A new study of meteorites that fell in the United States, Canada and Australia confirms the idea that, at the beginning of Earth’s history, such objects may have supplied life-giving chemicals.
Scientists have previously identified these meteorites with three of the five chemical components needed to form DNA, the molecule that carries genetic instructions in living organisms, and RNA, the molecule that is crucial for controlling the action of genes. Researchers said Tuesday that they have already identified the last two after fine-tuning the way they analyze meteorites.
Unlike previous work, the methods used this time were more sensitive and did not use strong acids or hot liquid to extract the five components known as nucleobases, according to astrochemist Yasuhiro Oba of the Institute of Low Temperature Science at Hokkaido University in Japan. , lead author of the study published in the journal Nature Communications.
Nucleobases are nitrogen-containing compounds that are crucial for the formation of the characteristic structure of double-stranded DNA.
Confirmation of the extraterrestrial origin of the full range of nucleobases found in DNA and RNA supports the theory that meteorites could be an important source of organic compounds needed for the first living organisms on Earth, according to astrobiologist and co-author Danny Glavin of NASA’s Goddard Space Flight Center in Maryland.
A meteorite from Lake Tagish fell in northern British Columbia on January 18, 2000. It produced a remarkable fireball as it flew across the starry sky, which was observed all the way to Whitehorse, Yukon. (Royal Museum of Ontario)
Scientists are trying to better understand the events that took place on Earth, which allowed various chemical compounds to come together in a warm, aquatic environment to form a living microbe capable of reproducing. The formation of DNA and RNA would be an important cornerstone, as these molecules essentially contain instructions for building and managing living organisms.
“We still have a lot to learn about the chemical steps that led to life on Earth, the first self-replicating system,” Glavin said. “This study certainly adds to the list of chemical compounds that would be present in the early prebiotics of the Earth. [existing before the emergence of life] soup. “
Where meteorites were found
Researchers have studied material from three meteorites – one that fell in 1950 near the city of Murray in the US state of Kentucky; one who fell in 1969 near the town of Murchison in the Australian state of Victoria; and one that fell in 2000 near Lake Tagish in BC
On the morning of January 18, 2000, a blue-green orb of fire pierced the sky & crashed into the frozen Lake Tagish, in the NW BC. It was a stony (chondrite) meteorite. A scanning electron microscope image shows framboid (raspberry-like) crystals of magnetite. pic.twitter.com/yy9ReYgpUC
– @ GSC_CGC
All three are classified as carbon chondrites, made of rocky material believed to have formed at the beginning of the history of the solar system. They are rich in carbon, with the Murchison and Murray meteorites containing about two percent organic carbon by weight and the Lake Tagish meteorite containing about four percent organic carbon. Carbon is a major component of Earth’s organisms.
“All three meteorites contain a very complex mixture of organic molecules, most of which have not yet been identified,” Glavin said.
The earth was formed about 4.5 billion years ago. In its infancy, it was thrown by meteorites, comets and other materials from space. The first organisms on the planet were primitive microbes in primordial seas, and the earliest known fossils are marine microbial specimens dating back about 3.5 billion years, although there are hints of life in older fossils.
The 5 key ingredients
The two nucleobases, called cytosine and thymine, recently identified in the meteorites, may have escaped detection in previous studies because they have a more delicate structure than the other three, the researchers said.
– @UlbertaMuseums
The five nucleobases would not be the only chemical compounds needed for life. Other essentials included: amino acids, which are components of proteins and enzymes; sugars that are part of the DNA and RNA of the spine; and fatty acids, which are structural components of cell membranes.
“Current results may not directly elucidate the origins of life on Earth,” Oba said, “but I believe they can improve our understanding of the inventory of organic molecules on early Earth before life began.”
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