Determining the location of the “biopause” (i.e., the upper boundary of the biosphere of the Earth) and the biological flux across the biopause are key to our understanding of the universality, distribution, origin, and evolution of life in the universe. It is widely accepted that the tropospheric atmosphere contains bioaerosol, although the flux of microbes from the troposphere to the stratosphere is small and dynamical and biological lifetime in the stratosphere are short. However, the presence of microbes in the stratosphere has been recorded in previous experiments using balloons, aircraft, and rockets. The most direct information available that can be used to investigate the biopause is the distribution and dynamicity of life in the middle atmosphere.
The Biopause project used scientific balloons of the Japan Aerospace Exploration Agency (JAXA) to develop an overview of the stratospheric biosphere and the dynamics of biological flux in the stratosphere. The descending inertial impactor sampler was transported to the stratosphere using a balloon, where the balloon was released from the sampler. Sample collection was conducted as the sampler descended by parachute. This method reduces biological contamination dramatically as the particles that adhere to the balloon and the wall of the sampler cannot enter the sampler during the descent because the descent velocity of the particles (as determined by Stoke’s law) is less than the descent velocity of the sampler.
Our first balloon experiment was conducted on June 8, 2016. The valves of the sampler were opened during its descent from an altitude of 27 to 13 km as planned. The recovered sample was analyzed using a fluorescence microscope and a scanning electron microscope (SEM). Using a fluorescence microscope, we identified 21 microbes on the impactor plate in the sampler. We also analyzed the collected aerosol particles using an SEM. In the presentation, we show the detailed results of the fluorescence microscope and SEM analysis.
