The age of the Earth is about 4.54 billion years. It is believed that life arose on it at least a billion years later, that is, 3.5 billion years ago – in any case, everyone agrees that life already existed by these 3.5 billion. However, recently there are studies that seem to increase the age of terrestrial life – yes, it already existed 3.5 billion years ago, but it actually arose earlier.
In 2017 employees University College London published in Nature an article that described microscopic glandular tubes 4.28–3.77 billion years old – these tubes, according to the researchers, could have been made by bacteria or some kind of bacteria-like organisms. Not everyone was convinced by those results, and now the same group of researchers is publishing a new article in Science Advances with similar conclusions: life on Earth could have arisen as little as 300 million years after the Earth itself arose.
The material was the same ancient quartz rocks, formed 4.28–3.77 billion years ago and excavated in the Canadian province of Quebec. As before, rock samples were cut into the thinnest sheets to reveal structures of hematite, or red ironstone. Only now these sheets were about 100 micrometers thicker than in the first work, because now the researchers expected to find larger traces of ancient bacteria.
Such traces were found – in the form of threads, wavy, twisted, branching and parallel to each other, as well as in the form of irregular spheres. They were studied in various ways, using Raman spectroscopy, computer microtomography, and also using a special method, when layers of 200 nanometers thick are cut off from the sample, and the electron microscope simultaneously looks at how the sample has changed after such an operation. Then a set of obtained images were combined into a three-dimensional model. According to this model, the wavy twisted, wavy, etc., filaments turned out to be very similar to those that remain after modern microbes living near hydrothermal vents at the bottom of the Arctic and Indian Oceans and near the Loihi volcano in Hawaii. Ancient (proto)microbes also consumed iron escaping from hydrothermal crevices; this iron, having passed through the metabolism of bacteria, was deposited in the form of hematite threads, in which at the same time traces of organic carbon remained.
When it comes to such ancient geological formations, the question always arises – maybe what looks like traces of life was actually formed due to geochemical transformations? However, in this case, the authors of the work argue that, based on the structure of quartz, in which hematite traces are imprinted, one can more or less confidently say that they are of biological origin.
As we said above, there are other studies that are trying to “age” earthly life. For example, there is evidence that graphite particles mined from geological layers 3.95 billion years old are also of biological origin; these particles were found on the Labrador Peninsula. (Canada is generally lucky to see the most ancient; last year we wrote that traces of the most ancient animal were also found on its territory.) However, often reports of the “most ancient life” are subsequently disavowed, so trouble with these hematite threads.
Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.
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