October 2004

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WASHINGTON, DC - Experiments and calculations performed at four research institutions open prospects that hydrocarbons - methane - may be formed by inorganic materials under enormous pressures deep down in the earth.

The findings don’t invalidate the traditional view that hydrocarbons are produced from decaying organic matter, but it opens up a second explanation of their origin. This concept was first proposed decades ago by the late Thomas Gold, an astrophysicist with many unconventional ideas who believed that hydrocarbons are constantly produced at great depth. (H&FCL’s precursor, “The Hydrogen Letter,” reported in January 1987 on Gold and an experiment in Sweden that he had initiated).

The new, highly technical, paper, “Generation of methane in the Earth’s mantle: In situ high pressure-temperature measurements of carbonate reduction,” was published in the Sept. 13-17 early, on-line edition of the “Proceedings of the Natural Academy of Sciences.” Essentially, the scientists at the Carnegie Institution, the Carnegie-managed High Pressure Collaborative Access Team at Argonne National Laboratory, and at Indiana University South Bend performed experiments that mimicked conditions in the earth’s upper mantle, a region 20 to 60 km underneath the earth’s crust beneath the continents. Lawrence Livermore National Laboratory did the calculations.

Huge Pressures, Temperatures Cook Materials

Using a diamond anvil cell, a device previously used at the Carnegie institution to make metallic hydrogen (THL May 87, July 94, H&FCL March 95), the scientists squeezed common materials - iron oxide (FeO), calcite (CaCO3) and water - to pressures ranging from 50,000 to 110,000 times of the atmospheric pressure at sea level and heated the samples to temperatures of up to 2,700 deg. F (1,500 deg. C).

They found methane formed by reducing the carbon in calcite over a wide range of temperatures and pressures. Results were best at about 1,000 deg. F. and pressures of less than 70,000 times atmospheric.

These new experiments now “point to the possibility of an inorganic source of hydrocarbons at great depth in the earth,” the Academy’s release quoted co-author Dr. Russell Hemley of Washington’s Carnegie Institution’s Geophysical Laboratory as saying. Team leader Dr. Henry Scott of Indiana University added, while “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.”

Dr. Freeman Dyson, professor emeritus at the Institute for Advanced Study at Princeton University who reviewed the paper said it was important not because it settled the question of how exactly natural gas and petroleum originates, but because it provides the 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.” Contacts: Nat’l Academy of Sciences (media) Weikny Johnson, 202/334-3382; Dr. Henry Scott, hpscott@iusb.edu.