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Kurosawa K, Genda H, Hyodo R, Yamagishi A, Mikouchi T, Niihara T, Matsuyama S, Fujita K. Assessment of the probability of microbial contamination for sample return from Martian moons II: The fate of microbes on Martian moons. LIFE SCIENCES IN SPACE RESEARCH 2019; 23:85-100. [PMID: 31791609 DOI: 10.1016/j.lssr.2019.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 06/27/2019] [Accepted: 07/10/2019] [Indexed: 05/26/2023]
Abstract
This paper presents a case study of microbe transportation in the Mars-satellites system. We examined the spatial distribution of potential impact-transported microbes on the Martian moons using impact physics by following a companion study (Fujita et al., in this issue). We used sterilization data from the precede studies (Patel et al., 2018; Summers, 2017). We considered that the microbes came mainly from the Zunil crater on Mars, which was formed during 1.0-0.1 Ma. We found that 70-80% of the microbes are likely to be dispersed all over the moon surface and are rapidly sterilized due to solar and galactic cosmic radiation except for those microbes within a thick ejecta deposit produced by natural meteoroids. The other 20-30% might be shielded from radiation by thick regolith layers that formed at collapsed layers in craters produced by Mars rock impacts. The total number of potentially surviving microbes at the thick ejecta deposits is estimated to be 3-4 orders of magnitude lower than at the Mars rock craters. The microbe concentration is irregular in the horizontal direction due to Mars rock bombardment and is largely depth-dependent due to the radiation sterilization. The surviving fraction of transported microbes would be only ∼1 ppm on Phobos and ∼100 ppm on Deimos, suggesting that the transport processes and radiation severely affect microbe survival. The microbe sampling probability from the Martian moons was also investigatesd. We suggest that sample return missions from the Martian moons are classified into Unrestricted Earth-Return missions for 30 g samples and 10 cm depth sampling, even in our conservative scenario. We also conducted a full statistical analysis pertaining to sampling the regolith of Phobos to include the effects of uncertainties in input parameters on the sampling probability. The most likely probability of microbial contamination for return samples is estimated to be two orders of magnitude lower than the 10-6 criterion defined by the planetary protection policy of the Committee on Space Research (COSPAR).
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Affiliation(s)
- Kosuke Kurosawa
- Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Narashino, Tsudanuma, Chiba 275-0016, Japan.
| | - Hidenori Genda
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Ryuki Hyodo
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Akihiko Yamagishi
- Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Takashi Mikouchi
- The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takafumi Niihara
- Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Shingo Matsuyama
- Aeronautical Technology Directorate, Japan Aerospace Exploration Agency, 7-44-1, Jindaijihigasi-machi, Chofu, Tokyo 182-8522, Japan
| | - Kazuhisa Fujita
- Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
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Cataldi G, Brandeker A, Thébault P, Singer K, Ahmed E, de Vries BL, Neubeck A, Olofsson G. Searching for Biosignatures in Exoplanetary Impact Ejecta. ASTROBIOLOGY 2017; 17:721-746. [PMID: 28692303 DOI: 10.1089/ast.2015.1437] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
With the number of confirmed rocky exoplanets increasing steadily, their characterization and the search for exoplanetary biospheres are becoming increasingly urgent issues in astrobiology. To date, most efforts have concentrated on the study of exoplanetary atmospheres. Instead, we aim to investigate the possibility of characterizing an exoplanet (in terms of habitability, geology, presence of life, etc.) by studying material ejected from the surface during an impact event. For a number of impact scenarios, we estimate the escaping mass and assess its subsequent collisional evolution in a circumstellar orbit, assuming a Sun-like host star. We calculate the fractional luminosity of the dust as a function of time after the impact event and study its detectability with current and future instrumentation. We consider the possibility to constrain the dust composition, giving information on the geology or the presence of a biosphere. As examples, we investigate whether calcite, silica, or ejected microorganisms could be detected. For a 20 km diameter impactor, we find that the dust mass escaping the exoplanet is roughly comparable to the zodiacal dust, depending on the exoplanet's size. The collisional evolution is best modeled by considering two independent dust populations, a spalled population consisting of nonmelted ejecta evolving on timescales of millions of years, and dust recondensed from melt or vapor evolving on much shorter timescales. While the presence of dust can potentially be inferred with current telescopes, studying its composition requires advanced instrumentation not yet available. The direct detection of biological matter turns out to be extremely challenging. Despite considerable difficulties (small dust masses, noise such as exozodiacal dust, etc.), studying dusty material ejected from an exoplanetary surface might become an interesting complement to atmospheric studies in the future. Key Words: Biosignatures-Exoplanets-Impacts-Interplanetary dust-Remote sensing. Astrobiology 17, 721-746.
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Affiliation(s)
- Gianni Cataldi
- 1 AlbaNova University Centre, Stockholm University , Department of Astronomy, Stockholm, Sweden
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
| | - Alexis Brandeker
- 1 AlbaNova University Centre, Stockholm University , Department of Astronomy, Stockholm, Sweden
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
| | - Philippe Thébault
- 3 LESIA-Observatoire de Paris, UPMC Univ. Paris 06, Univ. Paris-Diderot , Paris, France
| | - Kelsi Singer
- 4 Southwest Research Institute , Boulder, Colorado, USA
| | - Engy Ahmed
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
- 5 Royal Institute of Technology (KTH) , Science for Life Laboratory, Solna, Sweden
- 6 Stockholm University , Department of Geological Sciences, Stockholm, Sweden
| | - Bernard L de Vries
- 1 AlbaNova University Centre, Stockholm University , Department of Astronomy, Stockholm, Sweden
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
- 7 Scientific Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC) , Noordwijk, The Netherlands
| | - Anna Neubeck
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
- 6 Stockholm University , Department of Geological Sciences, Stockholm, Sweden
| | - Göran Olofsson
- 1 AlbaNova University Centre, Stockholm University , Department of Astronomy, Stockholm, Sweden
- 2 Stockholm University Astrobiology Centre , Stockholm, Sweden
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