The asteroid sample brings back to the outside world "the source of life"?

Recently, the Bird 2 team announced that a variety of amino acids were found in the asteroid dragon palace samples recovered by the detector [1]. This discovery has not yet been officially published in the paper, and it has quickly triggered the media reports and the public's thoughts on exterior life.

What is the special thing about amino acids in life? What amino acids did Bird 2 discovered this time? Is amino acid rare on the planet outside the ground? What does it mean to discover the exterior amino acid? How far is it from amino acids to extraterrestrial life?

Aminoic acid: "Bookstone" of the Carbon -based Life Building

Liquid water and organic matter are the substances necessary for the birth and prosperity of our earth carbon -based life. As a result, whether water and organic matter on a planet has naturally become an important reference basis for our other planets in the universe.

But in fact, the results of deep space detection in recent decades have clearly told us: water is not uncommon. There are many forms of water on the moon, Mars and many asteroids [2-4]; under the ice satellite ice layer of Jupiter and Saturn in the outer solar system, there is a vast liquid water ocean and even the energy supply of deep-sea hot springs. The system is the key goal of looking for out -of -life life to find out -of -space detection tasks.

The eruption of feathers near the Erwei Erda Polar, Cassini detector shooting | NASA/JPL-CALTECH

These intermittent spring-like feathers contain water ice and water vapor, indicating that under the ice layer, liquid water ocean | Sinicization: NASA/JPL-CALTECH

Organic objects are not uncommon.

Comet and small asteroids represented by carbonic asteroids (small planets C planets) are no shortage of organic matter on the stars; Curious Martian carts are clearly sampled by drilling on Mars, and a variety of pneumatic (C4H4S) and aromatic clan have been detected. , Dippermia complicated organic matter [5].

Curiosity sample analyzer (SAM) found a variety of complex organic objects in the thermal decomposition of Mars | References [5]

So why have we not found any life on other planets so far? Are these organic objects "not enough"?

Looking back on our own, the operation of the complex system of the earth requires a "special" organic matter -amino acid.

The basic structure of amino acids is not complicated, including carbon (C), hydrogen (-H), amino (-NH2), carboxyl (-COOH), and an arbitrary side chain group (-R). Obviously, even different-R groups can have a variety of amino acids.

Basic structure of amino acids | Author drawing

Multiple amino acids can be tandem into peptide chains like chain beads; long peptide chains can be further folded and combined together, which can form a variety of protein.

Various amino acids series into peptide chains ｜ Adapted from Wikichomy

However, for the life of the earth, although there are hundreds of amino acids in nature, there are usually only 20 amino acids used to form proteins. This is the so -called "20 basic amino acids" or "proteinogenic amino access".

Other amino acids are not useless to life. Some of them can participate in the operation of the "Life Factory" in the form of short peptide chain (small peptide).

20 basic amino acids that form a protein. There are two kinds of uncommon protein amino acids: selenium cysteine ​​and pyrine lysine, so there will be 22 species of protein amino acids in some occasions | Author drawing

In other words, amino acids are the basic units of protein, and are the "masonry" of the "carbon -based life" building.

Amino acid- "Life Block" | Adapted from pixabay

What amino acids did Bird 2 discovered?

Briefly introduce the new reader to the 2nd: JAXA Bird No. 2 detector was launched in December 2014 and arrived at the target in June 2018 — the near -ground asteroid Dragon Palace.

Bird No. 2 and Small Star Dragon Palace Art Picture | Akihiro Ikeshita/JAXA

From 2018-2019, No. 2 of Bird launched a series of accompanying remote sensing detection and dropping one lander and 3 inspectors on Dragon Palace. It was collected by the asteroid surface and deep underground material through two landing samples.

Bird No. 2 Full Records ｜ Adapted from: JAXA

On December 6, 2020, the Bird No. 2 successfully sent the return compartment of the asteroid sample back to the earth, and then moved to the next detection target -about 30 meters in diameter and rapid rotation 1998 KY26 (planned to 2031 7 Arrive in the month).

