Life may not have originated on Earth

It has long been the consensus of the scientific community that modern life on Earth evolved from the first life on Earth over a long period, but the scientific community has no definite answer to the question of "where did the first life on Earth come from?

For the origin of life on Earth, there are two main views in the scientific community. The first view is that life should originate from the Earth and evolve gradually from a series of complex chemical processes in a specific environment of the Earth's "local" inorganic materials.

The second view is that life may not have originated on Earth, but that some small objects in outer space (e.g., comets and asteroids) may have carried with them the complex organic matter that constitutes life, and that when these small objects were captured by Earth's gravity and fell to Earth's surface, the material they carried may have evolved on Earth.

The second idea is more easily verified because "small bodies falling to the Earth's surface" happens all the time on Earth, and we can still find the remains of small bodies - meteorites - on Earth from time to time.

In the past, scientists have been working on the study of meteorites, and as the research continues, there is more and more evidence that life should originate from outer space. The first is that scientists have found that in many meteorite samples, in addition to the presence of more complex organic substances such as alcohols, sugars, and amino acids, there are also bases (Nucleobase), which are important substances that makeup life.

Bases are composed of elements such as carbon (C), nitrogen (N), and hydrogen (H). There are five bases in living organisms on Earth, including adenine, cytosine, guanine, thymine, and uracil, which are capable of forming base pairs and stacking on top of each other, and are These bases form base pairs and stack on top of each other, and are essential for the composition of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in living organisms.

In the 20th century, scientists have discovered adenine, guanine, and uracil in meteorite samples, but the other two bases were not discovered due to the limitation of detection technology. The research did not stop in the 21st century, and with the help of increasingly advanced detection technology, scientists made a major discovery in 2020 - a protein.

The research came from a team led by Harvard astrophysicist Malcolm McGeoch, and the samples were taken from a meteorite named "Acer 086", which was found in the Sahara desert in 1990.

In their work, the researchers used advanced mass spectrometry techniques, which revealed the presence of a protein composed primarily of glycine and hydroxylysine amino acids in the meteorite sample, the general structure of which is shown below (note: the white, orange, gray, blue, red and green spheres in the diagram represent hydrogen, lithium, carbon, nitrogen, oxygen, and iron, respectively).

I believe we all know how important proteins are to life. It is no exaggeration to say that all known life on Earth needs proteins, and without this substance, life on Earth would not be possible, and the discovery of this complex organic macromolecular structure in meteorites is as significant as can be imagined.

By April 2022, the field of related research received another piece of good news: scientists discovered two bases in meteorites that had never been found before - cytosine and thymine.

The research comes from a team led by astrochemist Yasuhiro Oba of Hokkaido University, whose samples were taken from three meteorites: the Murray meteorite (discovered in 1950 in Kentucky, USA), the "Murchison meteorite" (discovered in 1969 in Victoria, Australia), the "The Tagish Lake meteorite (found in British Columbia, Canada, in 2000).

Using a technique known as high-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (HPLC/ESI-HRMS), researchers found a variety of bases and their structural isomers in the meteorite samples, including cytosine and thymine, which means that all five of the bases found in living organisms on Earth have been found in meteorites. This means that all five bases of life on Earth have been found in meteorites.

Among the many small bodies in outer space, very few have fallen to the Earth's surface to form meteorites and have been found by humans, but in these meteorites, there are all kinds of organic materials, including proteins and the five bases needed for DNA and RNA, which indicates that complex organic materials for life are common in small bodies.

Scientists speculate that between 3.8 and 4.1 billion years ago, several rocky planets in the inner solar system (including Mercury, Venus, Earth, Mars, and the Moon) were "intensively bombarded" by small bodies (also known as the "late heavy bombardment period"), during which During this period, a large number of small bodies brought a variety of organic materials to Earth, thus providing an important material basis for the emergence of life on Earth.

In conclusion, although the scientific community is still unable to give a definitive answer to the origin of life on Earth, there is growing evidence that the first life on Earth may not have originated on Earth, but should have originated in outer space. It is conceivable that if this is the case, then life should be widespread in the universe; after all, there are many, many more planets like Earth in the universe.