Terraform Sustainability Assessment Framework for Bioregenerative Life Support Systems

In this perspective paper, we raise attention to the lack of methods or data to measure claims of sustainability for bioregenerative life support system designs and propose a method for quantifying sustainability. Even though sustainability is used as a critical mission criterion for deep space exploration, there result is a lack of coherence in the literature with the use of the word sustainability and the application of the criterion. We review a Generalized Resilient Design Framework for quantifying the engineered resilience of any environmental control and life support system and explain how it carries assumptions that do not fit the assumptions of sustainability that come out of environmental science. We explain bioregenerative life support system sustainability in the context of seven theoretical frameworks: a planet with soil, biogeochemical cycles, and ecosystem services provided to humans; human consumption of natural resources as loads and disturbances; supply chains as extensions of natural resources engineering application of; forced and natural cycles; bioregenerative systems as fragmented ecosystems; ecosystems as a network of consumer-resource interactions with critical factors occurring at ecosystem control points; and stability of human consumer resources. We then explain the properties of environmental stability and propose a method of quantifying resistance and resilience that are impacted by disturbances, extend this method to quantifying consistence and persistence that are impacted by feedback from loads. Finally, we propose a Terraform Sustainability Assessment Framework for normalizing the quantified sustainability properties of a bioregenerative life support system using the Earth model to control for variance.

Investigating the Growth of Algae Under Low Atmospheric Pressures for Potential Food and Oxygen Production on Mars

With long-term missions to Mars and beyond that would not allow resupply, a self-sustaining Bioregenerative Life Support System (BLSS) is essential. Algae are promising candidates for BLSS due to their completely edible biomass, fast growth rates and ease of handling. Extremophilic algae such as snow algae and halophilic algae may also be especially suited for a BLSS because of their ability to grow under extreme conditions. However, as indicated from over 50 prior space studies examining algal growth, little is known about the growth of algae at close to Mars-relevant pressures. Here, we explored the potential for five algae species to produce oxygen and food under low-pressure conditions relevant to Mars. These included Chloromonas brevispina, Kremastochrysopsis austriaca, Dunaliella salina, Chlorella vulgaris, and Spirulina plantensis. The cultures were grown in duplicate in a low-pressure growth chamber at 670 ± 20 mbar, 330 ± 20 mbar, 160 ± 20 mbar, and 80 ± 2.5 mbar pressures under continuous light exposure (62–70 μmol m–2 s–1). The atmosphere was evacuated and purged with CO2 after sampling each week. Growth experiments showed that D. salina, C. brevispina, and C. vulgaris were the best candidates to be used for BLSS at low pressure. The highest carrying capacities for each species under low pressure conditions were achieved by D. salina at 160 mbar (30.0 ± 4.6 × 105 cells/ml), followed by C. brevispina at 330 mbar (19.8 ± 0.9 × 105 cells/ml) and C. vulgaris at 160 mbar (13.0 ± 1.5 × 105 cells/ml). C. brevispina, D. salina, and C. vulgaris all also displayed substantial growth at the lowest tested pressure of 80 mbar reaching concentrations of 43.4 ± 2.5 × 104, 15.8 ± 1.3 × 104, and 57.1 ± 4.5 × 104 cells per ml, respectively. These results indicate that these species are promising candidates for the development of a Mars-based BLSS using low pressure (∼200–300 mbar) greenhouses and inflatable structures that have already been conceptualized and designed.

To Other Planets With Upgraded Millennial Kombucha in Rhythms of Sustainability and Health Support

Humankind has entered a new era of space exploration: settlements on other planetary bodies are foreseen in the near future. Advanced technologies are being developed to support the adaptation to extraterrestrial environments and, with a view on the longer term, to support the viability of an independent economy. Biological processes will likely play a key role and lead to the production of life-support consumables, and other commodities, in a way that is cheaper and more sustainable than exclusively abiotic processes. Microbial communities could be used to sustain the crews’ health as well as for the production of consumables, for waste recycling, and for biomining. They can self-renew with little resources from Earth, be highly productive on a per-volume basis, and be highly versatile—all of which will be critical in planetary outposts. Well-defined, semi-open, and stress-resistant microecosystems are particularly promising. An instance of it is kombucha, known worldwide as a microbial association that produces an eponymous, widespread soft drink that could be valuable for sustaining crews’ health or as a synbiotic (i.e., probiotic and prebiotic) after a rational assemblage of defined probiotic bacteria and yeasts with endemic or engineered cellulose producers. Bacterial cellulose products offer a wide spectrum of possible functions, from leather-like to innovative smart materials during long-term missions and future activities in extraterrestrial settlements. Cellulose production by kombucha is zero-waste and could be linked to bioregenerative life support system (BLSS) loops. Another advantage of kombucha lies in its ability to mobilize inorganic ions from rocks, which may help feed BLSS from local resources. Besides outlining those applications and others, we discuss needs for knowledge and other obstacles, among which is the biosafety of microbial producers.