Staff recycled the Bird No. 2 sample return compartment in the Woodura test site in Australia | JAXA

Bird No. 2 originally planned to recover 100 mg of small asteroid dragon palace samples, but the actual "out of the box" weighed results showed that a total of 5.4 grams was recovered, which was more than 50 times the planned sampling volume.

The newly discovered amino acids are from the sample particles numbered a0106. This is part of the dragon palace surface sample collected by the No. 2 landing.

Two sample samples in Bird 2 are allocated in two cabins A and C. The picture shows some part of the dragon palace sample granular photos collected in the cab and C rooms in cabin A and C rooms | References [6]

As mentioned at the beginning, this discovery has not yet been organized as a dissertation. It is only published at this year's Moon and Planet Science Conference (LPSC). Make a brief introduction. The study was led by Professor Nara Okiho, the University of Kyushu, Japan, and the Bird No. 2 sample analysis team was completed. Abstract points out: carbon (3.76WT%), hydrogen (1.14WT%), nitrogen (0.16WT%) in A0106 samples are higher than all known carbon ball meteorite (WT is quality percentage); in A0106 samples In the hot hydrolysis extract, more than 10 amino acids were found, including both protein amino acids (such as glycine, α-alanine), as well as non-protein amino acids (such as β-alanine, α-aminoocyte). (PS: The actual observation data and description are subject to the formal published in the future)

The foundation amino acid on the asteroid really means that compared to the discovery of other "ordinary" organic matter, we are a little closer to life.

But the significance discovered this time is not "the first discovery of amino acids." After all ... this is no longer "the first time" to find amino acids on the planet outside the ground.

Amino acids on the planet on the planet

Since the 1970s, people have discovered evidence of amino acids on many planets on the planets, and they have continuously questioned and tested these evidence.

As early as the Apollo era, scientists found some amino acids in the Apollo moon samples, including glycine, alanine, glutamic acid, citineine, aspartic acid, aswaline, and souine. ppb = one -one -one -one -in -one) [7].

Apollo No. 17 astronaut sampling | NASA

However, the process of sample collection, storage, and analysis of samples more than 50 years ago was much rough than now. For example, some samples in Apollo 15, 16, and 17 were stored in the same laboratory with two plans of pure olive rocks in the same time. Essence

However, amino acids can also judge the source of the source through the "chirality" characteristics in the molecular structure: the amino acids except glycine (-R group are H) have L (left-hand) and D-type (left-handed) and D-type (type D) (left hand) (left-handed) (left-hand) (left-handed) and D type (type D) Right -handed) Two heterogeneous, their molecular formulas are the same, and the structure is symmetrical, just like our left hand and right hand, it seems exactly the same, but it can never be rejuvenated by rotation.

One -opponent isomer amino acid ｜ NASA

The amino acids of nature on the earth are mainly L (left -handed) amino acids; the protein in the earth's life, in addition to glycine, is all composed of L -type amino acids. There is no type D (but some small peptides may contain both L. Amino acids also contain D -type amino acids). The amino acids from outside and non -biological are usually the ratio of D -type and L types. This feature is also called "external anti -rotation".

In a re-analysis of amino acids in Apollo samples published in 2016 [8], more types of amino acids (such as glycine, DL-Alanine, DL-Castricine, DL-glutamic acid , DL-serumine, L-Suspenamine, and L-cypamate, as well as some amino acids that were not found in the moon samples before, such as α-amin amino isotonic acid, DL-β-amino ondex, DL-α -Minomolin, γ-amino orthopedic acid, β-alanine, and ε-amino acidic acid, etc.), of which L-type protein amino acids are significantly more than the corresponding D amino acid, indicating that in Apollo Moon samples Protein amino acids are likely to come from pollution of the earth. However, the proportion of Alanine and β-amino-based β-amino-based b-type in the sample is equivalent, indicating that certain amino acids may still come from outside the earth.

There are more amino acids found in meteorites, especially in the meteorites of carbon balls. This type of meteorite is considered fragments from the C -type asteroid (Dragon Palace is a small planet C), and it has not experienced any hot and deteriorated process -that is, this type of meteorite is very old, which may reflect the original material component of the small asteroid of the maternal asteroid star Essence

The meteorite ball grains in the carbon gallery meteorite (Allene Meteorite) slices | Shiny Things / Flickr

The most typical example may be Murchison Meteorite. In 1969, the carbon -gallery meteorites with more than 100 kg of carbon balls fell in the town of Minda, Victoria, Australia. "polluted.

