DNA is Hardier Than We Thought

It can survive suborbital spaceflight, but what about longer interplanetary trips?

TEXUS 50 launch.jpg
A TEXUS suborbital rocket launches from the Kiruna range in Sweden.

Astrobiology was in the news recently after a group of researchers led by Cora Thiel from the University of Zurich in Switzerland reported in the journal PLOS One that DNA can survive a short suborbital spaceflight.

DNA had been applied to the exterior of the TEXUS-49 rocket launched in 2011, in protected areas such as the grooves of screw heads. After the rocket landed, the researchers analyzed these areas for surviving biomarkers. To their astonishment they found not only the biomarkers, but the DNA itself—up to 53 percent of the originally applied DNA was still there. Furthermore, up to 35 percent of the DNA was fully functional after a brief exposure to space (the entire mission lasted 20 minutes).

The initial reaction from some scientists was that the finding makes the idea of panspermia—the transfer of life from one planet to the other in space—much more likely, and may have direct implications for the origin of life on Earth.

While the report is intriguing, and suggests that DNA is much more resistant than many of us previously thought, the connection to panspermia theory has to be taken with a grain of salt. First, the DNA applied to the rocket was plasmid DNA, which is a short piece of DNA, like a flash drive for a computer, that provides only a limited amount of information related to adaptation to extreme environments or antibiotic resistance. Chromosomal DNA, which is much longer and has the function of reproduction, is less hardy.

Further, the DNA on TEXUS was not exposed to the full rigors of space, since it reached an altitude of just 268 kilometers, and for only a short period. DNA is most susceptible to damage from radiation, particularly cosmic radiation and ultraviolet radiation, and any DNA traveling from one planet to another would be exposed to the full rigors of space for a very long time, at least thousands of years. If it hitchhiked on a meteorite, it would have to withstand much higher temperatures entering Earth’s atmosphere than it did during a controlled rocket flight. Also, DNA by itself is not life; entire cells would have to survive in order to be able to metabolize and reproduce.

The researchers should be congratulated for trying an “outside-the-box” experiment, which produced a result not many of us would have expected. But I don’t believe it has direct implications for how and where life originated. That probably happened in a little pond or a hydrothermal vent on the surface or just below the surface of our planet, in a place well protected from the harshness of space.