This is part two of a three-part series on Martian infrastructure. You can read Part One on Martian communications infrastructure here.
You’re an astronaut settling into your first mission on Mars, a less-than-hospitable planet to which human beings are ill-adapted. The atmosphere is over 95 percent carbon dioxide (CO2) and the temperature averages a chilly -81 degrees Fahrenheit. Yet, despite this outright hostile environment, you and your crewmates brought relatively few supplies. Bringing enough food for the whole three-year mission was cost prohibitive. Even considering the dramatically lower launch costs offered by private companies like SpaceX, it might still cost $144 million or more to send three year’s worth of food to Mars for a crew of four (assuming SpaceX’s Falcon Heavy can achieve a launch cost of $3,000 per pound and one astronaut consumes one ton of food per terrestrial year). Instead, you’re equipped with a variety of in-situ resource utilization (ISRU) technologies that will allow you to convert compounds into useful materials and advanced recycling systems that will help ensure nothing is wasted.
data-param-cid="62cec241-7d09-4462-afc2-f72f8d8ef40a"
data-player-id="44f947fb-a5ce-41f1-a4fc-78dcf31c262a"
data-playlist-id=3e5e03f9-7925-4400-8f37-b4daede06b7f
data-elements-player="true"
layout="responsive"
width="16"
height="9"
>
Here on Earth, humans haven’t historically been concerned with waste. The World Bank estimates that the world’s cities will be producing nearly 2.5 billion tons of solid waste annually by 2025. Yet on Mars, where resources are scarce, we’ll be forced to treat seemingly useless materials and byproducts like valuable commodities. Fortunately, NASA has already been perfecting many important recycling and upcycling technologies on the International Space Station (ISS). The objective is to create a closed-loop system in which the outputs of a process can be used as inputs in another process in perpetuity.
On the ISS, for instance, oxygen is produced through electrolysis, a process that uses the electricity generated by the station’s solar arrays to create oxygen and hydrogen from water. This process alone is great for creating breathable air, but it introduces two inefficiencies: it produces excess hydrogen and it consumes water—a resource that’s just as valuable as the oxygen it’s used to produce. In decades past, NASA used the fuel cells that power its space shuttles to produce water. The excess hydrogen along with the CO2 exhaled by the astronauts were then vented into space. As the shuttle program was ending, however, NASA recognized it needed another way to generate H2O. Today, the ISS uses the Sabatier reaction to close the loop. The station’s Sabatier system harnesses the excess hydrogen produced by electrolysis and the CO2 exhaled by the astronauts to create water that’s then purified for consumption. Unfortunately, the Sabatier reaction produces methane, which is vented into space.
Similar processes will be invaluable on Mars, where there is an abundance of carbon dioxide and frozen, possibly liquid, water to use as raw materials. For example, NASA’s Mars Oxygen ISRU Experiment (MOXIE), which is slated to launch aboard the Mars 2020 rover, will demonstrate the use of electrolysis to create oxygen from the CO2 in the Martian atmosphere. Martian water can also be collected and purified for consumption, hygiene, agriculture or used to produce oxygen through the Sabatier reaction, which would in turn produce methane that could be used for fuel or rocket propellent. Alternatively, the water could be split into its constitutive elements to create the liquid hydrogen fuel and oxidizing agents that power many space vehicles today.
Although the Red Planet may eventually boast sophisticated infrastructure for penetrating and mining the Martian regolith—the layer of miscellaneous mineral deposits that coat the surface—resource efficient systems like those mentioned above will be vital until such infrastructure can be erected, tested and perfected. Because, as NASA Principal Technologist for Next Generation Life Support Molly Anderson points out, building and maintaining such systems will be extremely challenging, we don’t want our early explorers to be entirely dependent on resource prospecting.
Recycling systems will also play an important role in ensuring we don’t adulterate the Martian environment with our waste. Unlike the largely controlled ecosystem on the ISS, Martian operations are likely to introduce novel waste streams and new risks of cross-contamination. For example, Martian dust is sure to make its way into human habitats during EVA or extravehicular activities, increasing the importance of ventilation and sanitation and creating additional sources of gaseous and liquid waste. Mars is uninviting enough. It doesn’t need our help to make it more so. “There’s water on Mars, but I still think we’ll be recycling the wastewater,” says Anderson. “There’s no infrastructure to recycle the wastewater on Mars. [On Earth] we use the water and then put our wastewater back into the ground or streams. We don’t want to do that on Mars. Our microbiome goes with us.”
Despite the abundance of Martian resources like CO2 and water, smart resource and waste management are important for efficiency and environmental viability. We ultimately want to make Mars more habitable and more hospitable—a cause that isn’t served by taking the same blasé approach to sustainability and recycling that we’ve historically seen on Earth.
Eventually, Martian resource infrastructure will have to scale. “There’s going to have to be some sort of transport network on the surface to move things between where resources are acquired to where they’re processed and utilized,” notes Anderson. In the meantime, however, it’s our responsibility to envision resource harvesting and distribution systems that are as modular and non-invasive as possible. If we take the opportunity of making human life multi-planetary seriously, we will also take seriously the need to care for the other planets we aim to inhabit. Earth’s infrastructure may be too path dependent to rethink entirely, but Mars is a greenfield, a chance to build outposts and colonies that are models of sustainability and efficiency.
Follow me on Twitter or LinkedIn.