“Amino acid production in space” approaches Ryugu samples Sorae Portal to space

「Amino acidThey are the basic elements that life is made of. This is because different proteins, which are made by combining many amino acids, play an indispensable role in maintaining life activities, such as cell structure and biological interactions. So where did those amino acids come from ?

Previous studies have considered meteorites containing amino acids as one of the main candidates. Optical isomers of most amino acids. (※) It exists, because the ratios of amino acids in meteorites and those on Earth match well.

Molecules that have the same composition except that they are mirror images are called optical isomers. Life on Earth mainly uses one optical isomer (called the left side), and meteorites are the only extraterrestrial matter known to contain a relatively higher amount of the same optical isomer.

However, it was not yet clear where the amino acids found in asteroids came from, and the origin of many meteorites. Asteroids are thought to be a mixture of materials that underwent slow chemical changes in the cold space environment before the birth of the solar system and materials that underwent chemical changes in the hot environment immediately after the birth of the solar system. Until now, it was not clear in which environment the amino acids synthesized on asteroids were dominant.

A particular problem is that so far this type of research has only been done with meteorites. Meteorites begin to deteriorate as soon as they enter Earth’s atmosphere, and no matter where they fall on Earth full of life, pollution from Earth-derived amino acids cannot be reduced to zero. It is also difficult to determine which asteroid is the parent of a particular meteorite. Because of these circumstances, there was a limit to the extent that could be demonstrated in research aimed at meteorite analysis.

A research team led by Christian Potiszel of Okayama University is using the Japan Aerospace Exploration Agency (JAXA) Asteroid Explorer “Hayabusa 2An asteroid returnedRyuguWe conducted research to determine the origin of the amino acids using samples from

Ryugu is believed to have the same rock quality as a type of meteorite called a “carbonaceous chondrite”. Since carbonaceous chondrites contain many amino acids, it is very likely that asteroids such as Ryugu are the origin of the amino acids on Earth. Also, since the samples Hayabusa2 brought back were directly from the asteroid, the origin is clear, and it was confirmed that there was almost no pollution originating from Earth. For these reasons, Ryugu’s samples are well suited to this type of study.

Ryugu, about 900 meters in diameter, is believed to have been formed by accretion of some fragments of a much larger body. Ryugu’s original body is believed to have formed shortly after the birth of the solar system, but in such an environment, the interior of the mother’s body would have been heated for millions of years to a temperature high enough to melt ice due to a brief heat of decay. Radioactive isotopes lived and believed to be

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In fact, previous research on the Ryugu samples found some minerals that either required liquid water or were more likely to form in the presence of liquid water, and were believed to contain substances that indicated a reaction had occurred.

Similarly for amino acids, traces of chemical reactions involving liquid water can be found. If such traces are found, it can be said that Ryugu’s amino acids were produced in a hot environment just after the birth of the solar system. On the contrary, if no such traces are found, it can be said that the amino acids in Ryugu were produced in a cold environment before the birth of the solar system.

To answer this question, Potiszil and his colleagues analyzed samples collected from each of the Hayabusa2 landings.

As a result, the sample “A0022” (which originated from the surface of Ryugu) was collected during the first containment landing.DimethylglycineIt was found that there is a large amount of amino acid called dimethylglycine is an amino acid that is rare in extraterrestrial material. On the other hand, it was also found that the sample “C0008” (originating from within Ryugu) collected during the second landing contained almost no dimethylglycine.

also ,glycinehigher in C0008 (internal derived) than in A0022 (surface derived).beta alanineHigher in A0022 than in C0008. The types and ratios of amino acids seem to reflect the different chemical changes that each sample undergoes, that is, the different environments.

[▲ الشكل 2: (أ) صورة العينة A0022 (شريط المقياس 500 ميكرومتر = 0.5 مم). (ب) صورة المجهر الإلكتروني المستعرضة لـ A0022. الكربونات والمغنتيت (أكسيد الحديد) والمصفوفة التي يهيمن عليها فيلوسيليكات ، وما إلى ذلك ، هي معادن تتشكل بسهولة بمشاركة الماء السائل (Credit: Potiszil، et.al.)]

We found that these environmental differences can be estimated by comparing the types and proportions of amino acids and non-amino acid minerals present in the samples.

For example, one of the reactions that produces dimethylglycine is the “Eschweiler-Clarke reaction”. In this reaction, glycine, formic acid, and formaldehyde react in water to generate dimethylglycine, producing carbon dioxide as a byproduct. There are several reasons why the Eschweiler-Clarke reaction is so important.

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1. Glycine, formic acid, and formaldehyde are all abundant substances in comets, and they are expected to be abundant in asteroids as well.
2. The fact that the reaction takes place in water, that is, in liquid water, indicates that the ice is melting due to the generation of heat.
3. Carbon dioxide remains as a mineral in the form of carbonate. Minerals that form with the participation of liquid water are also found, such as phyllosilicates and magnetite.

In other words, A0022 is presumably rich in dimethylglycine because it is associated with the experience of an environment where liquid water was present in the past.

These results indicate that the differences in amino acids between the Ryugu samples are due to the different chemical changes that the different samples underwent due to the previous environment. It also shows that evidence of the reactions that produce amino acids is left not only because of the amino acids themselves, but also because of other minerals.

For these reasons, there are avenues for future research. For example, although this research focuses on reactions to produce the amino acids present in the sample, some amino acids must be destroyed during chemical reactions. By also looking at amino acids not present in the sample, we may be able to determine the exact chemical reactions the asteroid has undergone. If this is the case, it is expected that we will be able to obtain clues to more precisely understand the origin of the amino acids that made it to Earth.

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Text: Rare Aya