In the race to know how life finally originated on earth, a thrilling research now reveals that simple metabolic reactions emerged near ancient seafloor hot springs, enabling the leap from a non-living to a living world.
"The recent research is the first to test a fundamental assumption of this 'metabolism first' hypothesis and finds that it may not have been as easy as previously assumed," said geochemist Eoghan Reeves from Massachusetts-based Woods Hole Oceanographic Institution (WHOI).
A central figure in this hypothesis is a simple sulphur-containing carbon compound called "methanethiol" - a supposed geologic precursor of the Acetyl-CoA enzyme present in many organisms, including humans.
Scientists suspected methanethiol could have been the "starter dough" from which all life emerged.
"What we essentially found is that we do not think methanethiol is forming by purely chemical means without the involvement of life. This might be disappointing news for anyone assuming an easy start for hydrothermal proto-metabolism," Reeves explained.
"However, our finding that methanethiol may be readily forming as a breakdown product of microbial life provides further indication that life is present and widespread below the seafloor and is very exciting," he noted.
To directly measure methanethiol, the researchers went to hydrothermal vent sites where the chemistry predicted they would find abundant methanethiol.
In total, they measured the distribution of methanethiol in 38 hydrothermal fluids from multiple differing geologic environments including systems along the mid-Atlantic ridge, Guaymas basin, the East Pacific Rise and the Mid-Cayman Rise.
"Some systems are very rich in hydrogen, and when you have a lot of hydrogen it should, in theory, be very easy to make a lot of methanethiol," Reeves added.
The researchers found an abundance of methanethiol being formed in low temperature fluids where hot black smoker fluid mixes with colder sea water beneath the seafloor.
The presence of ammonia - a byproduct of biomass breakdown - strongly suggests these fluids are 'cooking' existing microbial organic matter.
"The breakdown of existing subseafloor life when conditions get too hot may therefore be responsible for producing large amounts of methanethiol," suggested Jeff Seewald from WHOI.
The researchers believe this new understanding could change how we think about searching for life on other planets.
Their work has been published in Proceedings of the National Academy of Science.