Part of the Merchson meteorite exhibited by the National Natural History Museum | Basilicofresco

In 1970, scientists found 5 kinds of protein amino acids (glycine, alanine, alanine, proline, and glutamic acid) and two non-protein amino acids (N-methadine and α- Athotic acid) [9], another 1 kind of protein amino acid (citizen) and 6 non-protein amino acids (β-alanine, α-amino p-bore acid, β-amino orthopedic acid bore acid (β-alanine) and 6 non-protein amino acids were continued in 1971. , Γ-amino orthopedic acid, isotic acid, and 哌 哌 、) [10]. (PS: In the analysis of Merchissen meteorites published in 2010, more than 70 amino acids were found, which was later talked [11].) In 1971 Methods analyzed another carbon gallery meteorites that were almost contaminated by the earth, Murray Meteorite, and found 6 kinds of protein amino acids (glycine, alanine, sorrericine, milk ammonia Acids, citizes, and glutamic acids) and 11 kinds of non-protein amino acids (isopionic acid, α-aminobutyric acid, N-methadine, α-amino ionic acid, N-methadine -Thiel glycine, nominicine, β-aminotomoic acid, cyposterine, β-alanine, and γ-aminocytic acid) [12].

A small piece of Murray meteorite | University of New Mexico

More importantly, the proportion of type D -type D -type D -type D -type and L types in Mindson and Murray meteorite samples, indicating that these amino acids are likely to come from non -biological sources outside the earth; The types are found in Murray meteorites, which may mean that certain amino acid categories are common in carbon ball meteorite and their mother's asteroids.

Of course, no matter how fast the meteorite is found after landing, it cannot absolutely exclude the possibility of being polluted by organic matter. In contrast, it is obviously more convincing to detect directly on the planet on the ground, or with more advanced sampling techniques recovered from the alien.

In 2016, scientists used the Rosina mass spectrometer of the Rosita detector to detect volatile glycine on the comet 67p/Chulumov [13].

Rosina-DFMS mass spectrometer (left) of Rosina-DFMS and comet 67P image (right) taken by Rossea | ESA

This is the comet component directly obtained by the detector through remote sensing. In theory, there is no possibility of being polluted by the earth's material. This also confirms that the glycine found in the comet sample recovered by the scientist more than ten years ago [14] may not be polluting the earth, but it really exists on the comet 81P/Wilder.

Rosina-DFMS mass spectrometer (NH2‐CH2‐Cooh) ｜ References [13]

After all, glycine is the simplest amino acid. Is there a more complicated amino acid on the planet on the planet?

The analysis of the sample of the Bird has taken another step. As the detection and sampling journey of the first machine of the bird's first machine, the samples brought back from the near -earth asteroid Kawagawa were also contaminated by a small amount of earth, but scientists still detected some uncommon non -protein amino acids on the planet. For example, β-alanine and trace β-aminobutyric acid, β-amino pinkyl, and the latter two are externally anti-rotation mixtures, which are in line with the characteristics of non-biological sources in the ground [15].

Bird and asteroid 艺 艺 | Akihiro Ikeshita/Jaxa

However, Kawagawa is a small (silicon) asteroid. It was not an organic asteroid type, and no reliable external protein amino acid was found.

In contrast, the sample reliability brought back from the C -type asteroid dragon palace this time is higher, and there are more amino acids found from it, and it is clearly found that protein amino acids from outside the ground are found.

This is also the first time that human beings have confirmed to find protein amino acids in samples recovered outside the ground. (You see, as long as there are enough attributives, this "first" can always be obtained

)

Will the amino acids discovered on the 2nd of Bird 2 will be polluting the earth? The possibility is very low.

On the one hand, the samples of the No. 2 of Bird 2 are very successful, the samples are intact, and there is no sample pollution incident in the whole process. After the sample recycling, it has been in a state of strictness from the earth's material, and has never been exposed to the earth's air [6].

