The Origins of Life: Key Chemical Reactions May Have Begun in Hot, Cracked Rocks

Chemical reactions key to the origin of life on Earth may have occurred as molecules moved along a temperature gradient within a network of cracks in thin rocks deep underground.

Such networks are thought to have been common on early Earth and may have provided a kind of natural laboratory in which many of the building blocks of life were concentrated and separated from other organic molecules.

“It’s very difficult to get a more general environment where you can do these cleansing and intermediate steps,” he says. Christophe Mast at Ludwig-Maximilians-University in Munich, Germany.

He and his colleagues created a heat flow chamber the size of a playing card to model how mixtures of organic molecules behave in cracks in such rocks.

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

During an 18-hour experiment in a heat flow chamber, we found that different molecules were concentrated in different parts of the chamber depending on their sensitivity to thermophoresis. Among these molecules are many amino acids and A, T, G, and C nucleobases, which are important building blocks of DNA. This effect was further magnified by creating a network of three interconnected chambers, with one side of the chamber network at 25°C and the other side at 40°C. Additional chambers further concentrated the compounds concentrated in the first chamber.

Mathematical simulations with 20 interconnected chambers (which may closely resemble the complexity of natural crack systems) find that the enrichment of different molecules can be further amplified Did. In one chamber, the amino acid glycine reached a concentration approximately 3000 times higher than that of another amino acid, isoleucine, even though they entered the network at the same concentration.

The researchers also demonstrated that this enrichment process can cause reactions that would otherwise be extremely difficult. They showed that glycine molecules can bind to each other when the concentration of a molecule that catalyzes the reaction called trimetaphosphoric acid (TMP) increases. Mast said TMP is an interesting molecule to concentrate because it was rare on early Earth. “Since [the chambers] Since they are all randomly connected, all kinds of reaction conditions can be implemented. ”

“It’s very interesting that within the crack there are regions with different proportions of compounds,” he says. evan sprite from Radboud University in the Netherlands was not involved in the study. “This enhancement allows us to create even more versatility from very simple building blocks.”

But enrichment in rock fractures is still far from a viable scenario for the origin of life, he says. “Ultimately, they still need to come together to form something resembling a cell or protocell.”