Utilizing Earth's Microbiology to Develop the Framework for a Manufactured Martian Nitrogen Cycle
Date of Award:
Master of Science (MS)
Chemistry and Biochemistry
History has shown us that space travel is a complicated activity not to be taken lightly. Extended missions such as those that would accompany a manned mission to Mars are guaranteed to have increased complexity and require creative solutions to problems we likely take for granted. One such issue is how to supply the necessary amount of nitrogen to the astronauts to keep them alive. Nitrogen is an essential component to life on Earth as most biological molecules, such as protein and DNA, contain a significant amount of it. Most organisms have to get it from what they eat, but some bacteria at the bottom of the food chain are capable of getting it from the air in our atmosphere. These bacteria take nitrogen gas from our atmosphere and convert it into ammonia, which is then taken by plants as they grow and incorporated into their proteins and DNA. As other organisms eat these plants this nitrogen is used to build their cells, furthering the transport through the food chain.
The natural process of converting nitrogen gas to ammonia by bacteria was not sufficient for supplying all of the plant growth as the world's population increases. To address this, an industrial process, known as the Haber-Bosch process, was developed to make artificial fertilizers that are now used from back yard gardens to mega-farms across the globe. Making this type of fertilizer on Mars is not plausible as it requires an extensive infrastructure to support it's production, and shipping the necessary amount of fertilizer would take too much payload. Because nitrogen gas is present on Mars, sending a small supply of bacteria and using as much of the resources on Mars as possible, such as sunlight and water, we may be able to supply the nitrogen for the mission while keeping the payload requirement low. The foundational research necessary to check if this is possible is found in chapter 2 of this thesis. We compared different bacteria and reactor inputs and found that a bacteria, known as Rhodopseu-domonas palustris NIfA*, that uses light as energy and acetate as carbon to produce the highest level of usable nitrogen. This first step of nitrogen fixation is crucial as it allows us to convert the nitrogen gas on mars into biologically relevant nitrogen sources for plant and bacterial growth.
In most ecosystems, the bacteria that supply nitrogen to plants are specific depending on the plant species and the area the bacteria are living. This is problematic as we likely need to provide nitrogen to crop plants with various natural sources of nitrogen. In chapter 3, we show that by using acid to break down the bacteria, we may be able to use a single bacteria to supply nitrogen to various plants. One other aspect of nitrogen on Earth is that there is an extensive system of organisms and reactions that turn the unusable nitrogen in the food chain back into nitrogen gas, creating a cycle. This type of cyclic process is necessary to avoid depleting the nitrogen gas in the atmosphere and for supporting a long-lasting global ecosystem. There is even less nitrogen on Mars, so we want to create a cyclic process there as well. Using mission waste to support bacterial growth and nitrogen recycling would allow us to close the loop and complete an artificial nitrogen cycle.
Valgardson, Kyle, "Utilizing Earth's Microbiology to Develop the Framework for a Manufactured Martian Nitrogen Cycle" (2020). All Graduate Theses and Dissertations. 7930.
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