The NASA Innovative Advanced Concepts (NIAC) Program nurtures visionary ideas that could transform future NASA missions with the creation of radically better or entirely new aerospace concepts. NIAC funded projects study innovative, technically credible, advanced concepts that could one day “Change the Possible” in aerospace. Here is a NAIC Phase I project proposed by Lynn Rothschild at the NASA Ames Research Center (ARC).
Water is literally the lifeblood of human survival and civilization and is critical for our sustained exploration beyond Earth. Mars has plenty of water to sustain our aspirations in the form of subsurface ice. Unfortunately, it is not clean water because it is contaminated by toxic perchlorates. Perchlorate and chlorate are powerful oxidizers that cause equipment corrosion and are hazardous to human health even at low concentrations. It will be necessary to detoxify Martian water to remove these contaminating solutes before it can be used in propellant production, food production, or human consumption. The scale of anticipated water demand on Mars reveals the shortcomings of traditional water detoxification. The purification approaches currently in use on Earth require either large amounts of consumable materials, high electrical draw, or water pretreatment.
Could we make the perchlorates just vanish? This is the innovative solution we propose here, taking advantage of the reduction of chlorate and perchlorate to chloride and oxygen being thermodynamically favorable, if kinetically slow. This is the promise of our regenerative perchlorate reduction system. It can leverage synthetic biology to take advantage of and improve upon natural perchlorate reducing bacteria. These terrestrial microbes are not directly suitable for off-world use. However, their key genes pcrAB and cld, which catalyze the reduction of perchlorates to chloride and oxygen, have previously been identified and well-studied. This proposal exploits the prior work done studying perchlorate-reducing bacteria by engineering this perchlorate reduction pathway into the spaceflight proven Bacillus subtilis strain 168, under the control of a robust, active promoter. This solution is highly sustainable and scalable. Unlike traditional water purification approaches, it outright eliminates perchlorates rather than filtering them to dump somewhere nearby.
The goal for this Phase I project is to explore whether this approach is feasible through the following objectives.
Engineer the genes PcrAB and cld into B. subtilis 168 under the control of the strong promoter pVeg. Test and quantify the efficacy of perchlorate reduction under the modeled conditions.
Develop B. subtilis strains that secrete the enzymes to test intracellular versus extracellular efficacy.
Carry out a trade study comparing the performance of biological water detoxification from the modified bacteria to traditional engineering approaches in terms of mass, power, and crew time.
Draft a plan to include this technology in human Mars missions. Develop this detoxification biotechnology to facilitate more efficient solutions to natural and particularly industrial terrestrial perchlorate contamination on Earth. It will also promote the potential of using life rather than only industrial solutions to address our environmental problems. This may spur further innovations for other terrestrial environmental challenges such as climate change. The detoxification system will be launched as inert, dried spores stable at room temperature for years.
Following arrival at Mars, spores will be rehydrated and grown in a bioreactor that meets planetary protection standards. Martian water will be processed by the bioreactor to achieve perchlorate reduction. Processed water can then be used as is or further purified as required.