Parts of DNA can form in space.
For the first time, scientists have made 2-deoxyribose, the sugar that makes up the backbone of DNA, under cosmic conditions in the lab by blasting ice with radiation. The result, reported December 18 in Nature Communications, suggests that there are several ways for prebiotic chemistry to take place in space, and supports the idea that the stuff of life could have been delivered to Earth from elsewhere.
“It tells us that this process happens everywhere, at least in our galaxy,” says astrochemist Michel Nuevo of NASA’s Ames Research Center in Moffett Field, Calif.
Nuevo and his colleagues cooled ices of frozen water and methanol to about –260° Celsius inside a vacuum chamber and blasted the ice with ultraviolet light, mimicking the conditions found in interstellar clouds. Warming the irradiated ices simulated what happens when a young star is born. After analyzing the ice’s contents, the team identified 2-deoxyribose, as well as several other kinds of sugars made in similar experiments in the past (SN: 4/30/16, p. 18).
Experiments that had made ribose, the sugar of RNA, suggested that the sugars could be built up from reactions involving the simple molecule formaldehyde, which has been found in comets (SN Online: 10/23/14). But those reactions always lead to sugars with more oxygen molecules than deoxyribose has, Nuevo says. “The fact that we made deoxyribose points to another kind of mechanism.”
Nuevo and his colleagues also found simple deoxy sugars in meteorite samples, but not deoxyribose. That could suggest that, although deoxyribose can form in ices that predate stars, the sugar is not stable in the rocks that ultimately form planets.
Two ongoing asteroid missions might be able to help figure out why. Japan’s Hayabusa2 mission (SN Online: 6/27/18) and NASA’s OSIRIS-REx mission (SN Online: 12/10/18) will bring samples back to Earth, where scientists can search them for signs of deoxyribose and other biologically important molecules.