The World Smallest Plants (Wolffia Sp.) as Potential Species for Bioregenerative Life Support Systems in Space

To colonise other planets, self-sufficiency of space missions is mandatory. To date, the most promising technology to support long-duration missions is the bioregenerative life support system (BLSS), in which plants as autotrophs play a crucial role in recycling wastes and producing food and oxygen. We reviewed the scientific literature on duckweed (Lemnaceae) and reported available information on plant biological traits, nutritional features, biomass production, and space applications, especially of the genus Wolffia. Results confirmed that the smallest existing higher plants are the best candidate for space BLSS. We discussed needs for further research before criticalities to be addressed to finalise the adoption of Wolffia species for space missions.

Space Aquaculture: Prospects for Raising Aquatic Vertebrates in a Bioregenerative Life-Support System on a Lunar Base

The presence of a human community on the Moon or on Mars for long-term residence would require setting up a production unit allowing partial or total food autonomy. One of the major objectives of a bioregenerative life-support system is to provide food sources for crewed missions using in situ resources and converting these into the food necessary to sustain life in space. The nutritive quality of aquatic organisms makes them prospective candidates to supplement the nutrients supplied by photosynthetic organisms already studied in the context of space missions. To this end, it is relevant to study the potential of fish to be the first vertebrate reared in the framework of space agriculture. This article investigates the prospects of space aquaculture through an overview of the principal space missions involving fish in low orbit and a detailed presentation of the results to date of the Lunar Hatch program, which is studying the possibility of space aquaculture. A promising avenue is recirculating aquaculture systems and integrated multi-trophic aquaculture, which recycles fish waste to convert it into food. In this sense, the development and application of space aquaculture shares the same objectives with sustainable aquaculture on Earth, and thus could indirectly participate in the preservation of our planet.

Development of Equipment that Uses Far-Red Light to Impose Seed Dormancy in Arabidopsis for Spaceflight

In order to use plants as part of a bioregenerative life support system capable of sustaining long-term human habitation in space, it is critical to understand how plants adapt to the stresses associated with extended growth in spaceflight. Optimally, dormant seeds would be germinated on orbit to divorce the effects of spaceflight from the one-time stresses of launch. At an operational level, it is also important to develop experiment protocols that are flexible in timing so they can adapt to crew schedules and unexpected flight-related delays. Arabidopsis thaliana is widely used for investigating the molecular responses of plants to spaceflight. Here we describe the development of a far-red light seed treatment device that suppresses germination of Arabidopsis seeds for periods of ≥12 weeks. Germination can then be induced when the seeds encounter red light, such as transfer to the illumination from on orbit plant growth hardware. This device allows for up to twelve 10×10 cm square Petri dishes containing seeds on nutrient gel to be irradiated simultaneously. The far-red device is contained within a light-proof fabric tent allowing the user to wrap the Petri dishes in aluminum foil in the dark, preventing room lights from reversing the far-red treatment. Long-term storage of the wrapped plates is accomplished using foil storage bags. The throughput of this device facilitates robust, high-replicate biological experiment design, while providing the long-term pre-experiment storage required for maximum mission flexibility.

Growth and Development of Ecotypes of Arabidopsis thaliana: Preliminary Experiments to Prepare for a Moon Lander Mission

NASA is planning to launch robotic landers to the Moon as part of the Artemis lunar program. We have proposed sending a greenhouse housed in a 1U CubeSat as part of one of these robotic missions. A major issue with these small landers is the limited power resources that do not allow for a narrow temperature range that we had on previous spaceflight missions with plants. Thus, the goal of this project was to extend this temperature range, allowing for greater flexibility in terms of hardware development for growing plants on the Moon. Our working hypothesis was that a mixture of ecotypes of Arabidopsis thaliana from colder and warmer climates would allow us to have successful growth of seedlings. However, our results did not support this hypothesis as a single genotype, Columbia (Col-0), had the best seed germination, growth, and development at the widest temperature range (11–25 °C). Based on results to date, we plan on using the Columbia ecotype, which will allow engineers greater flexibility in designing a thermal system. We plan to establish the parameters of growing plants in the lunar environment, and this goal is important for using plants in a bioregenerative life support system needed for human exploration on the Moon.