Hydrogen production from mechanically-activated basalt under experimental conditions simulating subglacial environments

Abstract

Shearing of rocks containing silicate followed by reaction with water has previously been shown to produce hydrogen under experimental conditions relevant to subglacial environments. The abiotic production of hydrogen, carbon dioxide, methane, and other hydrocarbon gases has also been demonstrated in laboratory comminution experiments on rocks from glaciated catchments. Thus, the generation of these biologically useful gases (e.g. hydrogen and methane) beneath glaciers could serve as a source of reductant capable of sustaining microbial ecosystems beneath the ice. Despite the ubiquitous nature of basalt on both Earth and other planetary bodies, production of hydrogen and other gases from basalt through mechanical shearing and reaction with water has not been demonstrated. Basalts were collected from glaciated catchments in Iceland to test whether hydrogen and other gases were produced under laboratory conditions simulating glacial comminution. Rock samples were milled under an inert atmosphere, after which water was added and hydrogen and methane production measured over time. An average of 6.6 nmol hydrogen and 2.6 nmol methane per gram rock were produced after 168 hours from basalt samples tested; additionally, hydrogen peroxide and radicals were produced during grinding. The abiogenic production of hydrogen and methane under these simulated subglacial basaltic environments demonstrated in this study also has implications for supporting subglacial microbial communities during periods of extended glaciation, such as glacial-interglacial cycles in the Pleistocene and during the pervasive low-latitude glaciation of the Cryogenian. This mechanism of hydrogen production also has implications for the potential for life on icy worlds like Mars.