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Results from the Tanpopo capture panels: Using silica aerogel for retrieving cosmic dust from low-Earth orbits


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An ultralow-density double-layer (0.01 and 0.03 g/cm3) silica aerogel tile was designed with a dedicated aluminum casing. A capture panel (CP) comprised an aerogel tile and its casing for use in the astrobiological Tanpopo mission at the International Space Station (ISS). One of the main objectives of the Tanpopo experiment is to retrieve intact cosmic dust at low-Earth orbit for biochemical analysis in terrestrial laboratories. A total of 60 aerogel tiles were mass-produced, and the CPs were assembled using 36 out of 60 aerogel tiles in a biological clean room. The flight-model CPs were dispatched to the ISS in April 2015. After a sampling period of approximately 1 year, 8 tiles from the first group and 3 tiles from the second group (first-year samples) were returned to Earth in August 2016 and March 2017, respectively. All CPs were disassembled in order to extract the aerogel tiles in an enhanced contamination-controlled environment. For the first 8 tiles, the initial phase of the preliminary analysis, which involved finding the hypervelocity impact cavities on the aerogel caused by cosmic dust, was completed successfully. The results confirmed the existence of multiple dust impact cavities on each aerogel.
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Results from the Tanpopo Capture Panels: Using Silica Aerogel for Retrieving
Cosmic Dust from Low-Earth Orbits
By Makoto TABATA,1) Hirofumi HASHIMOTO,2) Daiki HORIKAWA,3) Eiichi IMAI,4) Junya IMANI,5) Yukihiro ISHIBASHI,6)
Yuko KAWAGUCHI,7) Yoko KEBUKAWA,8) Kensei KOBAYASHI,8) Hajime MITA,9) Kyoko OKUDAIRA,10) Satoshi SASAKI,11)
Shin-ichi YOKOBORI,7) Hajime YANO,2) and Akihiko YAMAGISHI7)
1)Department of Physics, Chiba University, Chiba, Japan
2)Institute of Space and Astronautical Science (ISAS), JAXA, Sagamihara, Japan
3)Institute for Advanced Biosciences, Keio University, Tsuruoka, Japan
4)Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Japan
5)Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
6)Department of Earth and Planetary Sciences, Kyushu University, Fukuoka, Japan
7)Department of Applied Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
8)Department of Chemistry, Chemical Engineering and Life Science, Yokohama National University, Yokohama, Japan
9)Department of Life, Environment and Materials Science, Fukuoka Institute of Technology, Fukuoka, Japan
10)Oce for Planning and Management, University of Aizu, Aizu-Wakamatsu, Japan
11)School of Health Sciences, Tokyo University of Technology, Tokyo, Japan
(Received April 21st, 2017)
An ultralow-density double-layer (0.01 and 0.03 g/cm3) silica aerogel tile was designed with a dedicated aluminum casing. A
capture panel (CP) comprised an aerogel tile and its casing for use in the astrobiological Tanpopo mission at the International Space
Station (ISS). One of the main objectives of the Tanpopo experiment is to retrieve intact cosmic dust at low-Earth orbit for biochemical
analysis in terrestrial laboratories. A total of 60 aerogel tiles were mass-produced, and the CPs were assembled using 36 out of 60
aerogel tiles in a biological clean room. The flight-model CPs were dispatched to the ISS in April 2015. After a sampling period of
approximately 1 year, 8 tiles from the first group and 3 tiles from the second group (first-year samples) were returned to Earth in August
2016 and March 2017, respectively. All CPs were disassembled in order to extract the aerogel tiles in an enhanced contamination-
controlled environment. For the first 8 tiles, the initial phase of the preliminary analysis, which involved finding the hypervelocity
impact cavities on the aerogel caused by cosmic dust, was completed successfully. The results confirmed the existence of multiple
dust impact cavities on each aerogel.
Key Words: Silica Aerogel, Cosmic Dust, Astrobiology, International Space Station, Tanpopo
1. Introduction
Tanpopo is a multifaceted astrobiological experiment re-
searching the origins of life and its migration through space. It
is currently housed by the Japanese Experiment Module (JEM)
of the International Space Station (ISS) at low-Earth orbit
(LEO).1–3) The Tanpopo instruments comprise a cosmic dust-
capture medium and space-exposed panels containing microbes
and organic compounds (see Refs. 4–6) for more details on
the exposure-panel experiments). The dust-capture experiment
primarily aims at detecting terrestrial microbes in dust particles
ejected from the Earth’s surface to LEO by mechanisms that are
not yet well established7) and analyzing interplanetary dust par-
ticles (IDPs) containing prebiotic organic compounds that may
arrive on Earth.8) This composite experiment is currently being
performed using JAXA’s Exposed Experiment Handrail Attach-
ment Mechanism (ExHAM) at the Exposed Facility of the JEM.
