Together, DNA and RNA have five informational units that spell out the language of life, or at least life on Earth. Previously, three of these five have been found in meteorites. Researchers have now discovered the last two remaining informational units. This means that the chemicals that make up life on Earth could have possibly come from off the planet.
The informational units, technically called nucleobases, are all part of two types of organic compounds – pyrimidines or purines. Professor Yasuhiro Oba of Hokkaido University led the team that finally discovered the last two nucleobases. He questioned why it took so long to find them in the first place.
“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,” said Oba. “Since purines and pyrimidines can be synthesized in extraterrestrial environments, as has been demonstrated by our own study, one would expect to find a wide diversity of these organic molecules in meteorites.”
“We now have evidence that the complete set of nucleobases used in life today could have been available on Earth when life emerged,” said study co-author Danny Glavin of the NASA Goddard Space Flight Center.
The newly found nucleobases thymine and cytosine have probably been missed so far because they’re quite fragile. In other studies, meteorite pieces have been put into hot water to extract the chemicals to then analyze them.
“We study these water extracts since they contain the good stuff, ancient organic molecules that could have been key building blocks for the origin of life on Earth,” said Glavin.
“This group has managed a technique that is more like cold brew than hot tea and is able to pull out more delicate compounds,” said study co-author Jason Dworkin. “I was amazed that they had seen cytosine, which is very fragile.”
This new study shows that life could be widespread across the universe and that the building blocks of this life could be introduced from space.
The research is published in the journal Nature Communications.