Marine sediment samples used in the irradiation experiments.
\nPhoto courtesy of Justine Sauvage<\/figcaption><\/figure>\nThe process driving the research team\u2019s findings is radiolysis of water \u2013 the splitting of water molecules into hydrogen and oxidants as a result of being exposed to naturally occurring radiation. Steven D\u2019Hondt, URI professor of oceanography and a co-author of the study, said the resulting molecules become the primary source of food and energy for the microbes living in the sediment.<\/p>\n
\u201cThe marine sediment actually amplifies the production of these usable chemicals,\u201d he said. \u201cIf you have the same amount of irradiation in pure water and in wet sediment, you get a lot more hydrogen from wet sediment. The sediment makes the production of hydrogen much more effective.\u201d<\/p>\n
Why the process is amplified in wet sediment is unclear, but D\u2019Hondt speculates that minerals in the sediment may \u201cbehave like a semiconductor, making the process more efficient.\u201d<\/p>\n
The discoveries resulted from a series of laboratory experiments conducted in the Rhode Island Nuclear Science Center. Sauvage irradiated vials of wet sediment from various locations in the Pacific and Atlantic Oceans, collected by the Integrated Ocean Drilling Program and by U.S. research vessels. She compared the production of hydrogen to similarly irradiated vials of seawater and distilled water. The sediment amplified the results by as much as a factor of 30.<\/p>\n
\u201cThis study is a unique combination of sophisticated laboratory experiments integrated into a global biological context,\u201d said co-author Arthur Spivack, URI professor of oceanography.<\/p>\n
The implications of the findings are significant.<\/p>\n
\u201cIf you can support life in subsurface marine sediment and other subsurface environments from natural radioactive splitting of water, then maybe you can support life the same way in other worlds,\u201d said D\u2019Hondt. \u201cSome of the same minerals are present on Mars, and as long as you have those wet catalytic minerals, you\u2019re going to have this process. If you can catalyze production of radiolytic chemicals at high rates in the wet Martian subsurface, you could potentially sustain life at the same levels that it\u2019s sustained in marine sediment.\u201d<\/p>\n
Sauvage added, \u201cThis is especially relevant given that the Perseverance Rover has just landed on Mars, with its mission to collect Martian rocks and to characterize its habitable environments.\u201d<\/p>\n
D\u2019Hondt said the research team\u2019s findings also have implications for the nuclear industry, including for how nuclear waste is stored and how nuclear accidents are managed. \u201cIf you store nuclear waste in sediment or rock, it may generate hydrogen and oxidants faster than in pure water. That natural catalysis may make those storage systems more corrosive than is generally realized,\u201d he said.<\/p>\n
The next steps for the research team will be to explore the effect of hydrogen production through radiolysis in other environments on Earth and beyond, including oceanic crust, continental crust and subsurface Mars. They also will seek to advance the understanding of how subsurface microbial communities live, interact and evolve when their primary energy source is derived from the natural radiolytic splitting of water.<\/p>\n
This study was supported by the U.S. National Science Foundation and the U.S. National Aeronautics and Space Administration. The project is also affiliated with the Center for Dark Energy Biosphere Investigations.<\/p>\n","protected":false},"excerpt":{"rendered":"
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