Abstract_EANA2024-77

Abstract EANA2024-77

Biological experiments in Tanpopo-5 and Tanpopo-6 (Space exposure experiments for microbes and organic compounds at the Exposure Facility of the Japanese Module of the International Space Station)

Shin-ichi Yokobori (1), Tomomichi Fujita (2), Kaori Tomita-Yokotani (3), Tomoko Abe (4), Hiroshi Katoh (5), Yuji Hiwatashi (6), Atsushi Kume (7), Hirofumi Hashimoto (8), Akihiko Yamagishi (1), & Hajime Mita (9)

(1) Tokyo University of Pharmacy and Life Sciences, Japan, (2) Hokkaido University, Japan, (3) The University of Tsukuba, Japan, (4) Tokyo Denki University, Japan, (5) Mie University, Japan, (6) Miyagi University, Japan, (7) Kyushu University, Japan, (8) Japan Aerospace Exploration Agency, Janan, and (9) Fukuoka Institute of Technology, Japan

Various space exposure experiments of microbes have been performed to evaluate the possibility of "panspermia" (reviewed in Cottin, H., et al. (2017) Space Sci. Rev. 209: 83). Previous studies have shown that microbes shielded by small fragments of rock, by a mixture of sugar and clay, or by the cells themselves with sufficient thickness to protect them from UV radiation have survived in space for a long period of time (e.g. Onofri, S., et al. 2012. Astrobiol. 12: 508; Kawaguchi, Y., et al. (2013) Orig. Life Evol. Biosphere 43:411). The "Tanpopo" experiment was conducted using the Exposure Facility (EF) of the Japanese Experiment Module (JEM, KIBO) of the International Space Station (ISS) [Yamagishi, A., et al. (2018) Astrobiol. 18:1369; Yamagishi, A., et al. (2021) Astrobiol. 21:1451]. For example, the survival of Deinococcus spp. in space was evaluated [Kawaguchi, Y., et al. (2020) Front. Microbiol. 11:2050]. In addition, the survival of the terrestrial cyanobacterium Nostoc sp. HK-01 in space was evaluated [Tomita-Yokotani, K., et al. (2021) Astrobiol. 21:1505]. Following the Tanpopo experiment, Tanpopo-2, -3, and -4 were conducted on the ISS EF; space exposure experiments of Deinococcus radioduans and Nostoc sp. as well as the moss Physcomitrium patens and other microbes were continued (results will be published elsewhere).

For further understanding of panspermia in space, it is important to analyze the difference and similarity of the effects on the survival of microbes between the LEO environment and the deep space environment (far from the influence zone of the Earth's magnetic field). As a first step, in our opinion, the microbes must be directly exposed to the space environment in the space exposure experiment in the LEO environment. If the survival rate of microbes show a large difference between direct exposure and indirect exposure (using a cover window made of such as MgF2), future experiments of exposing microbes and organic compounds in the deep space environment, which will be conducted at the gateway of the lunar space station in the Artemis mission and on the lunar surface, will need to be conducted in a completely direct exposure style.

Based on the above consideration, we conducted the fifth space exposure experiment on the EF of the ISS (Tanpopo-5) and are conducting the sixth (Tanpopo-6). The space exposure experiment of Tanpopo-5 was conducted from March 2023 for 60 days, and that (approximately 9 months) of Tanpopo-6 started in November 2023. Both Tanpopo-5 and Tanpopo-6 consist of several space exposure experiments with different targets and conditions. Among them, some experiments focus on performing "direct" space exposure experiment. For example, in Tanpopo-5, D. radiodurans was exposed directly (without glass cover) and indirectly (with MgF2 window) to compare the effects of the presence of MgF2 window which eliminates short wavelength UV and low egergy particles. In addition, space exposures were performed on the moss plant P. patens, the cyanobacterium Nostoc sp. and the fission yeast Schizosaccharomyces pombe.

The current status of Tanpop-5 and Tanpopo-6 and the prospects for our future space experiments will be discussed.