Junpei Koike

Survival rates of some terrestrial microorganisms under simulated space conditions

In connection with planetary quarantine, we have been studying the survival rates of nine species of terrestrial microorganisms (viruses, bacteria, yeasts, fungi, etc.) under simulated interstellar conditions. If common terrestrial microorganisms cannot survive in space even for short periods, we can greatly reduce expenditure for sterilizing space probes. The interstellar environment in the solar system has been simulated by low temperature, high vacuum (77 k, 4 x 10(-6) torr), and protons irradiation from a Van de Graaff generator. After exposure to a barrage of protons corresponding to about 250 years of irradiation in solar space, Tobacco mosaic virus, Bacillus subtilis spores, Aspergillus niger spores and Clostridiun mangenoti spores showed survival rates of 82%, 45%, 28%, and 25%, respectively. Furthermore. pathogenic Candida albicans showed 7% survival after irradiation corresponding to about 60 years in space.

Studies in the search for life on Mars.

The ability of living organisms to survive extraterrestrial conditions has implications for the origins of life in the solar system. We have therefore studied the survival of viruses, bacteria, yeast, and fungi under simulated Martian conditions. The environment on Mars was simulated by low temperature, proton irradiation, ultraviolet irradiation, and simulated Martian atmosphere (CO2 95.46%, N2 2.7%, water vapor 0.03%) in a special cryostat. After exposure to these conditions, tobacco mosaic virus and spores of Bacillus, Aspergillus, Clostridium, and some species of coccus showed significant survival.

Fundamental studies concerning planetary quarantine in space

If there is a possibility that the organisms carried from Earth to space can live for a significant period on planets, the contamination of planets should be prevented for the purpose of future life-detection experiments. In connection with quarantine for interplanetary missions, we have examined the survivabilities of terrestrial microorganisms under simulated space conditions. In this study, examined the survivabilities of terrestrial organisms under simulated Mars conditions. The Mars conditions were simulated by ultraviolet (UV) and proton irradiation under low temperature, high vacuum, and simulated gaseous conditions. After exposure to the simulated Mars condition, the survivabilities of the organisms were examined. The spores of Bacillus subtilis and Aspergillus niger, some anaerobic bacterias and algaes, showed considerably high survivabilities even after UV and proton irradiation corresponding to 200 years on Mars. This subject is not restricted to academic curiosity but concerns problems involving the contamination of Mars with terrestrial organisms carried by space-probes.

The ABS (Autonomous Biological System): Spaceflight Results from a Bioregenerative Closed Life Support System

Materially-closed aquatic life support systems containing vascular plants, invertebrate animals, algae and microbes were tested in three space flight experiments with ground controls. Termed Autonomous Biological Systems (ABS), the 0.9 liter systems were completely isolated from spacecraft life support systems and cabin atmosphere contaminants, and needed minimal intervention from astronauts. The first experiment, aboard the Space Shuttle in 1996 for 10 days, was the first time that aquatic angiosperms were successfully grown in space. The second and third experiments aboard the Mir space station had 4-month durations, in 1996-97 and 1997-98, and were the first time that higher organisms (aquatic invertebrate animals) completed their life cycles in space. Compared to the ground control ABS, the flight units showed clearer water and slightly higher total organic carbon and soluble free amino acids. ABS units from all 3 flights returned as diverse and complex ecosystems. The ABS are the first completely bioregenerative, closed ecological life support systems to thrive in space, demonstrating their efficacy for research in space biology and gravitational ecology.

Cultivation of bacterial with ecological capsules in space

Abstract A hermetically materially-closed aquatic microcosm containing bacteria, algae, and invertebrates was developed as a tool for determining the changes of ecological systems in space. The species composition was maintained for more than 365 days. The microcosm could be readily replicated. The results obtained from the simulation models indicated that there is a self-regulation homeostasis in coupling of production and consumption, which make the microcosm remarkably stable, and that the transfer of metabolites by diffusion is one of the important factors determining the behavior of the system. The microcosms were continuously irradiated using a 60 Co source. After 80 days, no elimination of organisms was found at any of the three irradiation levels (0.015, 0.55 and 3.0 mGy/day). The number of radio-resistance bacteria mutants was not increased in the microcosm at three irradiation levels. We proposed to research whether this microcosm is self-sustainable in space.

Search for bioorganic compounds and organisms on Mars

A prototype of new instrument is under construction as a part of Russian Mars program to search for bioorganic compounds and microorganisms which might be frozen in rock under the places where the traces of water were found or near the poles of Mars. The proposed instrument consists of a quadrupole mass spectrometer (QMS) to detect chemical compounds and a fluorescent microscope system (FMS) to detect organisms and bioorganic compounds in bulk.

Exobiology missions proposed in Japan to utilize International Space Station

Abstract The Japanese portion of International Space Station offers opportunities to conduct exobiology experiments and observations at its exposed facility. Preparatory studies have been conducted to define proposals for its possible utilization. Research subjects have been proposed from quite diverse fields of exobiology. It ranges from a basic scientific mission, such as a survey on formation and fate of organic materials under space environment, to a part of an engineering project related to quarantine technology for planetary probes dedicated to exobiology exploration. Besides technical feasibility of implementation of those payloads on the space system, scientific assessment is strongly required to elucidate key issues of exobiology conducted in near Earth orbit. Even research facilities in low Earth orbit, although literally in space, give quite a different environment from that of interstellar space in many aspects. Scientific significance of conducting exobiology there should be based on uniqueness of employing microgravity and its synergetic effects with other factors for exobiology. Because of the quite limited chance of executing space experiments, as well as high cost of its execution, proposed subjects should be proved to possess great competitiveness against studies on the ground where space environment could also be well simulated with less cost. An international forum for exobiology might play an important role to formulate prioritized plan and strategy of the discipline. Such a body could orchestrate exobiology in Earth orbit under complementary relationships among scientific endeavors carried on by scientists who participate in collaborative efforts.