If you’ve ever found stuff mysteriously growing around the jets of your hot tub, you may agree with many scientists who believe life on earth sprang from springs – specifically, deep sea hot springs where hydrothermal vents cooked up life in metabolic reactions between a variety of chemicals. The Proceedings of the National Academy of Science reports on a recent study to test this so-called “metabolism first” hypothesis.
“Metabolism first” differs from the theories that life was brought here by an asteroid or that genetic material developed first. It is based on the idea that hydrogen, carbon dioxide, and sulfur emerged in a black smoke-like cloud from deep sea geysers and combined to form methanethiol, a simple sulfur-containing carbon compound that may have been the bridge between a chemical, non-living world and the first microbial life – like a starter dough. If this is true, today’s hydrothermal vents should also be ovens for this methanethiol bread of life.
Between 2008 and 2012, geochemists Eoghan Reeves, Jeff Seewald, and Jill McDermott at Woods Hole Oceanographic Institution (WHOI) identified high-potential hydrothermal environments along the Mid-Atlantic Ridge, Guaymas Basin, East Pacific Rise and Mid-Cayman Rise where they collected and analyzed 38 hydrothermal fluids for the presence of methanethiol.
What the team found surprised them. There was very little methanethiol in high-hydrogen environments similar to what Earth was like 3.8 billion years ago. However, the amount of methanethiol was high in lower-temperature, low0hydrogen environments. Along with the presence of ammonia, this suggests that existing life forms were being cooked rather than new life being created. In other words, the “starter dough” needs its own starter dough – microbial life forms.
We still don’t have the answer to how life began on earth. However, Eoghan Reeves is excited that this research will help search for life elsewhere.
The upside is, now we have a pretty simple marker for life. Someday if we can land a rover on the ice-covered oceans of Jupiter’s moon Europa – another place in the Solar System that may host hydrothermal vents, and possibly life – and successfully drill through the ice, the first thing it should probably try to measure is methanethiol.
All we need now is some NASA starter dough to find life’s starter dough.