There are thousands of living species on the earth, where did these species first come from and when did they appear? How did it come about? In fact, it is still a mystery to be solved, but a blockbuster article just published in the authoritative academic journal Nature Communications on April 27 this year revealed that life on Earth is likely to come from outer space as early as possible.
The authors of the article, written by Yasuhiro Oba and colleagues at Hokkaido University and the Japan Marine Science and Technology Center, discovered the two main chemical components of DNA — pyrimidine and purine — through the study of meteorites that fell to Earth in space, and these two nuclear bases are the chemical components that make up DNA that were finally discovered from meteorites.
Pyrimidine is an alkaline nitrogen-containing heterocyclic compound, in the formation of DNA and RNA of the five bases, there are three are derivatives of pyrimidine, namely cytosine, thymine, uracil, of which thymine can only appear in DNA, uracil can only appear in ribonucleic acid, and cytosine can be both, indicating that this substance and life formation have a great relationship.
Purine is a heterocyclic aromatic organic compound, which is a product of the metabolic process of life, including guanine and adenine. When the bases are complementary, thymine (in DNA) or uracil (in RNA) and adenine can bind with 2 hydrogen bonds, and cytosine and guanine can bind with 3 hydrogen bonds, which also shows that they are important substances for compiling the code of life.
Yasuhiro Oba and his colleagues discovered these materials in meteorites, focusing on three carbon-rich meteorites using small-scale quantification techniques optimized for bases: the Murchison meteorite, the Murray meteorite, and the Tagish Lake meteorite.
Murchison meteorite
The Murchison meteorite fell on September 28, 1969 in the Murchison region of Victoria, Australia, the Murray meteorite was a meteorite that fell in Murray, Arkansas, usa, in 1952, and the Tagish Lake meteorite fell on January 18, 2000 in the Lake Tagish region of northwestern British Columbia, Canada. They found more than 70 kinds of amino acids in the Murchison meteorite alone, including common glycine, alanine, glutamic acid and the like, as well as substances such as isovaramine and salionine that are not easy to find, as well as different functional groups such as dicarboxyl and diamino, in January 2020, scientists published a paper saying that through the determination of the silicon carbide particles carried by the meteorite, it was found that it has a history of 7 billion years, which is not only earlier than the formation time of the earth, but even earlier than the formation of the solar system. The Murray meteorite is also older than Earth, and it has also found different DNA components from the Tagish Lake meteorite.
These new research results that have just emerged in recent years are likely to be revealing a secret, that is, the original source of life on Earth is likely to come from outer space, even before the formation of the solar system, there was already life, but life existed on other planets, and later in a natural disaster, these traces of life became asteroids drifting in space, some of which fell to Earth as meteorites, and were not discovered by scientists until today.
However, there is another possibility, that is, the DNA molecules or molecular strands that make up life can form in their natural state and then be absorbed by some asteroids, or they may form on a certain planet, but the planet is later broken by the impact, leaving some DNA fragments on the asteroid.
The traditional concept is that the formation and evolution of life are extremely complex, only the probability of protein amino acids synthesized in nature, just like the parts of a car are all disassembled and thrown into the air and automatically assembled into a car, but now through the study of THE composition of DNA, RNA, etc., it is not difficult to form many molecular chains in nature, and it is not so difficult to mix a large number of molecular chains together to create more complex DNA, RNA, etc. Some scientists have found pyrimidine in experiments simulating the formation conditions of the interstellar medium, which also shows that some organic molecules can be synthesized naturally in the universe and even in extremely cold interstellar space.
Scientists also believe that dna and RNA fragments in the meteorite to the earth, in the atmosphere and the ground impact process, the high temperature state will also contribute to the synthesis of some of the material needed for life, so whether life formed on earth or from outer space, is still a mystery. However, since life can be formed on Earth, then those planets in the universe with similar conditions to Earth should not be an exception.
Resources:
"China News Network" April 27 article "The latest international study found the main components of DNA in meteorites or brought to earth by meteorites"
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