Technical review of the Laboratory Biosphere closed ecological system facility

Investigation on the influence of isolated environment on human psychological and physiological health

Crewmembers are working and living in isolated environment lacking natural light and perception. Although their health problems have been documented, the mechanism has not been thoroughly investigated. The aim of the present study is to investigate the psychological and physiological influences of isolated environment on crewmember's health. On account of complexity of the isolated environment, it is necessary to have a manually controllable system to simulate research platform-Bioregenerative Life Support System (BLSS). Symptom checklist 90 (SCL-90) was used to complete emotional status test. Urine samples were collected for metabonomics and hormone secretion analysis. Fecal samples were collected for intestinal microorganisms analysis. Crewmembers (n = 4) followed strict daily schedule during the experimental period. Five emotional factors were significantly (P < 0.05) increased, differential metabolites were enriched in tryptophan metabolism pathway, the relative abundance of Prevotella decreased significantly (P < 0.0001) when crewmembers in isolated environment without natural light. Hormone (melatonin, cortisol) secretion rhythm also changed. Significant positive correlation (r = 0.805, P < 0.05) between cortisol secretion and anxiety was observed. In conclusion, natural light simulation in an isolated environment may have a positive effect on the physiological and psychological health of the crewmember.

How to Establish a Bioregenerative Life Support System for Long-Term Crewed Missions to the Moon or Mars

To conduct crewed simulation experiments of bioregenerative life support systems on the ground is a critical step for human life support in deep-space exploration. An artificial closed ecosystem named Lunar Palace 1 was built through integrating efficient higher plant cultivation, animal protein production, urine nitrogen recycling, and bioconversion of solid waste. Subsequently, a 105-day, multicrew, closed integrative bioregenerative life support systems experiment in Lunar Palace 1 was carried out from February through May 2014. The results show that environmental conditions as well as the gas balance between O₂ and CO₂ in the system were well maintained during the 105-day experiment. A total of 21 plant species in this system kept a harmonious coexistent relationship, and 20.5% nitrogen recovery from urine, 41% solid waste degradation, and a small amount of insect in situ production were achieved. During the 105-day experiment, oxygen and water were recycled, and 55% of the food was regenerated. Key Words: Bioregenerative life support systems (BLSS)-Space agriculture-Space life support-Waste recycle-Water recycle. Astrobiology 16, 925-936.

Effects of a spaceflight environment on heritable changes in wheat gene expression

Once it was established that the spaceflight environment was not a drastic impediment to plant growth, a remaining space biology question was whether long-term spaceflight exposure could cause changes in subsequent generations, even if they were returned to a normal Earth environment. In this study, we used a genomic approach to address this question. We tested whether changes in gene expression patterns occur in wheat plants that are several generations removed from growth in space, compared to wheat plants with no spaceflight exposure in their lineage. Wheat flown on Mir for 167 days in 1991 formed viable seeds back on Earth. These seeds were grown on the ground for three additional generations. Gene expression of fourth-generation Mir flight leaves was compared to that of the control leaves by using custom-made wheat microarrays. The data were evaluated using analysis of variance, and transcript abundance of each gene was contrasted among samples with t-tests. After corrections were made for multiple tests, none of the wheat genes represented on the microarrays showed a statistically significant difference in expression between wheat that has spaceflight exposure in their lineage and plants with no spaceflight exposure. This suggests that exposure to the spaceflight environment in low Earth orbit space stations does not cause significant, heritable changes in gene expression patterns in plants.

Soil and crop management experiments in the Laboratory Biosphere: an analogue system for the Mars on Earth(R) facility

During the years 2002 and 2003, three closed system experiments were carried out in the "Laboratory Biosphere" facility located in Santa Fe, New Mexico. The program involved experimentation of "Hoyt" Soy Beans, (experiment #1) USU Apogee Wheat (experiment #2) and TU-82-155 sweet potato (experiment #3) using a 5.37 m2 soil planting bed which was 30 cm deep. The soil texture, 40% clay, 31% sand and 28% silt (a clay loam), was collected from an organic farm in New Mexico to avoid chemical residues. Soil management practices involved minimal tillage, mulching, returning crop residues to the soil after each experiment and increasing soil biota by introducing worms, soil bacteria and mycorrhizae fungi. High soil pH of the original soil appeared to be a factor affecting the first two experiments. Hence, between experiments #2 and #3, the top 15 cm of the soil was amended using a mix of peat moss, green sand, humates and pumice to improve soil texture, lower soil pH and increase nutrient availability. This resulted in lowering the initial pH of 8.0-6.7 at the start of experiment #3. At the end of the experiment, the pH was 7.6. Soil nitrogen and phosphorus has been adequate, but some chlorosis was evident in the first two experiments. Aphid infestation was the only crop pest problem during the three experiments and was handled using an introduction of Hyppodamia convergens. Experimentation showed there were environmental differences even in this 1200 cubic foot ecological system facility, such as temperature and humidity gradients because of ventilation and airflow patterns which resulted in consequent variations in plant growth and yield. Additional humidifiers were added to counteract low humidity and helped optimize conditions for the sweet potato experiment. The experience and information gained from these experiments are being applied to the future design of the Mars On Earth(R) facility (Silverstone et al., Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base, Advances in Space Research 31(1) (2003) 69-75; Allen and Alling, The design approach for Mars On Earth(R), a biospheric closed system testing facility for long-term space habitation, American Institute of Aeronautics and Astronautics Inc., IAC-02-IAA.8.2.02, 2002).

