Scientific Targets of Tanpopo: Astrobiology Exposure and Micrometeoroid Capture Experiments at the Japanese Experiment Module Exposed Facility of the International Space Station.

Masumi Higashide,Kensei Kobayashi,Hikaru Yabuta,Shin-ichi Yokobori,Akihiko Yamagishi,Hajime Mita,Hajime Yano,Makoto Tabata

doi:10.1089/ast.2020.2426

Abstract

The Tanpopo experiment was the first Japanese astrobiology mission on board the Japanese Experiment Module Exposed Facility on the International Space Station (ISS). The experiments were designed to address two important astrobiological topics, panspermia and the chemical evolution process toward the generation of life. These experiments also tested low-density aerogel and monitored the microdebris environment around low Earth orbit. The following six subthemes were identified to address these goals: (1) Capture of microbes in space: Estimation of the upper limit of microbe density in low Earth orbit; (2) Exposure of microbes in space: Estimation of the survival time course of microbes in the space environment; (3) Capture of cosmic dust on the ISS and analysis of organics: Detection of the possible presence of organic compounds in cosmic dust; (4) Alteration of organic compounds in space environments: Evaluation of decomposition time courses of organic compounds in space; (5) Space verification of the Tanpopo hyper-low-density aerogel: Durability and particle-capturing capability of aerogel; (6) Monitoring of the number of space debris: Time-dependent change in space debris environment. Subthemes 1 and 2 address the panspermia hypothesis, whereas 3 and 4 address the chemical evolution. The last two subthemes contribute to space technology development. Some of the results have been published previously or are included in this issue. This article summarizes the current status of the Tanpopo experiments.

Highlights

The Tanpopo experiment is the first Japanese astrobiology mission on board the Japanese Experiment Module ( JEM, known as Kibo) Exposed Facility (EF) of the International Space Station (ISS)
We evaluated DNA damage under different space exposure conditions using various methods (Table 2): (1) Degree of double strand break of genomic DNA of deinococcal species was visualized by using pulsed field gel electrophoresis (PFGE) (Kawaguchi et al, 2020); (2) Copy numbers of intact rpoB gene in exposed cells were evaluated by quantitative polymerase chain reaction (Kawaguchi et al, 2020); and (3) The mutations of D. radiodurans R1 were evaluated by mutation analysis of the rpoB gene of rifampicin resistance (Fujiwara et al, 2021)
The decomposition of these organic compounds was analyzed, and the results showed that the recovery of target molecules basically depended on their UV/VUV absorption spectra, but that the recovery of the complex amino acid precursors was higher than expected from their spectra

Summary

Introduction

The Tanpopo experiment is the first Japanese astrobiology mission on board the Japanese Experiment Module ( JEM, known as Kibo) Exposed Facility (EF) of the International Space Station (ISS). The exposure units with organics were arranged on exposure panels, which were exposed in the space environment for 1, 2, and 3 years The decomposition of these organic compounds was analyzed, and the results showed that the recovery of target molecules basically depended on their UV/VUV absorption spectra, but that the recovery of the complex amino acid precursors was higher than expected from their spectra. Some of these results are presented in an article in this issue (Kobayashi, et al, 2021). The results suggest that the current debris environment models need to be refined for the short-term variation (Minakami et al, 2020)

Conclusion

Findings

Funding Statement