a meteorite impact almost 2 bn years ago.

The international team of geologists and other Earth scientists is awaiting word on funding from the Canadian government and the Germany-based International Continental Scientific Drilling Program. The drilling is expected to cost about $ 125 per meter. Dropping into the Earth with a 76-millimetre-wide drill bit, the team hopes to push through the few metres of top soil, then plough through the roughly 1.5 km of sedimentary black shale at about 90 metres a day. Past this, they will reach the "fallback breccia" rock of the Onaping Formation, the crater.
It is at this point that the real geology can begin, and Lesher said plans call for a "down-hole laboratory" to be built at the site, with devices to measure the stresses on the rock caused by the shifting of the Earth's crust -- a key concern for future mining efforts. Lesher envisions the Sudbury hole as "a permanent window into the upper crust."

The drill will have to slow as it reaches the upper part of the primary object of study, the Sudbury Igneous Complex. At the bottom of this is where most of the nickel, copper and platinum ore deposits that form the foundation of Sudbury's economy are most likely to be found.
Theories vary as to whether this bottom is at 5 km or 10 km. Greg Slater, a professor of geology at McMaster University in Hamilton and a member of the team that studied the methane last year, will lead the study of the bacteria along with Barb Sherwood Lollar of the University of Toronto and Gordon Southam of the University of Western Ontario.

At the greatest depth of the hole, roughly 6 km, he expects temperatures to hit 80 degrees Celsius to 100 degrees Celsius -- hot enough to boil water, but still a few degrees below the agreed-upon 120 degrees Celsius limit for the hardiest microbes. Learning their survival techniques, and how some of them create methane from the raw material of the Earth, might also offer hope for Gold's partial vindication. Even though he appears to have been wrong about an endless source of natural gas, his discovery of the "deep biosphere," as these bacteria have come to be known, has direct implications for the search for life on Mars and other planets.
Writing in 1992, he observed: "Subsurface life may be widespread among the planetary bodies of our solar system, since many of them have equally suitable conditions below, while having totally inhospitable surfaces. One may even speculate that such life may be widely disseminated in the universe."