Print button

Abstract EANA2025-5


The Biopause project: balloon experiments to observe the upper boundary of the terrestrial biosphere

 

Sohsuke Ohno (1), Norimune Miyake (1), Osamu Okudaira (1), Ko Ishibashi (1), Yuko Kawaguchi(1)(2), Keisuke Maeda(1)(3), Manabu Yamada (1), Issei Iijima (4), Yusuke Takahashi (5), Satoshi Nonaka (4), Takahiro Segawa (6), and Hideyuki Fuke (4)
(1)Planetary Exploration Research Center, Chiba Institute of Technology, Japan, (2) Saitama University Research Administration Office, Saitama University, Japan, (3) Department of Space Systems Engineering, Kyushu Institute of Technology, Japan, (4) Institute of Space and Astronautical Science, JAXA, Japan, (5) Faculty of Engineering, Hokkaido University, Japan, (6) Graduate Faculty of Interdisciplinary Research Faculty of Medicine Basic Science for Clinical Medicine, University of Yamanashi, Japan


The “biopause” is the upper boundary of the biosphere. Understanding the biopause and the biological flux across it is crucial for comprehending the universality, distribution, origin, and evolution of life in the universe. However, the biopause has not been extensively investigated before and remains poorly understood.
The most direct information available for investigating the biopause is the distribution and dynamics of life in the stratosphere. It is widely accepted that the tropospheric atmosphere contains many species of living microbes. In contrast, the biological mass in the stratosphere is thought to be small because the flux of microbes from the troposphere to the stratosphere is minimal, and the dynamical and biological lifetimes in the stratosphere would be short. However, the possible presence of microbes in the stratosphere has been reported in previous experiments using balloons, aircraft, and rockets. To gain a deeper understanding of the biopause, cleaner experiments that minimize tropospheric contaminations and more diversified sample analysis methods are required.
The Biopause project is a stratospheric bioaerosol sampling project utilizing the scientific balloons of the Japan Aerospace Exploration Agency (JAXA). Our first balloon experiment, conducted in 2016, involved collecting aerosol particles in the stratosphere using a newly developed descending inertial impactor. The third balloon experiment of the Biopause project, in 2019, aimed to observe the vertical distribution of stratospheric microbes and establish a diversified analytical method. For this study, we developed a new descending inertial impactor sampler, which dramatically reduces biological contamination during atmospheric sampling. The recovered sample was analyzed using a fluorescence microscope, cultivation, and a scanning electron microscope (SEM). 
In this paper, we summarize the results of the balloon experiments conducted as part of the Biopause project, report the findings of the latest balloon experiment, and discuss future experimental plans to determine the biopause observationally.