The discovery could add weight to the hypothesis that the building blocks of life on Earth originally came from space, but some scientists note the possibility of contamination.
All five nucleobases that make up DNA and RNA have now been detected in meteorite samples, according to a study published yesterday (April 26) in Nature Communications. The work used recently developed techniques to identify not only adenine and guanine—which had previously been identified in samples from some of the same meteorites—but also cytosine, uracil, and thymine, supporting the idea that the precursors of life could have come from space.
The work “provides additional support for the theory that the delivery of these compounds to Earth by meteorites may have played a role in the emergence of genetic functions for early life,” study coauthor Daniel Glavin, an astrobiologist at NASA, which supplied one of three meteorites used in the study, tells Chemistry World.
To see whether nucleobases could form under extraterrestrial conditions, the researchers also ran “laboratory experiments simulating photochemical reactions in the interstellar medium,” Glavin tells Chemistry World. They found that they could make the nucleobases at concentrations similar to those found on the meteorites, he says, “providing additional evidence that nucleobases can be formed in space.”
“It’s very strange to think that the molecules which make up DNA can be found in rocks from space,” Helena Bates, an asteroid researcher at the Natural History Museum in London who was not involved in the work, tells the museum’s news site. “It suggests that these molecules are all over the place, which has a lot of implications when it comes to considering the potential distribution of life within our Solar System.”
However, Michael Callahan, a cosmochemist at Boise State University who was not involved in the work but has collaborated with some of the authors, tells Science News that he thought the study didn’t rule out the possibility that the meteorites were contaminated after reaching Earth, as terrestrial soil and other environments also contain nucleotide bases. “I think [the researchers] positively identified these compounds” in their samples, Callahan says. But “they didn’t present enough compelling data to convince me that they’re truly extraterrestrial.”