Crop yield and light/energy efficiency in a closed ecological system: Laboratory Biosphere experiments with wheat and sweet potato

Two crop growth experiments in the soil-based closed ecological facility, Laboratory Biosphere, were conducted from 2003 to 2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted at two densities, 400 and 800 seeds m-2. The lighting regime for the wheat crop was 16 h of light-8 h dark at a total light intensity of around 840 micromoles m-2 s-1 and 48.4 mol m-2 d-1 over 84 days. Average biomass was 1395 g m-2, 16.0 g m-2 d-1 and average seed production was 689 g m-2 and 7.9 g m-2 d-1. The less densely planted side was more productive than the denser planting, with 1634 g m-2 and 18.8 g m-2 d-1 of biomass vs. 1156 g m-2 and 13.3 g m-2 d-1; and a seed harvest of 812.3 g m-2 and 9.3 g m-2 d-1 vs. 566.5 g m-2 and 6.5 g m-2 d-1. Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155 a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 18 h on/6 h dark cycle, totaled 5568 total moles of light per square meter in 126 days for the sweet potatoes, or an average of 44.2 mol m-2 d-1. Temperature regime was 28 +/- 3 degrees C day/22 +/- 4 degrees C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m-2, and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight. Average per day production was 58.7 g m-2 d-1 wet weight and 11.3 g m-2 d-1. For the wheat, average light efficiency was 0.34 g biomass per mole, and 0.17 g seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 1.33 g mol-1 and 0.34 g dry weight of tuber per mole of light. The best area of tuber production had 1.77 g mol-1 wet weight and 0.34 g mol-1 of light dry weight. The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU field results but somewhat below greenhouse trials at comparable light levels, and the best portion of the crop at 0.22 g mol-1 was in-between those values. Sweet potato production was overall close to 50% higher than trials using hydroponic methods with TU-82-155 at NASA JSC. Compared to projected yields for the Mars on Earth life support system, these wheat yields were about 15% higher, and the sweet potato yields averaged over 80% higher.

Atmospheric dynamics in the "Laboratory Biosphere" with wheat and sweet potato crops

Laboratory Biosphere is a 40-m3 closed life system equipped with 12,000 W of high pressure sodium lamps over planting beds with 5.37 m2 of soil. Atmospheric composition changes due to photosynthetic fixation of carbon dioxide and corresponding production of oxygen or the reverse, respiration, are observed in short timeframes, e.g., hourly. To focus on inherent characteristics of the crop as distinct from its area or the volume of the chamber, we report fixation and respiration rates in mmol h-1 m-2 of planted area. An 85-day crop of USU Apogee wheat under a 16-h lighted/8-h dark regime peaked in fixation rate at about 100 mmol h-1 m-2 approximately 24 days after planting. Light intensity was about 840 micromoles m-2 s-1. Dark respiration peaked at about 31 mmol h-1 m-2 at the same time. Thereafter, both fixation and respiration declined toward zero as harvest time approached. A residual soil respiration rate of about 1.9 mmol h-1 m-2 was observed in the dark closed chamber for 100 days after the harvest. A 126-day crop of Tuskegee TU-82-155 sweet potato behaved quite differently. Under a 680 micromoles m-2 s-1, 18-h lighted/6-h dark regime, fixation during lighted hours rose to a plateau ranging from about 27 to 48 mmol h-1 m-2 after 42 days and dark respiration settled into a range of 12-23 mmol h-1 m-2. These rates continued unabated until the harvest at 126 days, suggesting that tuber biomass production might have continued at about the same rate for some time beyond the harvest time that was exercised in this experiment. In both experiments CO2 levels were allowed to range widely from a few hundred to about 3000 ppm, which permitted observation of fixation rates both at varying CO2 concentrations and at each number of days after planting. This enables plotting the fixation rate as a function of both variables. Understanding the atmospheric dynamics of individual crops will be essential for design and atmospheric management of more complex CELSS which integrate the simultaneous growth of several crops as in a sustainable remote life support system.