In something that only seems possible in a sci-fi movie, imagine scientists discovering life on another planet only to learn that the extraterrestrial life originated on Earth. New research suggests that life spreading planet to planet from space bodies contaminated with human DNA, or other earthly living objects, is possible.
First sea plankton were found living on the exterior of the International Space Station, now scientists have discovered that it is possible for DNA samples to survive at least a short space ride on the exterior of a rocket.
A new study published in PLOS One reports that DNA squirted onto the exterior of a TEXUS-49 sounding rocket remained functional following a 13-minute low-orbit flight to space. The lead author on the DNA study, and molecular biologist at University of Zurich, Cora Thiel, noted that findings were not expected and "made us a little bit worried."
"We were totally surprised…We never expected to recover so many intact and functional active DNA. Our findings made us a little bit worried about the probability of contaminating space crafts, landers and landing sites with DNA from Earth."
The research happened by chance. The researchers intended to examine the effect of gravity on DNA. The experiment was placed inside the cargo bay of the rocket. However, during flight preparations the researchers decided to put some DNA on the exterior of the rocket as well: around the outside of the payload, in the grooves of the screw heads, and underneath the payload. Their intention was to test the robustness of a biomarker in the DNA – a specific portion of the DNA strand that contains instructions for a specific function.
When the rocket returned, the researchers were not expecting to find functioning DNA on the exterior features, but they did. The report notes that a small amount of DNA was found in all three locations with as much as a third of the DNA still functioning.
The study is only a small step towards better understanding the possibility of forward contamination. The researchers note that the DNA used in the experiment was not chromosomal DNA like that of humans, but was plasmid DNA which can be found in some bacteria. The study did not involve the larger chromosomal DNA, but suggests that a separate experiment should be considered.
"We cannot say how these big chromosomal DNA molecules would react under the same conditions and this should be investigated in a separate experiment. In general, we think that survival of microorganisms or of 'molecules of life' during re-entry requires a combination of different favorable and 'protective' factors and may be therefore not the 'rule', but more a probable, but seldom case. But – nevertheless – DNA survival is possible, as demonstrated in our experiment."