The main components of life may have arrived from space – 04/28/2022 – Science

A new analysis of fallen meteorites in the United States, Canada and Australia reinforces the idea that early in Earth’s history, these bodies may have brought biochemical components to the planet for the emergence of life.

In these meteorites, scientists previously discovered three of the five chemical compounds needed to form DNA, the molecule that carries genetic instructions in living organisms, and RNA, the primary molecule controlling the actions of genes. Researchers announced Tuesday that they identified the last two particles after refining the way they analyzed meteorites.

In contrast to what has been done in previous works, the methods used this time were more sensitive and did not involve the use of strong acids or a high-temperature liquid to extract the five components, known as nucleobases. This information is from astrochemist Yasuhiro Oba, of the Institute of Low Temperature Sciences at Hokkaido University in Japan, and lead author of the study published in the specialist journal Nature Communications.

Nuclear bases are nitrogen-containing compounds that are essential in forming the characteristic double helical structure of DNA.

Confirming an extraterrestrial origin from the full set of nuclear bases found in DNA and RNA bolsters the theory that meteorites may have been an important source of the organic compounds needed for the first organisms to appear on Earth, according to astrobiologist and study co-author Danny Glavin of Goddard Space Flight Center. NASA in Maryland.

Scientists are seeking to better understand the events on Earth that allowed different chemical compounds to assemble in a warm aquatic environment to form a living, proliferating microbe. The composition of DNA and RNA may be a key parameter, because these molecules mainly contain the instructions for building and running living things.

“There is still a lot to learn about the chemical steps that led to the emergence of life on Earth – the first self-replicating system,” Glavin said. “This research undoubtedly adds to the list of chemical compounds that may be present in prebiotic broths. [presente antes do surgimento da vida] The beginning of the earth.

The researchers examined material from three meteorites: one that fell in 1950 near Murray, Kentucky, one that fell in 1969 near Murchison in the Australian state of Victoria, and one that fell in 2000 near Tagish Lake, in the Canadian province of British Columbia.

The three meteorites are classified as carbonaceous chondrites, made of rocky material that would have formed early in the history of the solar system. It is rich in carbon. About 2% of the mass of the Murchison and Murray meteorite is made up of organic carbon, while the Tagish Lake meteorite contains 4% of organic carbon. Carbon is one of the basic building blocks of Earth’s organisms.

“The three meteorites contain a very complex mixture of organic molecules, most of which have yet to be identified,” Glavin said.

Earth formed about 4.5 billion years ago. In its early days, it was bombarded with meteors, comets and other material from space. The first organisms on the planet were primitive microbes in primitive seas, and the oldest known fossils are marine microbial samples dating back about 3.5 billion years, although there is evidence of life in ancient fossils.

The two nuclear bases now discovered in meteorites, cytosine and thymine, may not have been detected in previous analyzes because they have a more precise structure than the other three, the researchers said.

The five nuclear bases were not the only chemical compounds necessary for life. Among other things, amino acids, protein components and enzymes are needed. Polysaccharides, which are part of the backbone of DNA and RNA; and fatty acids, which are structural components of all cell membranes.

“The current results may not directly explain the origin of life on Earth, but I believe they could increase our understanding of the list of organic molecules present on Earth early before life appeared,” said Oba.

Translated by Clara Allen

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