Findings Could Have Implications For Life On Mars And Other Planets
A critical chemical reaction previously thought to support microbial life deep below Earth's surface, and possibly on Mars, is in fact highly unlikely. The findings are reported in this week's issue of the journal Science by researchers funded by the National Science Foundation (NSF)'s Life in Extreme Environments (LeXeN) program and affiliated with the University of Massachusetts at Amherst (U. Mass.).
"This is an important step forward in our continuing efforts to understand the processes that sustain life deep beneath the earth's surface," says Mike Purdy, director of NSF's LeXeN program. "Negative findings like this are as important as positive ones in their importance to our understanding of the processes that determine the limits to life."
It had been generally accepted by scientists that hydrogen gas produced from rock could provide energy to support the growth of microorganisms living below Earth's surface, says U. Mass. microbiologist Derek Lovley. The hydrogen was thought to be produced when basalt, a common form of rock, reacts with water.
However, a research team led by Lovley has found that this concept is incorrect. Although hydrogen gas can be produced from basalt under artificial laboratory conditions, there is no hydrogen production under the conditions actually found in Earth's subsurface.
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."