The existence of amino acids outside the earth has been confirmed for the first time. Is the theory of extraterrestrial life true?

According to the Nikkei, the Japan Aerospace Exploration Agency's asteroid probe Hayabusa 2 found amino acids, the "source of life," in sand samples brought back to Earth from the asteroid Ryugu. This is the first time that amino acids have been confirmed to exist outside Earth.

It is undeniable that this is indeed a good discovery, but it is still a little short of inferring extraterrestrial life. Why do I say so? Let's talk about it.

01. How did life originate?

The basic idea is to find out what substances are needed for the simplest life. Basically, up to now, it is generally believed that the most basic substances for life include DNA/RNA, amino acids and other components. Components such as phospholipids that make up the cell membrane are generally believed to have appeared later.

Therefore, how these substances are formed becomes the key to the origin of life.

Going further, we move towards a theory that is closer to the essence: how organic matter was formed. After all, it is generally believed that there was no organic matter in the primitive universe, and inorganic matter must have come first.

Therefore, the conversion of the three most basic chemical substances CO2\N2\H2O, which are considered to be extremely simple, into the basic raw materials of life has become the basis of what everyone believes to be the origin of life.

As shown in the figure below, there are several paths that generate cell membranes (without cell membranes, in an open system, life cannot exist), nucleic acids, and polypeptides [2].

02. Theory of the formation of basic raw materials of life

So, how did these substances form? There are several theories.

1. Primordial Soup

The earliest theory proposed was the "primordial soup" theory, which holds that there was a large amount of inorganic matter on the early Earth, and that the high-temperature discharge process of lightning and thunder easily allowed the inorganic matter to combine into organic matter. As a result, a large amount of organic matter gathered in the Earth's oceans, and these organic matter further formed the raw materials of life, such as DNA/RNA or amino acids, under the action of high temperature and lightning.

Even in the middle of the last century, the famous Uri Miller experiment was conducted, which simulated the process of forming primitive amino acids under the influence of lightning and other factors.

This experiment also became an important foundation for the primordial soup theory.

2. Undersea volcanoes

Of course, later on, people came up with a second theory, which is the submarine volcano theory, which believes that it is easier to synthesize the basic components of life in the high-pressure and high-temperature environment of an submarine volcano.

Furthermore, structures such as sieve holes formed by submarine volcanoes can also play the role of cell membranes and cell walls, used to distinguish different modules, making it more likely to form life [3].

3. Extraterrestrial Origin

Later, it was the origin of extraterrestrial life. The main theory of the origin of extraterrestrial life is still the view of how organic matter was formed, and the discovery of related organic matter in meteorites or samples brought back from extraterrestrial space also provides a basis for this theory.

03. What is the source of life?

At present, the three theories each have their own evidence, but they also have their own flaws. Moreover, whether these organic substances are the basic substances of life needs to be discussed. What is even more, what is the source of life?

Amino acids or nucleic acids? RNA or DNA? If the origin of life must be traced back to the “one”, I prefer RNA! Why?

Because we believe that the origin of life should be a replicator process. And for a single replicator to complete replication, according to our understanding of replication today, there must be two conditions:

1. Sufficient raw materials

2. Catalysis

Especially the second one, if it cannot catalyze, then according to the conditions of biological reactions, it must be a violent organic condition. Even if it is replicated, it will be inactivated quickly under violent conditions. Therefore, it must be mild, so enzymes are needed. Among DNA, RNA and amino acids, only RNA meets this condition.

I wonder if you remember an important discovery, that is, enzymes are not all proteins, because there is an exception, ribozymes, which are RNA, but have enzyme catalysis.

Therefore, we currently believe that in searching for the origin of life, we still have to focus on RNA.

04. The origin of life, many coincidences

Although there are life-generating materials outside the Earth, it is not so easy to really make life form outside the Earth.

A planet can't be too big or too small.

A planet can't be too young or too old.

You can't be too close or too far from a star.

Self-protection is also necessary.

A satellite is also very important.

Under this series of conditions, there are not many places in the Milky Way that meet the requirements, let alone the solar system.

05. The extraterrestrial origin of life

The extraterrestrial origin of life is a new theory developed in recent years and has become an important branch of the origin of life.

The discovery of amino acids in the samples brought back from outer space by Japan's Hayabusa 2 provides new evidence for the theory of extraterrestrial origin of life. Prior to this, another study published in the Proceedings of the National Academy of Sciences found sugar molecules such as ribose and arabinose in three carbonaceous meteorites. Ribose is the basic structure of two other key life substances: DNA and RNA, whose Chinese names are deoxyribonucleic acid and ribonucleic acid respectively [1].

Overall, I think this discovery may provide a more accurate statement: the universe can also provide raw materials for the origin of life on Earth.

[1] Furukawa Y , Chikaraishi Y , Ohkouchi N , et al. Extraterrestrial ribose and other sugars in primitive meteorites[J]. Proceedings of the National Academy of Sciences, 2019, 116(49):201907169.

[2]Norio, Kitadai, Shigenori, et al. Origins of building blocks of life: A review[J]. Geoscience Frontiers, 2018, v.9(04):157-193.

[3]Sean Jordan, Origins of life: new evidence first cells could have formed at the bottom of the ocean, The Conversation 2019.