A reaction between rocks and water may create enough hydrogen "food" to sustain microbial life under Earth's crust, or possibly on Mars, U.S. scientists say.

A study led by the University of Colorado Boulder and published in the journal Nature Geoscience found chemical reactions between iron-containing minerals and water may produce enough hydrogen to feed microbial communities living in pores and cracks within the enormous volume of rock below Earth's ocean floor and parts of the continents.

The findings hint at the possibility hydrogen-dependent life could have existed where iron-rich igneous rocks on Mars were once in contact with water, a CU-Boulder release reported Thursday.

"Water-rock reactions that produce hydrogen gas are thought to have been one of the earliest sources of energy for life on Earth," researcher Lisa Mayhew said.

"However, we know very little about the possibility that hydrogen will be produced from these reactions when the temperatures are low enough that life can survive," she said. "If these reactions could make enough hydrogen at these low temperatures, then microorganisms might be able to live in the rocks where this reaction occurs, which could potentially be a huge subsurface microbial habitat for hydrogen-utilizing life."

Not only is there a potentially large volume of rock on Earth that may undergo these kinds of reactions, but the same types of rocks are prevalent on Mars, Mayhew said.