To reach this conclusion, a team of scientists led by Athanasios Nenes rode aboard several NASA DC-8 aircraft to the middle and upper troposphere regions of the atmosphere above the Caribbean Sea and portions of the Atlantic Ocean. There, at about 6 miles (10 km) above the surface, they took samples of rarified air using onboard instruments and an array of filters.
The various trips that encompassed the Genesis and Rapid Intensification Processes campaign were timed so that the researchers could take samples both before and after a pair of tropical hurricanes swept through the regions below, namely hurricanes Earl and Karl in 2010.
Once back at the lab, the scientists used genetic techniques (i.e. polymerase chain reaction (PCR) and gene sequencing) to determine which kinds of microorganisms were present at such extreme altitudes, and in what quantities. According to the researchers, it was the first study of its kind — a paper that has now been published in the Proceedings of the National Academy of Sciences.
What they discovered came as a complete surprise — both in terms of the diversity of microbial life, and also the quantity. The troposphere, it would appear, is home to its own high-altitude microbiome.
Specifically, the researchers found mostly marine bacteria, while air masses that originated over land had mostly terrestrial bacteria. Clearly, the hurricanes were spewing these organisms high up into the atmosphere, creating a dynamic mixture. In terms of numbers, 20% of the particles detected were from bacterial cells ranging from 0.25 to 1 microns in diameter; and in terms of distribution, there were about 144 bacterial cells found in every cubic foot of air.
They also found fungi, but not nearly as much as the bacteria.
Of the bacteria discovered, there were 17 different types, including some capable of metabolizing atmospheric carbon compounds like oxalic acid. This may explain why the hardy bacteria is capable of surviving at such a height.
But not only that, researchers also speculate that these particular microorganisms could be affecting the weather. They theorize that these organisms could be contributing to cloud formation via ice accumulation — a kind of bacterial cloud seeding. "[T]he microbiome," write the researchers, "is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate."
As another interesting note, the researchers also discovered Escherichia and Streptococcus bacteria — microbes that are associated with human and animal feces — and by consequence, diseases. The scientists now wonder — because what goes up must come down — if the tropospheric layer may be contributing to the spread of illnesses around the globe.
Finally, because these bacteria are able to survive such harsh conditions, this research is also of significance to the search for extraterrestrial life and the field of astrobiology. It's conceivable, given these observations, that microbial life may be discovered in the atmospheres of exoplanets.
Read the entire study here.
Source: io9.com.