AMHERST, Mass. - Scientists at the University of Massachusetts and the U. S. Geological Survey (USGS) have discovered that a critical chemical reaction previously thought to support microbial life deep below the Earth’s surface, and possibly on Mars, is in fact highly unlikely. The findings are reported in the August 14 issue of the journal Science.
It had been generally accepted by scientists that hydrogen gas produced from rock could provide energy to support the growth of microorganisms living below the Earth’s surface, says Derek Lovley, who chairs the UMass department of microbiology. The hydrogen was thought to be produced when basalt, a common form of rock in the Earth’s subsurface, reacts with water. However, a research team led by Lovley has found that this concept is incorrect. They found that although hydrogen gas can be produced from basalt under artificial laboratory conditions, there is no hydrogen production under the conditions actually found in the Earth’s subsurface. The research was funded with a three-year $325,000 grant from the National Science Foundation’s Life in Extreme Environments program.
Lovley and his colleagues found that hydrogen could only be produced from the basalt when the rock was exposed to acidic conditions – but environments containing basalt are never acidic. "The idea that hydrogen produced from rocks could support large subsurface microbial ecosystems on Earth and possibly other planets was fascinating and was accepted by most microbiologists," Lovley says. "Unfortunately, this concept can not be supported by the available data."
From analysis of chemical and microbiological data Lovley and collaborators Robert Anderson, a UMass graduate student, and Francis Chapelle, a hydrologist at the USGS in South Carolina, suggest that microorganisms in the Earth’s subsurface are probably living on organic matter associated with the rock, not hydrogen. This is similar to the way that microorganisms grow in soil on the surface of Earth.
The scientists emphasized that even though the microorganisms living deep in the Earth have the ability to survive in a manner similar to surface microorganisms, they may have other unique characteristics. For example, Lovley’s recent research has demonstrated that microorganisms from the Earth’s subsurface can be used to remove radioactive metals and hydrocarbons from polluted groundwater.