Four-Year Operation of Tanpopo: Astrobiology Exposure and Micrometeoroid Capture Experiments on the JEM Exposed Facility of the International Space Station

Abstract

The Tanpopo experiment was the first Japanese astrobiology mission on board the International Space Station. It included exposure experiments of microbes and organic compounds as well as a capture experiment of hypervelocity impacting microparticles. We deployed three Exposure Panels, each consisting of 20 Exposure Units that contained microbes, organic compounds, an alanine UV dosimeter or an ionizing radiation dosimeter. The three Exposure Panels were situated on the zenith face of the Exposed Experiment Handrail Attachment Mechanism (ExHAM) that was pointing in zenith direction toward space, which was attached on a handrail of the Japanese Experiment Module (Kibo) Exposed Facility ( JEM-EF) outside the International Space Station. The three Exposure Panels were one by one retrieved and returned to the ground after approximately 1, 2, and 3 years of exposure to the space environment. Capture Panels, each of which contained one or two blocks of amorphous silica aerogel, were exposed to collect hypervelocity impact microparticles. Possible captured particles may include micrometeoroids, human-made orbital debris, and natural terrestrial particles. Each year, Capture Panels containing from 11 to 12 aerogel blocks were attached to the three faces of the ExHAM (pointing to zenith, ram, and port); they remained in place for about 1 year and were then returned to the laboratory. This process was repeated three times, in total, during 2015-2018. Additional exposure of a Capture Panel facing ram was conducted between 2018 and 2019. Once the aerogel blocks were returned to the laboratory, they were encapsulated in dedicated transparent plastic cases and optically inspected by a specially designed microscopic system. Once located and recorded, hypervelocity impact signatures were excavated one by one and distributed for further detailed analyses. The apparatus, operation, and environmental factors of all the Tanpopo experiments are summarized in this article.

Memory Effect on the Survival of Deinococcus radiodurans after Exposure in Near Space

“…It can survive acute exposure to up to 5 kGy of gamma radiation and up to 1,000 J/m 2 of UV radiation without loss of viability or mutation ( 47 – 54 ). The viability of D. radiodurans exposed to solar and cosmic radiations has been confirmed by the Exposure Facility of the Japanese Experimental Module (JEM) of the ISS during the space mission Tanpopo ( 18 , 20 , 21 , 25 , 55 ). This provides evidence that this bacterium can be used for experiments in near space.…”

Solid grains ejected from terrestrial exoplanets as a probe of the abundance of life in the Milky Way

“…These grains from terrestrial exoplanets can be collected by detectors placed in space, utilizing a low-density capture media like silica aerogel that enables capture of hypervelocity particles with mild deceleration and hence minimal damage to biosignatures (Westphal et al 2014;Yamagishi et al 2021). A very large total effective area (hopefully comparable to Earth, or ∼10 3 km 2 to expect one particle detection per year) is necessary to detect these particles, but it may be possible in the future, depending on technological developments and humanity's advance into space.…”

Space Radiobiology

“…Examples of short-term experiments of up to 2 weeks in LEO combining radiation dosimetry and biological investigations were loaded on Space Shuttles (e.g., STS 9,42,45,65), on free-flying satellites (e.g., LDEF, EURECA, BIOPAN 1-6) and on the MIR space station (Perseus mission). Later on, similar long-term experiments were performed on the International Space Station (ISS) (EXPOSE-E, -R, -R2) [11,12].…”