For the first time, scientists discover all the necessary ingredients for DNA in a meteorite. Could the main ingredients for life on Earth come from space?
DNA, a molecule that carries the genetic instructions of all living things on Earth; and RNA, a crucial molecule for controlling the actions of genes, contains five informational components. These are called nucleobases.
Until now, scientists analyzing alien samples had found only three of the five. A recent analysis of meteorites that have fallen in the United States, Canada and Australia, has identified the last two nucleobases. It was possible after refining the way they analyzed meteorites.
The new research bolsters the idea that these objects may have been brought to Earth chemical ingredients vital to the appearance of life.
DNA components discovered with a more sensitive analysis method
Unlike previous work, the methods used this time around 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 Sciences at Hokkaido University (Japan). Lead author of the study published in the journal Nature Communications.
Nucleobases are nitrogen-containing compounds that are crucial for forming the characteristic double helix structure of DNA.
How did life begin? While we don’t know exactly, scientists found the last 2 of the 5 informative units of DNA and RNA yet to be discovered in meteorites, providing evidence that chemical reactions in asteroids can make some of the ingredients of life. https://t.co/GnFRcJpvgW pic.twitter.com/4C7MqfmQ9K
— NASA Goddard (@NASAGoddard) April 27, 2022
The confirmation of the extraterrestrial origin of a complete set of nucleobases, found in DNA and RNA, strengthens the theory that meteorites could be an important source of organic compounds necessary for the appearance of the first living organisms on Earth. So says astrobiologist and study co-author Danny Glavin, of NASA’s Goddard Space Flight Center in Maryland.
How would you contribute to this theory?
Scientists have tried to better understand events on Earth. Making different chemical compounds 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 milestone, as these molecules essentially contain the instructions for building and running living organisms.
†There is still much to learn about the chemical steps that led to the emergence of life on Earth. The first self-replicating system,” Glavin said. “This research certainly adds to the list of chemical compounds that would have been present in the prebiotic soup (which existed before the appearance of life) on early Earth.”
DNA material in three meteorites
The researchers examined material from three meteorites: one that fell in 1950 near the town of Murray, Kentucky. Another that fell in 1969 near the city of Murchison, in the Australian state of Victoria. And another that fell in 2000 near Tagish Lake, in the Canadian province of British Columbia.
All three are classified as “carbonaceous chondrites,” made up of rocky material believed to have formed in the early years of the solar system. They are rich in carbon: the Murchison and Murray meteorites contain about 2% organic carbon by weight. While the Tagish Lake meteorite contains about 4% organic carbon. Carbon is a main component of the organisms on Earth.
“All three meteorites contain a very complex mixture of organic molecules, most of which have not yet been identified,” Glavin said.
Primitive microbes in the primeval seas
The Earth was formed about 4.5 billion years ago. In his youth he was struck by meteorites, comets and other material from space. The first organisms on the planet were primitive microbes in the primeval seas. So the earliest known fossils are marine microbial specimens dating to about 3.5 billion years ago, although there is evidence of life in older fossils.
The two nucleobases, called cytosine and thymine, recently identified in meteorites may have escaped detection in previous studies. This is because they have a more delicate structure than the other three, the researchers said.
The five nucleobases would not be the only chemical compounds necessary for life. Among other necessary elements were: amino acids, which are components of proteins and enzymes; sugars, which are part of the backbone of DNA and RNA; and fatty acids, which are structural components of cell membranes.
“Current results may not directly explain the origin of life on Earth”said Oba. “But I think they could improve our understanding of the inventory of organic molecules on early Earth before the start of life.”