On the other hand, all the extraction processes of this sample analysis are carried out on the ISO5 (level 100) cleaning platform in the ISO6 (level 1000) clean room. All the glass utensils used in the study are 500 ° C before contacting the sample at 500 ° C. Bake in the air for 3 hours to avoid possible organic pollutant samples in the container [1].

Coupled with the amino acids detected this time, the samples in the samples are mixed with exterior and the corresponding D -type amino acid ratio is about 1: 1). It can be regarded as an external amino acid real hammer Plus.

However, compared to this "first" that you need to add to get this "first", the more important significance of the 2nd discovery of Octopus 2 is to prove it to us-

Don't deny it anymore. Like water and other organic objects, amino acids are not uncommon on earth planets.

If we agree that the form of life outside the earth is still carbon -based life, and amino acids are also the "key building blocks" that constitute an alien "Life Building", then we have to admit that having a "life block" The threshold is very high. Just as the Miller-Yuri experiment 70 years ago.

In 1952, in the basement of the Chemical Building of the University of Chicago in the United States, Stanley Miller did an experiment under the guidance of the instructor Harold Yuri [16]: They injected some water in the spherical glass container to simulate the ocean. Heat the glass container to simulate the sun, use water, methane, ammonia, and hydrogen to form a "atmosphere" (this is the most likely component of the early atmosphere of the earth at the time), and use electric sparks to simulate lightning.

A week later, the water in the container became reddish brown, and at least 5 amino acids were detected in the solution: glycine, α-alanine, β-alanine, citizen, and alpha-amino acid, and other Complex organic matter.

Miller-Yuri Experimental Design Significance ｜ Tu Sinicates from Carny/Hebrew

In the next 70 years, many scientists either reproduced or improved this experiment. As a result, they all confirmed without exception. It is possible to produce a variety of complex organic matter including amino acids.

Then we have returned to this key question: If there are a big planet hand in the universe holding "life blocks", why have we not found any traces of extraterrestrial life so far?

Fermi Paradox: Where are they all?

One day in 1950, in a group of physicists' chat on extraterrestrial life, Erco Fermi thought: Since there are so many planets in the universe, these planets have such a long time to evolve life or even civilization. Then In terms of probability, extraterrestrial civilizations should have been spread all over the universe.

Then he asked a question: Where are they all?

Why have we not detected any extraterrestrial civilization so far, and there have never been overseas civilization to find us?

With the astronomical discovery of the next decades, this paradox has become more and more thoughtful.

On the one hand, Miller-Yuri experiments and complex organic molecules discovered on the planet outside the ground told us that it is not difficult and rare to produce amino acids on the planet or even more complex organic matter;

On the other hand, with the investors such as the Cairple Telescope and TESS satellite, people have discovered more than 5,000 various exterior planet systems, and this number is still growing rapidly.

If the road to the earth's life and evolution is not a special case, then we may really believe that there are always probability of outbound life or even civilization in the universe.

If there are no other planets born, why is our earth so special? What is the key to the birth of life?

It is true that having "masonry" does not mean that the "house" can be created. Then the real life origin problem may not be how to produce masonry of life, but how to assemble these bricks into a life building.

What will be the next key evidence we look for on the planet outside the earth? Is DNA and RNA carrying effective genetic information? Is it the wreckage or metabolic product of a simple life like microorganism? Until now, we have no answer yet.

But it is certain that we are still hopeful today, and we are still sending detectors to find evidence of life existence (over) on "livable satellites" such as Mars and Jupiter and Saturn ice satellite.

Jupiter and Saturn satellite detectors planned for the next 10 years are mainly to detect livable life and find traces of life. my country's Jupiter Satellite Exploration Mission Tianwen No. 4 is also prepared | ESA / NASA

Whether or not you can find life, in the next decade, we will have a deeper understanding of the life and livable environment in the solar system.

Thank you

This article thanks to the review of Lotte Huang and Teacher Xiaoyu, and I thank you friends Pan Pan, Dafeng, and Liang Hao for their help to improve this article.

references

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Author: haibaraemily

Edit: STEED

Cover Map Source: Adapted from JAXA

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Edit: Zhao Yang

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