Photo by Matt Cashore Scott

Editor’s note: Read the entire report discussed in this story online at this Web site:

http://www.pnas.org/cgi/content/full/101/39/14023

Could there be a huge reserve of untapped methane, the main component in natural gas, deep in the earth’s crust? According to a report released in September in the Proceedings of the National Academy of Sciences (PNAS), that possibility may need to be explored more thoroughly.

IU South Bend physics and geology professor Henry Scott was the lead author of the PNAS study, along with Russell Hemley and Ho-kwang Mao, both of the Carnegie Institution’s Geophysical Laboratory, Washington, D.C.; Nobel Laureate Dudley Herschbach of Harvard University; and Lawrence Fried, Michael Howard and Sorin Bastea of the Lawrence Livermore National Laboratory.

As a postdoctoral fellow for the National Research Council, Scott developed a collaborative relationship with this distinguished group of scientists at the Carnegie Institution’s Geophysical Laboratory. Their research involves the formation of hydrocarbons, and Scott continues this work as a faculty member at IU South Bend.

The team of researchers found that there is a possibility of an inorganic source of hydrocarbons deep within the earth from a simple reaction between water and carbon-bearing rock. The traditional theory is that fossil fuel is formed over millions of years from the breakdown of plants and animals. These fossil fuel reserves exist close to the earth’s surface in oil fields.

Often, gas reserves are accompanied by liquid petroleum. Since the first U.S. oil well started to gush in 1859, commercially viable wells of oil and gas commonly have been drilled no deeper than three to five miles into the earth’s crust.

The experiments showed that methane can form independently of living organisms and remain chemically stable at pressures and temperatures similar to conditions at 120 to 180 miles beneath the earth’s surface. The team used a diamond anvil cell (two gem-quality diamonds with flattened tips that are pressed together) to squeeze materials common on the earth’s surface, such as iron oxide, calcite and water, to pressures many thousands of times the pressure of the earth’s atmosphere. The scientists heated the mixture with both a resistive heating method and by focusing laser light up to 2,700 degrees Fahrenheit. Scott’s team has found that methane was produced.

These experiments point to the possibility of an inorganic source of hydrocarbons more than 100 miles down where the pressures and temperatures are extremely high.

“This is an interesting step forward. Although it is well established that commercial petroleum originates from the decay of once-living organisms, these results support the possibility that the deep earth may produce abiogenic hydrocarbons of its own under high-pressure chemical reactions,” Scott said. “These initial results do not prove the extent to which this occurs within the earth, but they spark the imagination” regarding the origin of natural gas and petroleum, and what that means to the future supply of natural resources.

Scott cautioned that their findings do not offer a quick cure for high gas prices or oil politics. “These results in no way alleviate the immediate problems we face regarding our natural resources, but they do suggest that additional research is needed to fully understand how hydrocarbons form in the earth.”

“This paper is important,” remarked Freeman Dyson, professor emeritus at Princeton University’s Institute for Advanced Study, who reviewed the study. “Not because it settles the question whether the origin of natural gas and petroleum is organic or inorganic, but because it gives us tools to attack the question experimentally. If the answer turns out to be inorganic, this has huge implications for the ecology and economy of our planet as well as for the chemistry of other planets.”

The PNASinformation was widely reported online, in science publications and in the popular media such as the New York Times.