Life’s vital chemistry may have begun in hot, cracked rock

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Some amino acids may become concentrated while traveling through cracks in the hot rock

Sebastian Kaulitzky/ Alamy

Chemical reactions critical to the origin of life on Earth may have occurred when molecules move along thermal gradients within networks of thin rocks deep underground.

Such networks, which would have been common on the early Earth, could provide a kind of natural laboratory in which many of the building blocks of life were concentrated and isolated from other organic molecules.

“It’s very difficult to get a more normal environment where you can have these purification and intermediate steps,” says Christophe Mast At Ludwig Maximilian University of Munich in Germany.

He and his colleagues built a heat flow chamber the size of a playing card to investigate how a mixture of organic molecules might behave in such rock fractures.

They heated one side of a 170 micrometer thick chamber to 25 °C (77 °F) and the other to 40 °C (104 °F), creating a temperature gradient along which molecules would move in a process called thermophoresis. How sensitive a molecule is to this process depends on its size and electrical charge and how it interacts with the fluid in which it is dissolved.

In an 18-hour experiment in a heat flow chamber, they found that different types of molecules were concentrated in different parts of the chamber according to their sensitivity to thermophoresis. These molecules contained several amino acids and the A, T, G and C nucleobases, which are a major component of DNA. This effect was further enhanced when they created a network of three interconnected chambers, again with one side of the chamber network at a temperature of 25°C and the other side at a temperature of 40°C. Additional chambers further enriched the compounds previously concentrated.

In a mathematical simulation with 20 interconnected chambers, which could better resemble the complexity of the natural system of fractures, they found that the enrichment of different molecules could be reproduced. In one chamber, the amino acid glycine reached a concentration approximately 3000 times higher than that of a different amino acid, isoleucine, despite entering the network at the same concentration.

The researchers also demonstrated that this process of enrichment may be able to generate a response that would otherwise be extremely challenging. They showed that increasing the concentration of a molecule that catalyzes the reaction, called trimetaphosphate (TMP), enabled glycine molecules to bind to each other. Mast says, TMP is a noteworthy molecule to enrich because it would have been rare on the early Earth. “since [the chambers] All randomly connected, you can implement all kinds of reaction situations.

“It is extremely interesting to have areas in the crack containing different proportions of compounds,” says ivan spruijt at Radboud University in the Netherlands, who was not involved in the research. “You can create more variety from very simple building blocks with this added enrichment.”

However, he says that enrichment in rock fractures is still far from a viable scenario for the origin of life. “In the end, they still need to come together to form anything like a cell or protocell.”


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