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MDA is designed as a test bed for an astrobiology field instrument to detect microbial metabolic activity in terrestrial or extraterrestrial geological soil samples. MDA employs electrochemical sensors in a unique differential chamber configuration, able to detect minute changes in the chemical composition between the two otherwise identical chambers. Both chambers are filled with identical autoclave-sterilized, sample-water mixtures. Only one of the chambers receives an additional minute, non-sterilized inoculation sample. Under the minimal assumptions that the geological sample contained nutrients (energy), organisms, and required water to initiate growth, the differential electrochemical measurements would now allow detection of metabolic activity, in addition to the electrochemical characterization of the soil samples in both chambers.

Thin films continue to play an ever-increasing role in high performance structures for space exploration. Membrane structures have been developed or envisioned for such applications as scientific balloons, deep space antennas, Earth radiometers, radars, concentrators, telescopes, sun shields, solar sails, solar arrays, spacecraft booms, and planetary surface habitats. Inflatable membrane structures can have very high packaging efficiencies, are easy to construct at remote locations and are lightweight because pressure differences provide structural stabilization without the need for rigid supports or internal framework. Recent proposals have suggested construction of an inflatable greenhouse from transparent polymer films for Mars surface operations. This paper reports on the progress to examine the effects of mechanical loading on the rates of photodegradation in transparent polymer films exposed to simulated Mars ultraviolet radiation.

This paper reports on the approach and progress to refine the estimates of the Mars surface photosynthetically active radiation (PAR) on a global scale that is averaged over a longer time period. While the PAR on Mars has been evaluated previously, the results have been limited in scope either temporally or spatially, such as only at a particular landing site or only over the time span of a few months. Understanding the availability of PAR is important in evaluating the practicality of using greenhouses and/or solar irradiance collectors for growing crops during manned missions to the Martian surface. Until surface investigations can be performed, computational modeling of the surface PAR can help to refine site selection and evaluation of engineering approaches and indicate the most favorable location at which to operate a greenhouse. The proposed approach is to combine multispectral irradiance models with global atmospheric opacity models developed from multiyear observations.

Environmentally sealed or isolated life sciences experiments such as plant growth chambers or animal habitats often require active temperature and humidity control. The interaction between the temperature and humidity control system, and performance limitations are shown based on experimental data using a small spaceflight plant growth chamber. Limited availability of electric power, and the chosen control system implementation constrain the obtainable temperature and humidity setpoint combinations.

Small spaceflight life science experiments, such as plant growth chambers and animal habitats, operate in unique environments. The experiments are often sealed systems that control atmospheric constituents, temperature, and humidity. Chemical scrubbers can be an efficient and reliable way to actively remove carbon dioxide for shorter experiment durations because they do not require power or complex technologies to operate. Several commercially available scrubbers were tested in both low and high humidity environments, and at low concentration levels of carbon dioxide similar to those found in plant chamber applications, to find a scrubber that was both effective and efficient for use in small life sciences experiments.

It is proposed to employ a greenhouse for life support on the Martian surface to reduce the equivalent system mass (ESM) penalties encountered with electrical crop lighting. The ESM of a naturally lit plant growth system compares favorably to an electrically lit system when corrections for area are made based on available light levels. A transparent structure should be more efficient at collecting insolation than collectors due to the diffusivity of the Mars atmosphere and inherent transmission losses encountered with fiber optics. The need to provide a pressurized environment for the plants indicates the use of an inflatable structure. Materials and design concepts are reviewed for their applicability to an inflatable greenhouse.

Long distance/duration human space missions demand economical, regenerative life support systems. With naturally available light and low atmospheric pressures, missions to the surface of Mars might employ higher plants in a bioregenerative life support systems housed within a transparent inflatable greenhouse. The primary advantages of an inflatable structure are low mass, derived from pressure stabilization of the structure, the ability to collapse into a small storage volume for transit and ease of construction. Many high performance engineering polymer films exist today that are either highly or mostly transparent. Selection of one of these materials for an inflatable greenhouse to operate in the Mars surface environment poses a number of challenges. First, materials must be strong enough to resist the differential pressure loading between the inside plant environment and the near vacuum of thin Martian atmosphere.

The MarsPort competition, sponsored by the Florida and Texas Space Grant Consortiums, was established to elicit student involvement in the manned exploration of Mars. The RedThumb team, comprised of students from the Aerospace Engineering Sciences Department at the University of Colorado, designed a greenhouse to be deployed on the Martian surface and meet the requirements put out by the 2002 MarsPort competition. This paper addresses the difficulties of engineering systems to operate in the Martian environment including radiation, micrometeorites, and dust storms. Diet requirements and the selection of crops are also discussed. The final greenhouse system includes seven, unmanned inflatable greenhouse modules called AGPods. There is also a manned facility called PlantHAB where AGPods are maintained and harvested and includes and additional 30 m2 for salad type crops.

The Autonomous Garden Pod (AG-Pod) is a modular crop production system that can lower the equivalent system mass (ESM) for bioregenerative life support systems. AG-Pod combines existing technologies, many of which are at the technology readiness level (“TRL”) 8 or 9, into a flight-ready system adaptable to many needs from Space Station microgravity plant research to interplanetary transit and planetary surface food production systems. The plant-rated module resides external to the spacecraft pressurized volume and can use natural direct solar illumination. This reduces the ESM of crop production systems by eliminating the use of spacecraft internal pressurized volume and by reducing power and heat rejection resources that would be needed for full artificial lighting. However, lowering of the crop production ESM is also achieved from the use of lightweight structures including composite and inflatable technology.

Accurate root zone moisture control in microgravity plant growth systems is problematic. With gravity, excess water drains along a vertical gradient, and water recovery is easily accomplished. In microgravity, the distribution of water is less predictable and can easily lead to flooding, as well as anoxia. Microgravity water delivery systems range from solidified agar, water-saturated foams, soils and hydroponics soil surrogates including matrix-free porous tube delivery systems. Surface tension and wetting along the root substrate provides the means for adequate and uniform water distribution. Reliable active soil moisture sensors for an automated microgravity water delivery system currently do not exist. Surrogate parameters such as water delivery pressure have been less successful.

Aeroponics is the process of growing plants in an air/mist environment without the use of soil or an aggregate media. Aeroponics has contributed to advances in several areas of study including root morphology, nutrient uptake, drought and flood stress, and responses to variations in oxygen and/or carbon dioxide root zone concentrations. The adaptability of the aeroponic process that has benefited researchers makes its application to spaceflight plant growth systems appealing. Greater control of growth parameters permits a greater range of crop performance throttling and the elimination of aggregates or common growth substrates lowers system mass, lessens disease propagation between plants, and can decrease the required crew time for both planting and harvesting.

Spaceflight plant growth chambers require an atmosphere control system to maintain adequate levels of carbon dioxide and oxygen, as well as to limit trace gas components, for optimum or reproducible scientific performance. Recent atmosphere control anomalies of a spaceflight plant chamber, resulting in unstable CO2 control, have been analyzed. An activated carbon filter, designed to absorb trace gas contaminants, has proven detrimental to the atmosphere control system due to its large buffer capacity for CO2. The latest plant chamber redesign addresses the control anomalies and introduces a new approach to atmosphere control (low leakage rate chamber, regenerative control of CO2, O2, and ethylene).