Current status of Tanpopo: Capture and Exposure Experiment of Micrometeoroids and Microbes on Exposure Facility of International 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 the International 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), analysis of organic compounds in interplanetary dust (Subtheme 3), exposure of organic compounds in space (Subtheme 4), measurement of space debris at the ISS orbit (Subtheme 5), and evaluation of 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 on April 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 Facility of KIBO (JEM) with the Japanese robotic arms through the airlock of KIBO. The trays and panels were exposed for more than one year. The first set of Capture Panels and an Exposure Panel were retrieved on June 2016, returned to the ground and passed over to Tanpopo team for the analyses in September. Second- and third- year sets have been returned in 2017 and 2018, respectively. Aerogel blocks in Capture Panels are inspected by the automated micro-image detector CLOXS. Tracks and particles identified will be used for organic and inorganic compounds, as well as microscopic analyses [3]. An Exposure Panel consists of 20 Exposure Units. The returned Exposure Panel was disassembled to the units, each was handed over to 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 species Deinococcus aetherius after one-year exposure in space have been published [7]. Current status will be presented. 1)Yamagishi, A. et al.: Tanpopo: Astrobiology exposure and micrometeoroid capture experiments — Proposed experiments at the Exposure Facility of ISS-JEM. ISTS29 Special Issue Publication 2013-k-49, (2014) 2)Kawaguchi Y, et al.: Investigation of the interplanetary transfer of microbes in the Tanpopo mission 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 been shot from a two-stage light-gas gun into an ultra-low density silica aerogel. Origins of Life and Evolution 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 exposure experiment of microbes in the Tanpopo mission. Origins of Life and Evolution of Biospheres 43, 411-428 (2013.) 5)Arrhenius, S. A.: Worlds in the making: The evolution of the Universe, Harper and Brothers, New York, 1908 6)Horneck, G., Klaus, D. M. and Mancinelli, R. L.: Space microbiology. Microbiol. Mol. Biol. Rev., 74, 121-156 (2010) 7) Yamagishi, A. et al. Environmental Data and Survival Data of Deinococcus aetherius from the Exposure Facility of the Japan Experimental Module of the International Space Station obtained by the Tanpopo Mission. Astrobiology, 18, 1369-1374, (2018)