The 11 capture media for the 2016 experiment were exposed to
space for a duration of approximately 1 year. The samples were
then returned to Earth for analysis in terrestrial laboratories us-
ing state-of-the-art biochemical methods. The experiment will
be repeated three times (in the original plan). Additionally, 12
capture media for the 2017 experiment are currently exposed to
space. The analyses of the first-year samples have initiated.
2. Use of Silica Aerogel as Dust-capture Media
Cosmic dust (including terrestrial dust, IDPs, and space de-
bris) is captured by certain media at a hypervelocity of up
to 16 km/s in LEO. We developed an ultralow-density (0.01
g/cm3) silica aerogel as the capture medium for hypervelocity
microparticles, which resulted in an almost intact collection of
cosmic dust.9) Silica aerogel, which is a three-dimensional net-
work of nanoscale silica particles (SiO2), is one of the most suit-
able media for cosmic dust sampling owing to its property of be-
ing lightweight and its optical transparency.10, 11) We developed
a dual-density (0.01 and 0.03 g/cm3) layer structure, as shown
in Fig. 1.12) The 0.03-g/cm3base layer provided mechanical
protection to the 0.01-g/cm3surface layer under rocket launch
vibration conditions. We designed a special casing, i.e., a cap-
ture panel (CP), for attaching the aerogel to ExHAM. CP di-
mensions were limited to 100 ×100 ×20 mm3per segment.12)
Between March 2013 and April 2013, the mass production
of 60 double-layer aerogel tiles completed successfully using
Fig. 1. Dual-layer aerogel tile with dimensions of approximately 95 ×
95 ×18 mm3(sample fabricated with a technique same as the one used for
producing flight aerogel tiles). The 0.03-g/cm3layer, except the top surface,
surrounds the 0.01-g/cm3layer.
sterilized tools in a biological clean booth (class 1000) at the
Particle Physics Laboratory in Chiba University.13) We previ-
ously confirmed that a prototype of aerogel tile fabricated in
a contamination-controlled environment was not contaminated
by any environmental microbes.14) The development history
of the aerogel for the Tanpopo mission was recorded.15) Our
method for producing the aerogel was based on our previous
research.16) Single-layer aerogel blocks with a density of 0.03
g/cm3that were used in JAXA’s previous dust-capture mis-
sion17) were manufactured by a company using a method simi-
lar to ours. Employing the 0.01-g/cm3ultralow-density aerogel
in the Tanpopo experiment was challenging as it was expected
to exhibit the best dust-capture performance in the world.
3. An Assembly of CPs
In December 2014, we assembled the CPs, as shown in Fig.
2. A total of 36 double-layer aerogel tiles were installed inside
dedicated aluminum casings in a clean room (class 1000) for
the Tanpopo mission at the Institute of Space and Astronautical
Science (ISAS), JAXA. The casing comprised a body, lid, and
cover. The casings and all of the tools were sterilized by fol-
lowing a specific procedure. In addition, just before covering
the CPs, the top surface of the aerogel tiles was UV-irradiated to
ensure sterile conditions. To facilitate the removal of the aero-
gel from the casing after the in-orbit operation, the aerogel was
placed in a box with an open top, which was made of aluminum
foil (treated with heat at 500C). Subsequently, the foil box was
installed to the CP. The area between the aluminum box and
the casing was filled with superimposed aluminum foil. The
assembly was successful with no damage to the aerogel tiles.
4. The In-orbit Operation
The Tanpopo experimental instruments, including CPs for
a period of 3 years and additional in-orbit operations, were
launched by Space Exploration Technologies Corporation’s
(SpaceX, U.S.A.) unmanned Dragon cargo spacecraft (6th
Commercial Resupply Services, CRS-6) in April 2015. The
Tanpopo payload was stored in the pressurized section of the
Dragon spacecraft and was transferred to the pressurized JEM
Fig. 2. An image of the assembled capture panel. The cover plate is not
by the ISS crew after docking to the ISS. The CPs containing
8 aerogel tiles (2016A samples) were attached to ExHAM-1
(there are two identical ExHAM modules on the JEM) inside
the pressurized module. In May 2015, ExHAM-1 was exposed
to space at the Exposed Facility using a robotic arm through
an airlock, initiating the first year of the Tanpopo experiment.
