It may sound strange, but it’s possible that some of the earliest components of life on a meteorite were brought to Earth. Recent research has shown that all five basic building blocks of DNA have been found in meteorites.
To be clear: DNA has not been found on a rock from outer space. Rather, the result is that each of the five basic compounds that make up DNA and RNA, called nucleobases, have been found in meteorite samples. Previously, only three of these nucleobases had been found on meteorites, but recent research has identified the latter two.
Conceptual image of meteoroids supplying nucleobases to the ancient Earth. The nucleobases are represented by structural diagrams with hydrogen atoms as white spheres, carbon as black, nitrogen as blue and oxygen as red. NASA Goddard/CI Lab/Dan Gallagher
“We now have evidence that the complete set of nucleobases used in life today could have been available on Earth when life arose,” said one of the authors, Danny Glavin of NASA’s Goddard Space Flight Center, in a statement.
The two excellent nucleobases were cytosine and thymine. These were more difficult to identify than the other three nucleobases (adenine, guanine and uracil) because they have a more delicate structure that can be easily broken down by the process of collecting and analyzing samples. NASA describes the traditional method of analyzing these samples as making a “meteorite tea,” in which small samples of a meteorite are placed in hot liquid so that the samples are extracted and the aqueous solution can be studied.
“We’re studying these water extracts because they contain the good stuff, ancient organic molecules that could have been important building blocks for the origin of life on Earth,” Glavin explains.
But the two remaining nucleobases required a more careful method to be identified, using cold water and a more sensitive analysis process. “This group has succeeded in using a technique that is more like cold brew than hot tea and is able to extract more delicate compounds,” explains another co-author, Jason Dworkin. “I was surprised that they had seen cytosine, which is very fragile.”
Whether the ingredients for life actually made it to Earth on a meteorite is still an open question. Life could also have evolved from the primordial soup of a very young planet Earth, from the interactions of organic compounds. But this research opens up more possibilities for future research on the subject.
“As a result, more and more pieces are added; Meteorites have now been discovered to contain sugars and bases,” Dworkin said. “It’s exciting to see progress making the fundamental molecules of biology from space.”
The research is published in the journal Nature.