Oceans may contain large reserve of hydrogen gas

Rocks formed beneath the ocean floor by fast-spreading tectonic plates may be a large and previously overlooked source of free hydrogen gas, a new study suggests.
The finding at Duke University in the US could have far-ranging implications since scientists believe free hydrogen gas (H2) might be the fuel source responsible for triggering life on Earth.
If it were found in large enough quantities, some experts speculate that it could be used as a clean-burning substitute for fossil fuels today because it gives off high amounts of energy when burned but emits only water, not carbon.
Recent discoveries of free hydrogen gas, which was once thought to be very rare, have been made near slow-spreading tectonic plates deep beneath Earth's continents and under the sea.

"Our model, however, predicts that large quantities of H2 may also be forming within faster-spreading tectonic plates - regions that collectively underlie roughly half of the Mid-Ocean Ridge," said Stacey L Worman, a postdoctoral fellow at the University of Texas at Austin, who led the study while she was a doctoral student at Duke.
Total H2 production occurring beneath the oceans is at least an order of magnitude larger than production occurring under continents, the model suggests.

"A major benefit of this work is that it provides a testable, tectonic-based model for not only identifying where free hydrogen gas may be forming beneath the seafloor, but also at what rate, and what the total scale of this formation may be, which on a global basis is massive," said Lincoln F Pratson, professor of earth and ocean sciences at Duke, who co-authored the study.

The new model calculates the amount of free hydrogen gas produced and stored beneath the seafloor based on a range of parameters - including the ratio of a site's tectonic spreading rate to the thickness of serpentinised rocks that might be found there.
Serpentinised rocks - so called because they often have a scaly, greenish-brown-patterned surface that resembles snakeskin - are rocks that have been chemically altered by water as they are lifted up by the spreading tectonic plates in Earth's crust.
Molecules of free hydrogen gas are produced as a by-product of the serpentinisation process.
"Most scientists previously thought all hydrogen production occurs only at slow-spreading lithosphere, because this is where most serpentinised rocks are found. Although faster-spreading lithosphere contains smaller quantities of this rock, our analysis suggests the amount of H2 produced there might still be large," Worman added.

The study was published in the journal Geophysical Research Letters.