The emergence of life on Earth is perhaps the mostAn interesting question to which there is still no clear answer. Earlier we said that at the origins of the origin of life lay two main forms of the genetic code - DNA and RNA molecules. Biological molecules, despite the fact that they themselves are very complex, consist of fairly simple components. For RNA and DNA, such components are nucleotides, which consist of five nitrogenous bases that perform the functions of the genetic code. When nucleotides are connected to each other, they form a chain of nucleic acids, that is, DNA or RNA. But where did these nitrogenous bases come from? According to some scientists, they could have been brought to Earth with meteorites.
How could the first DNA and RNA appear on Earth?
The main feature of nucleic acidslies in the ability to copy one's own information, thus creating one's own copies. Unlike living biological cells, where various chemical processes are regulated by special proteins called enzymes, RNA molecules do not need enzymes to synthesize their copies.
Therefore, at the very beginning of the origin of life, manyscientists describe our planet as an RNA world, and DNA and proteins came later. For a long time, scientists did not know where the nitrogenous bases that are necessary for the emergence of RNA came from. According to one version, they could have arisen from other molecules - water, hydrogen sulfide and hydrogen cyanide. A study published in the journal Science proves that this is theoretically possible. However, the process is quite complex, requiring certain conditions.
But, it is quite possible that everything happened mucheasier. Starting from the second half of the last century, scientists began to find nitrogenous compounds on meteorites. In particular, some genetic letters were discovered - adenine, guanine and uracil. However, the version about the “meteoritic” origin of RNA was not widely used, since two letters were missing - thymine and cytosine (T and C).
Did life come from outer space?
In a recent study published in the journalNature Communications https://www.nature.com/articles/s41467-022-29612-x, Japanese scientists report that they succeeded in the missing letter on meteorites. Why haven't they been found before? In fact, everything is very simple - thymine and cytosine are very fragile nitrogenous bases. As a result, the methods by which organic matter was previously extracted from meteorites destroyed them. That is, the letters of the genetic code T and C are not at all uncommon.
Modern research methods have allowedto detect on meteorites the carbohydrate ribose, as well as all the nitrogenous bases that make up RNA. Moreover, scientists were surprised to also find some amino acids.
It is too early to draw conclusions about the origin of life from space
On the one hand, scientists have confirmed that RNA, andmore precisely, their components could have been brought to Earth from space. But not everything is so clear yet. The fact is that scientists studied meteorites that were found on Earth. It means that
nitrogenous bases found on them could be the result of pollution. That is, genetic letters could stick to meteorites after contact with the surface of our planet.
Of course, Japanese scientists have tested this version.To do this, they carefully studied the content of nitrogenous bases on the meteorites themselves, as well as on the soil around them. As a result, it turned out that there are more genetic letters on meteorites than in the soil around them. But this cannot be said about cytosine and uracil.
ATTENTION! The information you need to know is here. On our Yandex.Zen channel you will find content that we do not publish on the site.
But on the meteorites, scientists have foundchemical variants of nitrogenous bases that were not found in the soil. Therefore, it is quite possible that organic isomers can also be cosmic, but, as they say, this is not accurate.
Get an accurate answer, on the one hand, verysimple - you need to explore the fragments of asteroids collected in space. They certainly could not have been polluted from the surface of the Earth. If the presence of nucleic organics on them is confirmed, then it will be possible to assert with confidence that the cosmos is largely involved in the origin of life on Earth.
But, be that as it may, the Earth in any caseunspeakably lucky that the conditions were suitable for the origin of life. After all, she had every chance to forever remain a “steam boiler” with exorbitant temperatures.