DNA molecules smeared onto the exterior of a sub-orbital test rocket are capable of surviving a 13-minute trip into space and a scorching re-entry, European researchers say.
The scientists' surprising finding, which was published Wednesday in the journal PLOS One, suggests that genetic material is hardier than previously thought and may have the potential to stow away on robotic landers bound for other worlds, or within meteors, the report said.
"It is conceivable that life exists independently from our planet even under the very hostile conditions prevailing on our neighbors like Mars," wrote senior study author Dr. Oliver Ullrich, a molecular biologist at the University of Zurich, and his colleagues.
"Already on Earth we are able to identify some extreme life forms which can survive physically and/or geochemically harsh conditions, such as very high or low temperatures, intense radiation, pressure, vacuum, desiccation, salinity and pH. Many of these parameters also prevail in space and therefore the question is whether terrestrial organisms are able to survive a voyage through space."
The experiment was conducted on the TEXUS-49 rocket mission that blasted off from Sweden in March 2011. The launch was part of a sounding rocket program in which instruments and experiments are launched into sub-orbital space for brief periods.
Researchers engineered plasmid DNA, or small ring-like strings of genetic material, that would confer special qualities to transfected cells, such as making bacteria resistant to certain antibiotics or making mouse tissue cells glow under ultraviolet light.
By engineering the plasmid DNA in this way, they would be able to see whether it was still functional when the rocket returned to Earth.
The researchers applied the DNA to various locations on the exterior of the rocket, including a number of screw heads. During the experimental flight, the material was lofted 166 miles high and subjected to 6.3 G's of thrust, six minutes of microgravity and temperatures higher than 1,832 degrees, the researchers said.
When the rocket payload was recovered, scientists collected some DNA from all of the application sites and found that as much as 35% had retained its full biological function, they said.
The authors said they were very surprised by the results.
The possibility that Earth DNA could contaminate equipment searching for signs of possible life on other planets had to be seriously considered, the authors said.
"It is essential to know whether the detected biomarkers definitely originate from the analyzed site or if they could be potential contaminations from 'stowaways' which traveled as hitchhikers on the spacecraft or analytical equipment."
The researchers said that more tests with biomarkers should be conducted with sounding rockets.
"A critical question is if microorganisms do not only survive the residence in space but would they also be able to withstand the hostile conditions of entering a planet's atmosphere when they are situated e.g. on a meteorite," authors wrote.