All four building blocks of DNA are found in meteorites 2022-04-27 14:20:02



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For the first time ever, all four major components of DNA, the biological blueprint for living organisms, have been discovered in rocks from outer space, a finding that suggests the building blocks of life may have been delivered to Earth by ancient extraterrestrial bodies, accordingly. for a new study.

DNA is a helical structure made up of so-called “nuclear bases” — the compounds adenine, guanine, cytosine, and thymine — that combine in diverse permutations to write the source code for life on Earth, including humans. Although adenine and guanine have been present in meteorites for about 50 years, the presence of cytosine and thymine in these extraterrestrial bodies has remained elusive, despite evidence that the compounds may be present in the primordial interstellar dust that gave rise to our solar system around 4.6 billion. Since years.

Now, scientists led by Yasuhiro Oba, a professor at Hokkaido University, have finally discovered trace amounts of cytosine and thymine in three (carbon-rich) meteorites, a finding that bolsters the idea that extraterrestrial influences “contributed to the genesis characteristics of early life on Earth,” according to for Study published on Tuesday in the magazine Nature Communications.

The two newly discovered nuclear bases belong to a group called pyrimidines, while adenine and guanine are classified as purines. In addition to detecting the remaining compounds within DNA, Uba and colleagues also found traces of another pyrimidine called uracil, which is used by RNA, a simpler molecule of DNA, instead of thymine. Although uracil It was identified in meteorites Before, the discovery of all three pyrimidines in space rocks sheds new light on the puzzling rarity of these nucleobases in meteorites, compared to the purines adenine and guanine.

“The lack of pyrimidine diversity in meteorites remains a mystery since pre-biochemical models and laboratory experiments predicted that these compounds could also be produced from chemical precursors found in meteorites,” Uba’s team said in the study. “Here we report the discovery of nucleoli in three carbonaceous meteorites using the latest improved analytical techniques for the small quantification of nucleoli down to the parts per trillion (ppt) scale.”

“In addition to the purine nucleobases previously discovered in meteorites such as guanine and adenine, we identify several pyrimidine nucleobases such as cytosine, uracil and thymine,” they added. “This study demonstrates that a variety of meteorite bases could serve as building blocks for DNA and RNA on early Earth.”

The team achieved this breakthrough by analyzing samples from the Murchison, Murray, and Tagish Lake meteorites, which landed in Australia, Oklahoma and British Columbia, respectively. The research follows a number of studies related to these meteorites, and others that have been found ProteinsAnd nitrogenAnd waterAnd organic compoundsand other key components of life in extraterrestrial bodies that ended up on Earth, potentially sowing the seeds of habitability on our infant planet.

It is even possible that nascent life forms may have moved between worlds – such as Earth and Mars – through A process known as panspermiawhere organisms are able to survive interplanetary journeys by hiking on meteorites that are slammed by impacts on their home worlds.

While it remains unclear why purines are so easily detected in space rocks, the researchers believe that all of these nuclear bases could have been formed through photochemical processes in the interstellar medium,” indicating that these classes of organic compounds are ubiquitous in the extraterrestrial environments. Inside and outside the solar system,” according to the study.

In other words, the new findings not only help unravel the story of our origins as Earthlings, but may also aid our search for alien life elsewhere in the universe. The rise of sample return missions like NASA’s OSIRIS-REx, which will transport pure material from a carbonaceous asteroid to Earth next year, will limit these basic human questions about how life began on our planet, and whether it exists elsewhere.