Scientists at the Georgia Institute of Technology have announced that they've discovered a significant number of living microorganisms, primarily bacteria, in the middle and upper troposphere using genomic techniques.
The troposphere is a section of the atmosphere that is about four to six miles above the Earth's surface.
Researchers are not yet sure whether the microorganisms habitually reside in the troposphere, or whether they were sent into the middle and upper troposphere from the Earth's surface. The scientists believe that the microorganisms could play an important role in forming ice that affects weather and climate.
The microorganisms were found in air samples that were obtained through NASA's Genesis and Rapid Intensification Process (GRIP) program to examine low and high altitude air masses linked to tropical storms. The sampling was conducted from a DC-8 over land and ocean before, during and after hurricanes Earl and Karl in 2010.
Kostas Konstantinidis, an assistant professor in the School of Civil and Environmental Engineering at the Georgia Institute of Technology, said in a statement:
“We did not expect to find so many microorganisms in the troposphere, which is considered a difficult environment for life. There seems to be quite a diversity of species, but not all bacteria make it into the upper troposphere.”
The researchers used genomic techniques such as polymerase chain reaction and gene sequencing to examine the filters from a filter system that gathered the microorganisms from outside air entering the plane's sampling probes. This allowed researchers to identify the microorganisms as well as estimate their numbers without having to rely on more conventional cell-culture techniques.
Researchers found that samples from air masses over the ocean contained mostly marine bacteria, while samples from air masses over land contained mostly earthly bacteria. They also found convincing evidence that the hurricanes had a large effect on the distribution and dynamics of microorganism populations.
Athanasios Nenes, a professor at the Georgia Tech School of Earth and Atmospheric Sciences and School of Chemical and Biomolecular Engineering, commented:
“In the absence of dust or other materials that could provide a good nucleus for ice formation, just having a small number of these microorganisms around could facilitate the formation of ice at these altitudes and attract surrounding moisture. If they are the right size for forming ice, they could affect the clouds around them.”
Researchers would like ton conduct further research to determine whether certain types of bacteria are better than others at surviving in the middle and upper troposphere. They'd also like to learn more about the microorganisms and determine whether or not they are carrying on metabolic functions this high in the Earth's atmosphere.
“For these organisms, perhaps, the conditions may not be that harsh. I wouldn’t be surprised if there is active life and growth in clouds, but this is something we cannot say for sure now.”
The study’s findings were recently published in the journal Proceedings of the National Academy of Sciences.