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In 2009, scientists from Woods Hole Oceanographic Institution embarked on a NASA-funded mission to the Mid-Cayman Rise in the Caribbean, in search of a type of deep-sea hot-spring or hydrothermal vent that they believed held clues to the search for life on other planets. They were looking for a site with a venting process that produces a lot of hydrogen because of the potential it holds for the chemical, or abiotic, creation of organic molecules like methane – possible precursors to the prebiotic compounds from which life on Earth emerged.   

For more than a decade, the scientific community has postulated that in such an environment, methane and other organic compounds could be spontaneously produced by chemical reactions between hydrogen from the vent fluid and carbon dioxide (CO₂).  The theory made perfect sense, but showing that it happened in nature was challenging.

Now we know why:  an analysis of the vent fluid chemistry proves that for some organic compounds, it doesn’t happen that way.

New research by geochemists at Woods Hole Oceanographic Institution, published June 8 in the Proceedings of the National Academy of Sciences, is the first to show that methane formation does not occur during the relatively quick fluid circulation process, despite extraordinarily high hydrogen contents in the waters.  While the methane in the Von Damm vent system they studied was produced through chemical reactions (abiotically), it was produced on geologic time scales deep beneath the seafloor and independent of the venting process. Their research further reveals that another organic abiotic compound is formed during the vent circulation process at adjacent lower temperature, higher pH vents, but reaction rates are too slow to completely reduce the carbon all the way to methane.