Similarly, in November 2015, the CPs containing 3 aerogel tiles
(2016B samples) were exposed to ExHAM-2.
Following approximately 1 year of exposure, the 2016A CPs
were recovered inside the pressurized module in June 2016. No
significant damage to the aerogel was observed through visual
inspection during sample packing. Depressurization and repres-
surization in the airlock were gradually performed in order to
minimize changes in the volume of the aerogel tiles. The 2016A
samples returned to Earth on the Dragon CRS-9 return cap-
sule in August 2016 and to the Tanpopo clean room at ISAS in
September 2016. Similarly, the 2016B samples were recovered
inside the pressurized module and returned to Earth on Dragon
CRS-10 in March 2017. They were finally delivered to ISAS in
April 2017. Thus, all first-year 2016 samples were successfully
retrieved. The 2017 samples (12 aerogel tiles) were exposed to
space on ExHAM-1 in June 2016 and are still in operation.
5. Results from CPs
No significant damage to the CPs was found during a brief
check immediately after the delivery to the Tanpopo clean room
at ISAS. In a preliminary analysis of the retrieved aerogel tiles,
a Captured particles Locating, Observation, and eXtraction Sys-
tem (CLOXS) was developed to observe the aerogel tiles for the
purpose of detecting cosmic dust-impact signatures and cutting
small aerogel segments (keystones) containing an impact cav-
ity and captured dust grains. To interface an aerogel tile to the
CLOXS, or more specifically, to define a coordinate system on
the aerogel by fixing it onto the CLOXS for data acquisition, an
aerogel holder made of acrylic resin was developed. This trans-
parent holder enables the observation of the aerogel by using
an optical microscope build into the CLOXS and by keeping it
away from biochemical contamination from dust particles that
might possibly exist in the clean room. The holder comprises a
body and lid and can be almost completely sealed. The holder
was uncovered only during the keystone cutting and extraction
Fig. 3. Aerogel holder containing a retrieved flight aerogel tile.
By October 2016, all 2016A CPs were disassembled and
the aerogel tiles were transferred to their holders tile by tile,
as shown in Fig. 3. This process was conducted inside a
contamination-controlled environment (ISO level 1) created by
a tabletop open clean system (KOACH T500-F, Koken Ltd.,
Japan) in the Tanpopo clean room. Similarly, the 2016B aerogel
tiles were transferred to their holders in April 2017. During the
aerogel transfer process, we regret to report an accidental dam-
age (tile cracking) for the first sample; however, the eect of
this damage on the comprehensive analysis of the captured cos-
mic dust will be insignificant. We believe that the aerogel tiles
became more brittle as they were exposed to space exposure for
a period of approximately 1 year. A modified aerogel-holding
method was used, which functioned well for the later aerogel
samples. In some aerogel tiles, a slight brown discoloration
was observed on the surface exposed to space.
In the initial phase of the preliminary aerogel sample anal-
ysis (2016A) using the CLOXS, optical microscope images of
the surface of each aerogel tile were captured. Surface features
larger than 100 µm (roughly, 10-µm-diameter captured dust was
expected for true impact cavities) were searched and marked
as candidates of hypervelocity impact cavities. These candi-
dates were then entirely assessed for the existence of impact
cavities. Cavity depth information was obtained by focusing
the microscope inside the transparent aerogel step by step. Fi-
nally, multiple impact cavities per aerogel were confirmed. To
perform a comprehensive biochemical analysis of the captured
particles, several keystones containing cavities were extracted
from the aerogel tiles by the CLOXS operating in the KOACH.
Dust grains with an analyzable size were identified in some key-
stones. More thorough results of the dust-impact cavity search
and preliminary analysis will be presented in a separate study.18)
6. Conclusions
We developed flight-model CPs for capturing intact cosmic
dust as part of the Tanpopo mission experiment currently being
performed at the ISS. Samples collected during the first year
have already returned to Earth for analysis. The existence of
dust considered to have been collected at LEO has been con-
firmed. Therefore, the newly developed ultralow-density aero-
gel was successful in collecting cosmic dust. Thorough analysis
of captured particles and further evaluation of aerogel perfor-
mance are still in progress.
