Could the blueprint of life have been generated in asteroids?

Using new analysis, scientists have just found the last two of five DNA and RNA information units that had not previously been discovered in meteorite samples. Although it is unlikely that DNA could form in a meteorite, this discovery demonstrates that these genetic parts are available for delivery and could have contributed to the development of educational molecules on early Earth. The discovery, by an international team with NASA researchers, provides further evidence that chemical reactions in asteroids may manufacture some of the ingredients for life, which could have been delivered to ancient Earth through meteorite impacts or may -be dust fall.

All DNA and RNA, which contains the instructions to build and operate every living thing on Earth, contains five informational components, called nucleobases. So far, scientists scouring alien samples have only found three of the five. However, a recent analysis by a team of scientists led by Associate Professor Yasuhiro Oba of Hokkaido University, Hokkaido, Japan has identified the last two nucleobases that have eluded scientists.

Nucleobases belong to classes of organic molecules called purines and pyrimidines, which have a wide variety. However, it remains a mystery why more types have not been discovered in meteorites so far.

“I wonder why purines and pyrimidines are exceptional in that they do not show structural diversity in carbonaceous meteorites unlike other classes of organic compounds such as amino acids and hydrocarbons,” Oba said. , lead author of an article on the research published April 26 in Communication Nature. “Since purines and pyrimidines can be synthesized in extraterrestrial environments, as demonstrated by our own study, one would expect to find a great diversity of these organic molecules in meteorites.”

“We now have evidence that the full set of nucleobases used in life today could have been available on Earth when life first arose,” said Danny Glavin, co-author of the paper at Goddard Space Flight Center. from NASA in Greenbelt, Maryland.

This newly discovered pair of nucleobases, cytosine and thymine, have been elusive in previous analyses, likely due to their more delicate structure, which may have degraded when scientists previously extracted samples. In previous experiments, scientists created a sort of “meteorite tea”, by placing meteorite grains in a hot bath to leave the molecules of the extracted sample in the solution, then analyzed the molecular composition of the alien broth. .

“We study these water extracts because they contain the right stuff, ancient organic molecules that could have been key elements in the origin of life on Earth,” Glavin said.

Due to the fragility of these two nucleobases, the team was initially skeptical of their presence in the samples. But two factors may have contributed to this new finding: First, the team used cold water to extract the compounds instead of hot formic acid, which is highly reactive and could have destroyed these fragile molecules in the samples. previous ones. Second, more sensitive assays were used that could detect smaller amounts of these molecules.

“This group has achieved a technique that is more like cold brewing than hot tea and is able to extract more delicate compounds,” said NASA Goddard co-author Jason Dworkin. “I was amazed that they saw cytosine, which is very fragile.”

The discovery does not provide compelling evidence as to whether life on Earth received help from space or occurred exclusively in the planet’s childhood prebiotic soup. But the set of nucleobases that make up life today, in addition to other molecules found in the sample, give scientists trying to understand early life more compounds to experiment with in the lab.

“It’s adding more and more bits; it’s been found that meteorites now contain sugars and bases,” Dworkin said. “It’s exciting to see progress in making the fundamental molecules of biology from space.”

Not only has this analysis been added to the kit for those modeling the beginning of life on Earth, but it also provides proof of concept for a more efficient technique for extracting information from asteroids in the future, by particularly samples from Bennu which are heading to Earth next year via NASA’s OSIRIS-REx mission.