Ancient clay may be a piece in puzzle to how life on Earth began

An ancient clay mineral called greenalite that formed deep in the ocean, near hot seafloor vents, may have played a crucial role in the emergence of life on Earth, researchers from The University of Western Australia and California Institute of Technology have found. The research was published in Astrobiology.

UWA researchers Professor Birger Rasmussen and Dr Janet Muhling and Professor Woodward Fischer from California Institute of Technology, have been studying the iron-rich clay greenalite. It was deposited in the ancient ocean in rocks known as banded iron formations, which formed more than 2.4 billion years ago, and are now mined around the world for their iron ore.

Greenalite forms tiny, free-floating particles when hot fluid emitted from seafloor vents mix with cooler seawater.

Professor Rasmussen said the scientists probing life’s origins had long searched for crystals capable of allowing small organic molecules to form on to their surface, helping form large complex molecules such as RNA integral to the formation of early life on Earth.

“Greenalite has not been considered before in origins-of-life research. However, our study suggests it was not only in the right place at the right time, it was also the right size and had the right crystal structure to help the assembly of primitive cells.”

Professor Birger Rasmussen

Unlike other minerals, greenalite has parallel grooves on its surface that are about 2.2 nanometers wide and up to 100 nanometers long.

“When we compared the size of the grooves to the diameter of the helix of RNA and DNA, which is about 2.0 nanometers, we were amazed. It quickly became apparent that long chains of RNA could fit snuggly into the grooves on greenalite,” Professor Rasmussen said.

“We suspect that the grooves may have served as primitive assembly lines for producing RNA molecules. The length of the grooves would have been sufficient to assemble RNA molecules long enough to replicate and catalyse biochemical reactions.

“What’s more, because greenalite forms in conditions believed to be common in the earliest oceans on Earth, it is possible that greenalite formed on other wet rocky planets, such as Mars.”

Professor Rasmussen said unlike Earth, the surface of Mars contained deposits of hydrothermal clay that could be more than 3.7 billion years old and it was possible that ancient muds on Mars preserved evidence for prebiotic organic synthesis that had long been destroyed on Earth by plate tectonics.

“The next step is to carry out experiments to investigate the role of greenalite in the formation of primitive cells. Initial experiments have already started and while promising, there is a long way to go before we generate life in a test tube,” Professor Rasmussen said.

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