We are grateful to the members of the Tanpopo team for their
contributions to this research. Additionally, we are grateful to
Prof. H. Kawai of Chiba University for his assistance in aerogel
production. We would like to thank Yuki Precision Co., Ltd. for
their contributions in manufacturing CPs. Furthermore, we are
thankful to the JEM Mission Operations and Integration Center,
Human Spaceflight Technology Directorate, JAXA. This study
was partially supported by the Hypervelocity Impact Facility
(former name: Space Plasma Laboratory) at ISAS, JAXA, the
Venture Business Laboratory at Chiba University, a Grant-in-
Aid for Scientific Research (B) (No. 16H04823) from the Japan
Society for the Promotion of Science (JSPS), and the Astrobi-
ology Center Program of Japan’s National Institutes of Natural
Sciences (NINS; Grant No. AB282002).
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Full-text available
Unlabelled: The Tanpopo mission will address fundamental questions on the origin of terrestrial life. The main goal is to test the panspermia hypothesis. Panspermia is a long-standing hypothesis suggesting the interplanetary transport of microbes. Another goal is to test the possible origin of organic compounds carried from space by micrometeorites before the terrestrial origin of life. To investigate the panspermia hypothesis and the possible space origin of organic compounds, we performed space experiments at the Exposed Facility (EF) of the Japanese Experiment Module (JEM) of the International Space Station (ISS). The mission was named Tanpopo, which in Japanese means dandelion. We capture any orbiting microparticles, such as micrometeorites, space debris, and terrestrial particles carrying microbes as bioaerosols, by using blocks of silica aerogel. We also test the survival of microbial species and organic compounds in the space environment for up to 3 years. The goal of this review is to introduce an overview of the Tanpopo mission with particular emphasis on the investigation of the interplanetary transfer of microbes. The Exposed Experiment Handrail Attachment Mechanism with aluminum Capture Panels (CPs) and Exposure Panels (EPs) was exposed on the EF-JEM on May 26, 2015. The first CPs and EPs will be returned to the ground in mid-2016. Possible escape of terrestrial microbes from Earth to space will be evaluated by investigating the upper limit of terrestrial microbes by the capture experiment. Possible mechanisms for transfer of microbes over the stratosphere and an investigation of the effect of the microbial cell-aggregate size on survivability in space will also be discussed. Key words: Panspermia-Astrobiology-Low-Earth orbit. Astrobiology 16, 363-376.
Full-text available
The fabrication of an ultralow-density hydrophobic silica aerogel for the intact capture cosmic dust during the Tanpopo mission is described. The Tanpopo experiment performed on the International Space Station orbiting the Earth includes the collection of terrestrial and interplanetary dust samples on a silica aerogel capture medium exposed to space for later ground-based biological and chemical analyses. The key to the mission’s success is the development of high-performance capture media, and the major challenge is to satisfy the mechanical requirements as a spacecraft payload while maximizing the performance for intact capture. To this end, an ultralow-density (0.01 g cm−3) soft aerogel was employed in combination with a relatively robust 0.03 g cm−3 aerogel. A procedure was also established for the mass production of double-layer aerogel tiles formed with a 0.01 g cm−3 surface layer and a 0.03 g cm−3 open-topped, box-shaped base layer, and 60 aerogel tiles were manufactured. The fabricated aerogel tiles have been demonstrated to be suitable as flight hardware with respect to both scientific and safety requirements. Graphical Abstract
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Tanpopo, dandelion, is the name of a grass whose seeds with floss are spread by the wind. We propose the analyses of interplanetary migration of microbes, organic compounds and meteoroids on Japan Experimental Module (JEM) of the International Space Station (ISS). In this paper we will introduce the target and basic design of the project. In "Tanpopo" project, ultra low-density aerogel will be used to capture micrometeoroid and debris. Particles captured by aerogel will be used for several analyses after the initial inspection of the gel and tracks. Careful analysis of the tracks in the aerogel will provide the size and velocity dependence of debris flux. The particles will be analyzed for mineralogical, organic and microbiological characteristics. Aerogels are ready for production in Japan. Aerogels and trays are space proven. All the analytical techniques are ready.
