[M-IS17] Astrobiology

[MIS17-13] Third year results and current status of Tanpopo: Capture and exposure experiment of micrometeoroids and microbes on Exposure Facility of International Space Station

*Akihiko Yamagishi^1,2, Hirofumi Hashimoto², Hajime Yano², Yuko Kawaguchi⁹, Shin-ichi Yokobori¹, Kensei Kobayashi³, Mita Hajime⁴, Hikaru Yabuta⁵, Masumi Higashide⁶, Makoto Tabata⁷, Eiichi Imai⁸ (1.Tokyo University of Pharmacy and Life Science, Department of Molecular Biology, 2.ISAS/JAXA, , 3.Yokohama National University, , 4.Fukuoka Institute of Technology, , 5.Hiroshima University, 6.Japan Aerospace Exploration Agency, 7.Chiba University, 8.Nagaoka University of Technology, 9.Chiba Institute of Technology)

Keywords:Microbes, Organics, Internationa Space Station

Tanpopo, a dandelion in Japanese, is a plant species whose seeds with floss are spread by wind.We proposed this mission to examine possible interplanetary migration of microbes, and organic compounds at the Exposure Facility of Japan Experimental Module (JEM: KIBO) of theInternational Space Station (ISS) [1-4]. The Tanpopo mission consists of six subthemes: Capture of microbes in space (Subtheme 1), exposure of microbes in space (Subtheme 2), analysisof organic compounds in interplanetary dust (Subtheme 3), exposure of organic compounds inspace (Subtheme 4), measurement of space debris at the ISS orbit (Subtheme 5), and evaluationof ultralow-density aerogel developed for the Tanpopo mission (Subtheme 6). Exposure Panels for exposure of microbes and organic materials and Capture Panels for aerogel were launched onApril 2015. The Panels were placed on the Exposed Experiment Handrail Attachment Mechanism (ExHAM) in the ISS. The ExHAM with Panels were placed on the Exposure Facilityof KIBO (JEM) with the Japanese robotic arms through the airlock of KIBO. The trays andpanels were exposed for more than one year. The first set of Capture Panels and an ExposurePanel were retrieved on June 2016, returned to the ground and passed over to Tanpopo teamfor the analyses in September. Second- and third- year sets have been returned in 2017 and2018, respectively. Aerogel blocks in Capture Panels are inspected by the automated microimage detector CLOXS. Tracks and particles identified will be used for organic and inorganiccompounds, as well as microscopic analyses [3]. An Exposure Panel consists of 20 ExposureUnits. The returned Exposure Panel was disassembled to the units, each was handed overto the researchers for organic compound and microbiological analyses [4] to test the panspermia hypothesis in the latter [5,6]. Environmental data and survival of a radioresistant speciesDeinococcus aetherius after one-year exposure in space have been published [7]. Current statuswill be presented.

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2)Kawaguchi Y, et al.: Investigation of the interplanetary transfer of microbes in the Tanpopomission at the Exposed Facility of the International Space Station. Astrobiology, 16, 1-14(2016)
3)Kawaguchi Y, et. al.: Fluorescence imaging of microbe- containing particles that had beenshot from a two-stage light-gas gun into an ultra-low density silica aerogel. Origins of Life andEvolution of Biospheres, 44, 43-60 (2014)
4)Kawaguchi Y, et. al.: The possible interplanetary transfer of microbes: Assessing the viability of Deinococcus spp. under the ISS environmental conditions for performing exposureexperiment of microbes in the Tanpopo mission. Origins of Life and Evolution of Biospheres43, 411-428 (2013.)
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7) Yamagishi, A. et al. Environmental Data and Survival Data of Deinococcus aetherius fromthe Exposure Facility of the Japan Experimental Module of the International Space Stationobtained by the Tanpopo Mission. Astrobiology, 18, 1369-1374, (2018)