Yoji Ishikawa

An overview of challenges in modeling heat and mass transfer for living on Mars.

Abstract:  Engineering a life‐support system for living on Mars requires the modeling of heat and mass transfer. This report describes the analysis of heat and mass transfer phenomena in a greenhouse dome, which is being designed as a pressurized life‐support system for agricultural production on Mars. In this Martian greenhouse, solar energy will be converted into chemical energy in plant biomass. Agricultural products will be harvested for food and plant cultivation, and waste materials will be processed in a composting microbial ecosystem. Transpired water from plants will be condensed and recycled. In our thermal design and analysis for the Martian greenhouse, we addressed the question of whether temperature and pressure would be maintained in the appropriate range for humans as well as plants. Energy flow and material circulation should be controlled to provide an artificial ecological system on Mars. In our analysis, we assumed that the greenhouse would be maintained at a subatmospheric pressure under 1/3‐G gravitational force with 1/2 solar light intensity on Earth. Convection of atmospheric gases will be induced inside the greenhouse, primarily by heating from sunlight. Microclimate (thermal and gas species structure) could be generated locally around plant bodies, which would affect gas transport. Potential effects of those environmental factors are discussed on the phenomena including plant growth and plant physiology and focusing on transport processes. Fire safety is a crucial issue and we evaluate its impact on the total gas pressure in the greenhouse dome.

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.

Formation of prebiotic organics in space: Its simulation on ground and conceptual design of space experiment in earth orbit

Abstract The formation of prebiotic organics in outer space has been simulated on ground. In order to verify abiotic formation of such compounds in earth orbit, the concept of cosmobiology experiment was developed. Simulated interstellar ice over dust grains is exposed to vacuum ultraviolet light and other space environment to induce organic formation. A system configuration and its engineering specification were determined to meet the scientific requirements, which were defined by the ground based study. The system consists of cryogenics to keep volatile species solidified, optics to filter and amplify the ultraviolet portion of the solar light for the accelerated irradiation of sample, and analysis subsystem to evaluate formation of organics in-situ together with post flight analysis of involatile products in trace.

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.

Strategy for Detection of Bioorganic Compounds on Mars

It is probable that early Mars had the same type of atmosphere as early Earth, which is a mixture of carbon dioxide, carbon monoxide, nitrogen and water (Kasting, 1990). Irradiation of high energy particles to such a gas mixture caused the formation of amino acid precursors (Kobayashi et al., 1990, 1991, 1995a). On the Earth, life was generated using such endogenously-formed organic compounds, with exogenous organic compounds carried by comets (Kobayashi et al., 1995b) about 4 billion years ago. We can expect that organic compounds could have been formed on the primitive Mars.

Possible formation of organic compounds on Mars

It is probable that early Mars had the same type of atmosphere as early Earth, which is a mixture of CO2, CO, N2 and H20. Irradiation of high energy particles to such a gas mixture caused the formation of amino acid precursors (Kobayashi et al., 1990). It is believed that life was born on the earth using such endogenously-formed organic compounds, with exogenous organic compounds carried by comets (Kobayashi et al., 1995). We can expect that organic compounds could have been formed on the primitive Mars, though the Viking results did not show the presence of organic compounds on Mars. If we choose the other sampling sites and/or the other analytical methods than those of the Viking Project, organic compounds may be detected. Here we discuss possible organic compounds on Mars and analytical methods for them.

Martian Soil Analysis

The surface materials of Mars have been investigated through the spectroscopic observation from Earth and the orbiters, several types of detailed analyses by Viking landers, and the analyses of SNC meteorites of possible Martian origin. Especially, the X-ray fluorescence spectrometer, the GCMS, and three biological experiments of Viking landers provide a tremendous amount of information on the chemical, physical, and mechanical properties of the surface materials. Such Viking results, however, have been the focus of continuous reexamination and reinterpretation even 20 years from the Viking launch.

Simulation of interstellar chemical evolution in a low temperature plasma

In order to simulate the interstellar chemical evolution, the chemical process was studied in a laboratory plasma flow. The apparatus was so designed as to establish the similarity between laboratory and cosmic conditions. The plasma temperature was found to be less than 100 K in the downstream region. HCN, HC3N, H2CO, and several kinds of hydrocarbons were produced from the plasma whose elementary composition was approximately same as the cosmic abundance. Based on the analysis by laser-induced-fluorescence method, HCN and HC3N were concluded to be synthesized via CN loss reactions, while it was unlikely that the syntheses of C2H2 and H2CO were related to the generation or depletion of C2.