Why sustainability matters for a moon base and beyond

Millions of people worldwide came together in awe when NASA’s Artemis II mission sent four astronauts on a 10-day lunar flyby in April. The first crewed trip outside of Earth’s orbit since 1972 sparked a collective “moon joy”—and served as the prelude to an ambitious new era for human space travel.

NASA’s Artemis IV mission, planned for 2028, will land people on the surface of the moon. Later that same year, Artemis V will begin the construction of a lunar base. NASA’s goal is to establish a semicontinuous human presence on the moon in the early 2030s. The moon base will be a hub for research and a waypoint for eventual missions to Mars. Meanwhile, the Chinese and Russian space agencies are working on their own plans for long-term lunar habitation, though those efforts are much less public.

“We’re going back, and we’re going to stay there,” says Allison Christy, a research chemical engineer at NASA’s Glenn Research Center.

Despite the term often being politicized, sustainability is an important consideration for long-term extraterrestrial outposts. The reasons are less about environmental concerns than about simple resource efficiency. It costs more than $1 million/kg to send cargo to the lunar surface. Each breath of air, each drop of water, and each atom of carbon or oxygen or nitrogen or any other element we launch through space has a price tag.

“Every ounce you take up, you want to be able to fully utilize, because that’s money,” says Jim Green, who served as NASA’s chief scientist from 2018 to 2022. Nothing should be sent to the moon in vain. So to prepare for future missions, scientists are finding ways to reduce, reuse, and recycle the materials astronauts will use on the moon and beyond.

Life-cycle analysis for long-term lunar missions

“There are limits to what we can bring to the moon. Even more limits to what we can bring to Mars,” Christy says. “If we can find ways to create meaningful material either from the stuff that’s there or stuff we know will be available, that’s crucial to human exploration.”

We don’t have enough stuff on the moon yet to support a full-blown recycling scheme, but we need to consider material life cycles early to make sure we are prepared in the future, says Chris Wohl, an engineer at NASA’s Langley Research Center.

In many cases, effective resource use starts by designing objects for longevity. “The more resilient a material is, the longer it’ll be there before it needs to be replaced or recycled,” Wohl says.

The materials that NASA will use to create a moon base must be designed to hold up to microgravity, intense radiation, abrasive lunar dust, and temperature swings from –203 to 54 °C.

Wohl says it’s important to strike a balance between inventing new high-performing materials and relying on existing materials. For example, a few very durable drill bits made with a special ceramic coating may be much less expensive to stock in a lunar base in the long run than a bunch of regular drill bits. But older materials are tried and true, and we already know how to make them well.

Wohl’s big project at the moment is developing dust-resistant ceramic, metallic, and polymer materials. These substances would find use in tools, as building materials, and in anything else with moving parts or joints where dust might get in and muck things up. Wohl and his team simulate the lunar dust here on Earth for their experiments, but he says they have to account for the fact that Virginia is much more humid than the moon and has significantly higher gravity.

Creative approaches to extraterrestrial waste management

Some trash is, of course, inevitable. The International Space Station (ISS) offers some lessons about how to manage waste in space.

Currently, on the ISS, waste management involves bagging trash and sending it off on resupply vehicles at the end of their service lives to burn up as the vehicles enter Earth’s atmosphere. That strategy won’t necessarily fly for a long-term mission to the moon or Mars. “We’re not going to take the crater next to us and make it a dump. We’d rather go into the crater and study how it was made,” Green says. NASA researchers are looking into several solutions, such as compacting garbage into blocks that astronauts can store, jettison into space, or repurpose as radiation shielding.

Another idea is to reuse trash on a molecular level. Polymer scientist Katrina Knauer of the National Laboratory of the Rockies recently started working on designing compostable food-packaging materials that can double as fertilizer for crops. “Not only is this waste management easily done on board a space shuttle, but it can be utilized for terraforming or even internally for growing food on long-term missions,” she says.

In addition to being biodegradable, the polymers must also be nonflammable, nonvolatile, and food safe, with a strong enough barrier against moisture and gas to preserve food for several years. Knauer and her team are working on a system based on polyester amides because they are tough, are chemically tunable, and have nitrogen in the backbone. Those nitrogen atoms could be converted to plant-nourishing nitrogen compounds when the polymer breaks down.

So far, the project is going well, Knauer says: when the researchers put shreds of their compostable polymer into soil with sorghum seedlings, the seedlings grew faster than control plants without fertilizer.

Knauer says the project is a “lovely little case study” removed from many of the things that make circular economies on Earth so difficult. Far fewer people will be living on the moon or Mars than Earth. And the specialized polymers those space travelers use won’t have to be cost competitive with Earth’s commodity plastics. “If four astronauts can’t make a circular economy work, do we have any hope for all of society?” she says.

Making it on the moon: Using biosynthesis to manufacture supplies in space

Building a truly sustained—and sustainable—base on the moon or Mars will require learning how to make stuff on-site rather than shipping everything from Earth.

Traditional chemical synthesis involves solvents and reagents that are too volatile to put on a spacecraft. So scientists are turning to synthetic biology as a potential solution for brewing things such as medicines and polymers using carbon scrubbed from breathing air or recycled from waste (including human waste).

A team at NASA’s Ames Research Center has sent several experiments to the ISS to investigate ways to use engineered yeast to produce vitamins.

“Biosynthesis is really, really cool, because life always finds a way,” Christy says. “It mirrors our pursuit as humans to explore these really extreme, challenging environments.” She’s working with a team at Glenn to engineer materials made from bacterially synthesized polymers, with the goal of devising a fully circular, Earth-independent manufacturing scheme.

The biosynthesized polymers would be thermally, chemically, and bacterially recyclable. So the material that’s sent from Earth on a future lunar mission “is the same one that you can be making 20 years down the road . . . without the need to keep bringing stuff up or generating additional polymer waste that can’t be used anymore,” Christy says.

The Glenn team makes composite materials by mixing the polymers with lunar regolith. Depending on the polymer makeup and how much regolith is added, it’s possible to get a wide range of properties, she says. “These futuristic materials are maybe not so futuristic after all, which is a weird place to be at, but it’s really cool, too.”

Although the project is still largely in the proof-of-concept phase, it has been going well so far, Christy says. Her team is planning to begin experiments soon to simulate space manufacturing. The researchers intend to send some material samples to the ISS later this year to get data on how their biosynthesized composites hold up to the extreme conditions in space.

Langley’s Wohl says the great thing about NASA projects is they bring together so many areas of expertise. “There’s a ton of growth right now in this sector,” he says. “There are so many needs for materials, for new chemistry and technologies to be developed to enable us to do all the things that we want to do.”