For the first time, a complete set of components for creating DNA has been found in meteorites
(ORDO NEWS) — Using a new ultra-precise analysis, scientists from Japan and the US have found a complete set of nitrogenous bases the information units and building blocks of DNA and RNA in samples from three carbonaceous meteorites.
This does not yet prove that full-fledged DNA molecules can be formed on such extraterrestrial objects. But the discovery demonstrates that all the necessary genetic components could have been brought to the early Earth by meteorites, possibly contributing to the origin of life four billion years ago.
All DNA and RNA molecules that carry the information necessary for the normal functioning of every living being on Earth contain only five basic information components called nitrogenous bases.
They belong to two classes of cyclic organic molecules, purines and pyrimidines. Until now, scientists who have been studying extraterrestrial samples since the 1960s have found no more than three of the five basic bases.
However, a new high-precision analysis by a team of researchers from the University of Hokkaido (Japan) and the National Aeronautics and Space Administration (NASA) has identified all five basic base variants, as well as several of their structural isomers.
For analysis, scientists collected samples from three meteorites of the carbonaceous chondrite type – the Murchison meteorite (near the village of Murchison, Australia) and meteorites from Lakes Murray (USA) and Tagish (Canada).
In addition, the authors of the work analyzed soil samples from the site of the Murchison meteorite to better interpret the results and exclude possible contamination of the samples with terrestrial nitrogenous bases during subsequent analysis.
As a result, it was possible to detect the missing and previously elusive pair of pyrimidine bases – cytosine and thymine. The reason they weren’t detected in previous studies is likely due to the finer structure of these nitrogenous bases, which could have broken down when the samples were removed, the scientists said.
In the new work, the researchers improved the technique for extracting nitrogenous bases from meteorite samples, and also used more sensitive analytical methods that made it possible to capture fewer of these molecules.
At the same time, analysis of soil samples from the site of the Murchison meteorite showed that the nitrogenous bases found in the meteorite are precisely of extraterrestrial origin due to their heterogeneous distribution over the meteorite, and also because a number of structural isomers of these organic molecules are absent in soil samples.
Of course, this discovery does not provide a definitive answer to the question of whether life on our planet evolved with help from space or arose exclusively in the so-called primordial prebiotic soup on the early Earth, about four billion years ago.
However, the complete set of basic nitrogenous bases that form the basis of today’s life, as well as a large number of their isomers, gives scientists an extensive list of compounds to conduct laboratory experiments in order to finally understand how life began on the planet.
The analysis also demonstrated the suitability of a new, more efficient method for analyzing meteorite samples, further enhancing the value of the Ryugu and Bennu sample return missions conducted by Japan Aerospace Exploration Agency’s (JAXA) Hayabusa-2 Automatic Interplanetary Station and NASA’s OSIRIS-REx space probe. respectively.
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