DNA Building Blocks May Be Come to Earth on Meteorites

According to NASA researchers some building blocks of DNA, the molecule that carries the genetic instructions for life, found in meteorites were likely created in space. Dr. Michael Callahan of NASA’s Goddard Space Flight Center, Greenbelt, Md. say that for the first time, they have three lines of evidence that together give confidence these DNA building blocks actually were created in space. In the new work, the Goddard team ground  up  samples of  twelve carbon-rich  meteorites,  nine  of  which were  recovered from Antarctica. The team found adenine and guanine, which are components of DNA called nucleobases, as well as hypoxanthine and xanthine. 

Also, in two of the meteorites, the team discovered for the first time trace amounts of   three  molecules related to nucleobases:  purine, 2,6-diaminopurine, and 6,8-diaminopurine, the latter two almost never used in biology. These compounds have the same core molecule as nucleobases but with a structure added or removed. The second piece of evidence involved research to further rule out the possibility of terrestrial contamination as a source of these molecules. Thirdly, the team found these nucleobases both the biological and non-biological ones were produced in a completely non-biological reaction. According to Callahan there seems to be a goldilocks class of meteorite, the so-called CM2 meteorites, where conditions are just right to make more of these molecules.