Life on Earth may have originated in carbonate-rich lakes with high levels of phosphorus, an essential element for life as we know it. This is the conclusion of a new study conducted by two researchers from the Department of Earth and Space Sciences at the University of Washington, Seattle, Jonathan Toner and David Catling.
Toner himself speaks of a real “phosphate problem”, a question not fully resolved with regard to the very origin of life on our planet. In the new study, published in Proceedings of the National Academy of Sciences, attention is therefore drawn to phosphorus, one of the six chemical elements at the basis of life that can have many essential roles in our body (for example it can be considered a basic element of the backbone and molecules of DNA and RNA).
The problem mentioned by Toner lies in the fact that life needs a lot of phosphorus, an element that in the primordial Earth, according to the dominant theories, should not be so available. Focusing, however, on lakes rich in carbonates, also known as alkaline lakes, researchers have noticed a particular phenomenon: these lakes usually form in dry environments, inside real depressions that help the water to escape. However, due to the high evaporation rates, these same waters begin to become very salty from alkaline and to assume a high pH. These lakes are currently still very widespread around the world.
Researchers have carried out laboratory experiments with carbonate-rich water in different chemical compositions and found that these waters show a high presence of phosphorus precisely because of carbonate. Carbonate binds with calcium, leaving part of the phosphate unattached and freely available in the water. A fairly simple idea but still fascinating, as Toner himself suggests.
According to David Catling, the other author of the study, these very high levels of phosphate in lakes and ponds would then have favored the reactions that led phosphorus to be the basis of RNA, proteins and fats, basic elements for life.
These lakes, then, in the period of origin of life, about 4 billion years ago, would have been very numerous also because of the high level of carbon dioxide in the air. In addition, carbon dioxide itself tends to dissolve in water, raising the level of acidity and promoting the release of phosphorus from the rocks, increasing the presence of this element.
This was not a rare phenomenon since the primitive Earth was volcanically very active and therefore fresh volcanic rock tended to react with carbon dioxide increasing the presence of carbonate and phosphorus in the lakes, as Toner himself makes clear that in the primordial Earth lakes rich in carbonates were not at all an exception but the rule.