Detoxifying and Enriching Martian Soil via Synthetic Biology

[SolarpunkFan]

https://www.nasa.gov/directorates/space ... griculture

Adam Arkin
University of California, Berkeley

Description

Although the theoretical case for space biological engineering is convincing, since recent studies on the use of biology in space showed substantial payload minimization over abiotic approaches even before any engineering, the functioning of these biological technologies has yet to be proven in a space-like environment. We will study such functioning for a synthetic biology architecture that can detoxify the perchlorate in Mars soil and also enrich it with ammonia. Our work will inform a prime deliverable of a comparative assessment with alternate chemical approaches postulated or scoped by NASA, and will clarify the feasibility of utilizing our proposed biotechnology to support manned Mars missions. The two system processes of perchlorate reduction and nitrogen fixation individually exist in biology and, when combined, will potentiate soil-based agriculture (by plants or microbes) on Mars. Our concept architecture is a single model organism that will eventually have both systems that are now separate in different strains of the same species. The advantages of our proposed architecture over current approaches, such as washing out perchlorate to cleanse soil or using hydroponics to grow plants, include a low initialization mass of microbial cells, on- demand cell growth with in situ resources, and the elimination of toxic wastewater. To accomplish our proposed concept architecture, we will investigate two strains of a diverse clade of organisms, Pseudomonas, which includes relevant extremophiles. Pseudomonas stutzeri PDA is a perchlorate reducer that we have previously studied using a method that examines the fitness profiles of organism mutants in several environment conditions to obtain genetic determinants of fitness. Pseudomonas stutzeri is also capable of nitrogen fixation (e.g. strain A1501). Pseudomonas has two advantages that make experiments with it more practical than with other space synthetic biology possibilities like photosynthetic, extremophile cyanobacteria: the use of the same host cloning vectors as the model laboratory organistm Escherichia coli, and a doubling time of an hour, which is much faster than seven hours for a model non-extremophile cyanobacterium and four days for a model extremophile cyanobacterium. We will test an environmentally-relevant Pseudomonas host that, in follow-on work, we expect to refactor for efficient expression, operation, and interfacing to different hosts including Pseudomonad extremophiles, cyanobacteria, and other mission possibilities. Here, we will map perchlorate reduction and nitrogen fixation performance to host physiology and environment variables. Since we have already developed a microbial growth chamber that can apply environment parameters over Mars-relevant ranges, e.g., pressure from 10 kPa, temperature from -60 degrees C to 40 degrees C, light intensities up to 25 klx, UV radiation, and a 95%-3% carbon dioxide-nitrogen atmosphere, we will study how strains PDA and A1501 perform in increasingly Mars-like conditions, and what genetic mechanisms mediate survival, growth and activities in these conditions. By controllably exploring functionality, we will map the most extreme conditions in which our mesophile can survive, grow and perform. We will then identify limitations on these activities, and derive targets for future individual and joint optimization of system operation in parameter ranges that are more like Mars. Our work will enable a techno-economic analysis of performance versus output-generation time, input/nutrient mass needs, necessity of alternate chemical approaches, etc. Our concept will achieve the “promising potential” of biological technologies, identified in the 2015 NASA Technology Roadmap TA 7 as “deserv[ing] sine attention.” Broader impacts include Earth-based bioremediation (e.g., land cleanup near oil wells and toxic spills) and non-arable land enrichment to improve food production to address famines, drought, larger populations, etc.
Last Updated: April 6, 2017
Editor: Loura Hall

Being a fan of the Mars Trilogy, this excites me.

[Esquire]

Now that's a study I'd fund.

[Khaat]

Going out of our way to infect Mars with the flu swimmer's ear, huh? H. G. Wells would find that ironic.

[Sea Skimmer]

I would figure this would be possible, chemical processes are pretty infinite, but without an atmosphere the practical value would be limited, since indoor farming would probably just be all hydroponics and robots by the time we are doing it. Good research to pursue though, because long term we might find a planet a lot closer then Mars is to earth, but still need to do some work on it.

[Simon_Jester]

The ability to convert Martian soil into something you can grow crops in, a la Watney, would still be handy even if you're not planning to terraform the entire planet. Though I suppose hydroponics may just be strictly superior to dirt farming as long as you're limited to farming methods that have to fit in a habitat dome or a tunnel.

[Esquire]

On a slight tangent, does anybody happen to know the ratio at which plants convert CO2 into oxygen?

[madd0ct0r]

ratio to what?

[Sea Skimmer]

The ability to convert Martian soil into something you can grow crops in, a la Watney, would still be handy even if you're not planning to terraform the entire planet. Though I suppose hydroponics may just be strictly superior to dirt farming as long as you're limited to farming methods that have to fit in a habitat dome or a tunnel.

That's kinda the trick, if we've got to hold in your air then everything has to be sealed, which means your dirt advantage is a lot more limited then it would be on earth. Meanwhile since Mars has no rain or wind of note in structural terms you could build things that wouldn't last long on earth as permanent structures. At that point having a hydroponic farm only requires digging a ditch, then laying your habitat tube into it, the bottom half holding water.

For a dirt farm your basically going to do the same thing, but backfill inside the membrane with dirt and installed some kind of drainage at the bottom. Hydroponics needs a lot of water, but the vast majority would be constantly recycled, while water poured into dirt isn't lost it might not be all gotten back any easier.

Does occur to me though that say for potted trees in a habitat city, you would want dirt. But that is space for you, the rockets are hardly the holdup, its the thousands of pieces of enabling technology to make it worth it.