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On Monday, an article announcing that the four bases of DNA had been found on an asteroid generated many headlines. But many of the headlines omitted a key word necessary to put the discovery in context: “again.” The article itself cites similar results dating back to 2011, and the following years have seen several confirmations and more rigorous studies. The new work was notable less for showing that we had found these bases on Ryugu than for solving a previous mystery: Previous studies had failed to detect them there, despite their presence in many other asteroid samples.
Beyond the headlines, however, the new work provides some interesting details, as it may answer an important question: how these bases got there in the first place. Understanding this better may be critical to getting a better idea of how the raw materials for life ended up on Earth in the first place.
looking for bases
Let’s start with a description of what the researchers found. Both DNA and RNA, the two nucleic acids used by life, share a similar structure. That includes the backbone, a chain alternating between sugars and phosphates that are all chemically linked. While the specific sugar differs between DNA and RNA, the chain itself varies only in length; Otherwise, the backbone of each DNA or RNA molecule is identical.
