Washington: Scientists have discovered evidence of ancient life in Earth's mantle rocks deep below the seafloor, confirming a long-standing hypothesis that interactions between mantle rocks and seawater can create potential for life even in hard rocks.
The fossilised microbes are likely the same as those found at the active “Lost City” hydrothermal field, providing potentially important clues about the conditions that support “intraterrestrial” life in rocks below the seafloor.
“Lost City” is a field of alkaline hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s.
“We were initially looking at how seawater interacts with mantle rocks and how that process generates hydrogen,” said lead researcher Frieder Klein, associate scientist at the US-based the Woods Hole Oceanographic Institution (WHOI).
But during our analysis of the rock samples, “we discovered organic-rich inclusions that contained lipids, proteins and amino acids - the building blocks of life - mummified in the surrounding minerals,” he explained.
According to Klein, confirmation that life is possible in mantle rocks deep below the seafloor may have important implications for understanding subseafloor life across a wide range of geologic environments on planetary bodies.
The team focused on mantle rocks that were originally exposed to seawater approximately 125 million years ago when a large rift split the massive supercontinent known as Pangaea.
The rift, which eventually evolved into the Atlantic Ocean, pulled mantle rocks from Earth's interior to the seafloor, where they underwent chemical reactions with seawater, transforming the seawater into a hydrothermal fluid.
The hydrothermal fluid likely had a high pH (numeric scale used to specify the acidity or alkalinity of a liquid solution) and was depleted in carbon and electron acceptors.
The hydrothermal fluid contained hydrogen and methane and seawater contains dissolved carbon and electron acceptors.
“So when you mix the two in just the right proportions, you can have the ingredients to support life,” Klein noted.
The study, published in the journal Proceedings of the National Academy of Sciences, underscores the influence major geologic processes can have on the prospect for life.
It reinforces the idea that life springs up anywhere there is water, even in seemingly hostile geological environments.
The research was a collaborative effort between Klein, WHOI scientists Susan Humphris, Weifu Guo and William Orsi, Esther Schwarzenbach from Virginia Institute of Technology in the US and Florence Schubotz from University of Bremen in Germany