Scientists from the Georgia Institute of Technology and NASA announced the discovery of significant numbers of living microorganisms (in majority bacteria) in the middle and upper troposphere, that section of the atmosphere approximately four to six miles above the Earth's surface in the Jan. 28, 2013, issue of the journal Proceedings of the National Academy of Sciences.
The discovery was made during the sampling took place before, during and after two major tropical hurricanes - Earl and Karl - in 2010 by NASA's Genesis and Rapid Intensification Processes (GRIP) program.
Whether the microorganisms routinely inhabit this portion of the atmosphere - perhaps living on carbon compounds also found there - or whether they were simply lofted there from the Earth's surface is not yet known.
The finding is of interest to atmospheric scientists, because the microorganisms could play a role in forming ice that may impact weather and climate. Long-distance transport of the bacteria could also be of interest for disease transmission models. The microorganisms were found to be the appropriate size to facilitate the formation of water droplets and ice in the regions where they were discovered.
When the air masses studied originated over the ocean, the sampling found mostly marine bacteria. Air masses that originated over land had mostly terrestrial bacteria. The researchers also saw strong evidence that the hurricanes had a significant impact on the distribution and dynamics of microorganism populations.
“The study showed that viable bacterial cells represented, on average, around 20 percent of the total particles detected in the size range of 0.25 to 1 microns in diameter. By at least one order of magnitude, bacteria outnumbered fungi in the samples, and the researchers detected 17 different bacteria taxa - including some that are capable of metabolizing the carbon compounds that are ubiquitous in the atmosphere - such as oxalic acid.”
The research was reviewed at the Eureka Alert website the date of publication.