Plasmid DNA attached to the outer surface of a sounding rocket may be able to withstand rocket launch, a period of residence in suborbital space, re-entry, and landing conditions into the Earth's atmosphere, all the while staying intact and active in its function as carrier of genetic information, according to a study published in the open-access journal PLOS ONE by Cora Thiel and Oliver Ullrich from University of Zurich and colleagues.

DNA plays an important role as a biomarker for the search of extraterrestrial signatures of life, and scientists are working to characterize and compare the influence of Earth and space conditions on DNA. The authors of this study designed a test to analyze the biological effects of suborbital spaceflights using the TEXUS-49 rocket mission in March 2011.

They attached artificial plasmid DNA carrying a fluorescent marker and an antibiotic resistance gene cassette at three different positions on the rocket exterior, where outer gas temperatures were estimated at over 1000 C during the short 780 second flight.

Researchers analyzed the samples immediately after the flight, and the results showed that DNA survives to varying degrees in all cases, and in particular, even after application of temporary heating up to 1000 C.

Subsequent analyses showed that DNA could be recovered from all application sites on the exterior of the rocket, with a maximum of 53% in the grooves of the screw heads. Up to 35% of DNA retained its full biological function, as shown by its ability to successfully confer antibiotic resistance to bacteria, and to drive expression of a fluorescent marker in eukaryotic cells.

The authors suggest this experimental design may establish a robust and universal functionality assay to test for the stability of DNA during an atmospheric transit and re-entry, as well as a model for nucleic acids that could serve as biomarkers in the search for past or present extraterrestrial life.

Prof. Ullrich and Dr. Thiel added: "We were totally surprised. Originally, we designed this experiment as a technology test for biomarker stability during spaceflight and re-entry.

"We never expected to recover so many intact and functional active DNA. But it is not only an issue from space to Earth, it is also an issue from Earth to space and to other planets: Our findings made us a little bit worried about the probability of contaminating space crafts, landers and landing sites with DNA from Earth."

Thiel CS, Tauber S, Schutte A, Schmitz B, Nuesse H, et al. (2014) Functional Activity of Plasmid DNA after Entry into the Atmosphere of Earth Investigated by a New Biomarker Stability Assay for Ballistic Spaceflight Experiments. PLoS ONE 9(11): e112979. doi:10.1371/journal.pone.0112979