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We are developing a silica-aerogel-based cosmic dust collector for use in the Tanpopo experiment to be conducted on the International Space Station. The mass production of simple two-layer hydrophobic aerogels was undertaken in a contamination-controlled environment, yielding more than 100 undamaged products. The collector, comprising an aerogel tile and holder panel, was designed to resist launch vibration and to conform to an exposure attachment. To this end, a box-framing aerogel with inner and outer densities of 0.01 and 0.03 g/cm$^3$, respectively, was fabricated. The aerogel mounted in the panel passed random vibration tests at the levels of the acceptance and qualification tests for launch. It also withstood the pressure changes expected in the airlock on the International Space Station.
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A wide variety of organic compounds have been found in space, and their relevance to the origin of life is discussed. Interplanetary dust particles (IDPs) are most promising carriers of extraterrestrial organic compounds, but presence of bioorganic compounds are controversial since they are so small and were collected in the terrestrial biosphere. In addition, IDPs are directly exposed to cosmic and solar radiation. Thus, it is important to evaluate the stability of organics in IDPs in space environment. We are planning a novel astrobiology mission named Tanpopo by utilizing the Exposed Facility of Japan Experimental Module (JEM/EF) of the International Space Station (ISS). Two types of experiments will be done: Capture experiments and exposure experiments. In the exposure experiments, organics and microbes will be exposed to the space environments to examine possible alteration of organic compounds and survivability of microbes. Selected targets for the exposure experiments of organic compounds are as follows: Amino acids (glycine and isovaline), their possible precursors (hydantoin and 5-ethyl-5-methyl hydantoin) and complex precursors "CAW" synthesized from a mixture of carbon monoxide, ammonia and water by proton irradiation. In addition to them, powder of the Murchison meteorite will be exposed to examine possible alteration of meteoritic organics in space. We will show the results of preparatory experiments on ground by using a UV lamp, synchrotron facilities, and a heavy ion irradiation facility.
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To investigate the possible interplanetary transfer of life, numerous exposure experiments have been carried out on various microbes in space since the 1960s. In the Tanpopo mission, we have proposed to carry out experiments on capture and space exposure of microbes at the Exposure Facility of the Japanese Experimental Module of the International Space Station (ISS). Microbial candidates for the exposure experiments in space include Deinococcus spp.: Deinococcus radiodurans, D. aerius and D. aetherius. In this paper, we have examined the survivability of Deinococcus spp. under the environmental conditions in ISS in orbit (i.e., long exposure to heavy-ion beams, temperature cycles, vacuum and UV irradiation). A One-year dose of heavy-ion beam irradiation did not affect the viability of Deinococcus spp. within the detection limit. Vacuum (10(-1) Pa) also had little effect on the cell viability. Experiments to test the effects of changes in temperature from 80 °C to -80 °C in 90 min (±80 °C/90 min cycle) or from 60 °C to -60 °C in 90 min (±60 °C/90 min cycle) on cell viability revealed that the survival rate decreased severely by the ±80 °C/90 min temperature cycle. Exposure of various thicknesses of deinococcal cell aggregates to UV radiation (172 nm and 254 nm, respectively) revealed that a few hundred micrometer thick aggregate of deinococcal cells would be able to withstand the solar UV radiation on ISS for 1 year. We concluded that aggregated deinococcal cells will survive the yearlong exposure experiments. We propose that microbial cells can aggregate as an ark for the interplanetary transfer of microbes, and we named it 'massapanspermia'.
Conference Paper
Since late 2000’s, Japanese astrobiologists have started to be involved more into space experiments and missions associated with sample returns and subsequent micro-analyses. Their efforts have resulted in the successful start of the in-orbit operation of the “TANPOPO” mission, named after dandelion, a grass whose seeds with floss are spread by the wind. Originally it was selected as one of the second-round candidates of the JEM-EF science experiments in 2007 and aims six sub-themes such as 1) capture of terrestrial microbes in space, 2) exposure of terrestrial microbes in space, 3) exposure of astronomical organic analogues in space, 4) capture of organic-bearing micrometeoroids in space, 5) space-flight validation of originally developed ultra-low dense aerogels, and 6) orbital debris impact flux assessment at the ISS orbit. 67 tracks larger than 0.1 mm were detected, 11 among them have been handed over to the scientists who are going to analyze microbial, organic and mineralogical characteristics.