Space mining could provide rare earths, iron, hydrogen, and other in-situ resources for lunar and Martian outposts.

The most expensive aspect of space exploration comes in the form of moving payloads. Every ounce on a rocket requires a fuel increase, resupply missions are expensive, and as astronaut crews – human or robotic – become more independent of Earth, long-term missions become increasingly feasible.

Future astronauts will need to collect and process extraterrestrial resources into breathable air, drinkable water, building materials, fuels, and propellants.

As NASA expands its understanding of available resources and the technologies to utilize them, engineers and architects can better incorporate new designs and capabilities into improved mission concepts and exploration plans to advance efficiency and sustainability.

NASA hopes to construct and supply the Lunar Gateway, a space station assembled in orbit around the Moon supporting communications, feature habitation and research facilities, crew and payload airlocks, and docking ports for visiting spacecraft, including Orion, lunar landers, and logistics resupply craft.

However, the farther humans go into deep space, the more important it will be to generate tools and supplies with local materials, a practice called in-situ resource utilization (ISRU).

The practical use of ISRU is being studied by NASA and others to ensure astronauts and future space explorers can make the best use of materials at hand. Outposts will be fabricating their own infrastructure to refuel vehicles, build base camps, craft replacement parts, and sustain life – eventually using native materials and locally assembled manufacturing processes.

NASA

NASA's first-generation Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) rode along with Perseverance rover and successfully produced 12 grams of oxygen an hour at 98% purity or better from carbon dioxide in the Martian atmosphere by using solid oxide electrolysis.

An abundance of resources

According to lunar geological surveys, the Moon contains water for drinking, growing crops and making rocket fuel; helium for nuclear fusion; and rare earth elements used in a host of modern electronics.

The first definitive discovery of water on the Moon was made in 2008 by the Indian mission Chandrayaan-1, which detected hydroxyl molecules spread across the lunar surface and concentrated at the poles, according to NASA. Water is crucial for life but can also be a source of hydrogen and oxygen, which have additional uses as fuel.

Helium-3 is an isotope of helium that is rare on Earth, but NASA estimates a million metric tons of it exists on the Moon. According to the European Space Agency, this could provide nuclear energy in a fusion reactor without producing dangerous waste.

The 17 rare earth metals can fine-tune light and generate powerful magnetic fields. They are present on the Moon, including scandium, yttrium and the 15 lanthanides, according to research by Boeing. These are key elements in solar panels, rechargeable batteries, lasers, catalysts, electronic components, radiation shielding and magnets in motors and drive trains.

Using available sunlight is the most common form of ISRU and has been employed on spacecraft and by Mars rovers for decades. The International Space Station is equipped with large solar arrays to harness the Sun's energy and generate the power needed to support a continuous crew presence aboard the station since November 2000. The proposed Gateway's power and propulsion element will also use solar arrays.

The Moon also contains titanium, a strong, lightweight metal that makes up to 8% of the regolith. It is abundant in the mare basalts, which are the low, visibly dark spots on the Moon seen from Earth.

The lunar highlands have higher concentrations of aluminum than Earth's crust, as well as calcium which could be used to make silicon-based solar cells, and when combined with water, it produces heat and absorbs carbon dioxide.

A NASA team found evidence that the Moon's subsurface may have higher concentrations of iron than previously thought. Other elements found on the Moon include silicon, gold, silver, mercury, and uranium.

Returning to the Moon

"It's not science fiction, there are resources out there," said Laszlo Kestay, a planetary volcanologist at the USGS Astrogeology Science Center in Flagstaff, Arizona.

"NASA has said that the objective of the Artemis program is to go back to stay," said Kestay. "If you're going to stay, that means building bases ... and there's a constant talk about trying to make rocket fuel from the materials on the Moon."

When the U.S. returns to the Moon with NASA's Artemis program, long-term plans include constructing sustainable infrastructure that will allow the crew to stay on the surface and in orbit for longer periods.

Living and working in deep space for months or years will require a different approach to the life-sustaining elements and critical supplies once readily available on Earth. The more that can be sourced or even created onsite, the better. Studies and experiments are designed to develop a better understanding of what resources are accessible and what technologies will work to process them in order to support that exploration infrastructure.

NASA's Lunar Surface Innovation Initiative is designed to develop and demonstrate technologies to use resources at hand to produce water, fuel, and other necessities, as well as facilitate excavation and construction.

Identification and extraction

While we have learned a lot about water and other volatile resources from past and ongoing missions studying the Moon, Mars, and asteroids, there are still knowledge gaps about the location, form, concentration, and distribution of these resources and how best to extract and process them into usable products.

Angel Abbud-Madrid, director of the Colorado School of Mines' Space Resources Program, explained that the initial focus would be on identifying the location and extractability of water, oxygen and then minerals. Over the next decade, there will be several exploratory missions to the Moon conducting drilling and tests to understand the amount and accessibility of those resources. Like terrestrial mines, exploratory actions are time-consuming, and extraction would not occur for at least another decade.

Despite interest in space mining for elements to use back on Earth, Abbud-Madrid describes the main focus as centering on understanding and using lunar resources to build facilities, equipment, and fuel on the Moon. Mining rare earth elements for export to Earth, for example, is not currently economically attractive. However, they are extremely useful as in-situ resources.

The Lunar Reconnaissance Orbiter has returned the highest-quality images so far and a treasure trove of data that indicates the presence of water ice buried under the lunar regolith at certain locations. NASA is also developing several CubeSat missions (nanosatellites used primarily by universities for research missions, typically in low Earth orbits) specifically aimed at trying to better locate where water ice might be found and how much water ice might be available.

"One advantage is that you do not need much new water for humans, since human waste (urine and sweat) can be recycled and made drinkable again (that is what happens in the International Space Station with up to 98% recovery)," Abbud-Madrid added.

The Lunar Crater Observation and Sensing Satellite mission launched along with the lunar orbiter was directed to impact the lunar surface. The resulting 10-mile plume showed that nearly five percent of the regolith was composed of water, while an additional five percent contained volatiles like methane, ammonia, hydrogen, carbon dioxide, and carbon monoxide.

For Mars exploration, NASA's MOXIE or Mars Oxygen In-Situ Resource Utilization Experiment, has been riding with the Perseverance rover, and the instrument has proved to be a viable technology for astronauts on Mars to produce oxygen for fuel and breathing.

"MOXIE's impressive performance shows that it is feasible to extract oxygen from Mars' atmosphere – oxygen that could help supply breathable air or rocket propellant to future astronauts," said NASA Deputy Administrator Pam Melroy. "Developing technologies that let us use resources on the Moon and Mars is critical to build a long-term lunar presence, create a robust lunar economy, and allow us to support an initial human exploration campaign to Mars."

NASA is developing technologies to excavate regolith-based water deposits from various regions on the Moon, Mars, and asteroids, as well as process, transport, and store these resources – specifically oxygen, water, and methane. The ultimate goal is to advance ISRU system-level technology readiness to provide human mission commodities such as propellants, fuel cell reactants, and life support consumables.

NASA

The 3D-Printed Habitat Challenge was a NASA program competition to build a 3D-printed habitat for deep space exploration, designed to advance the construction technology needed to create sustainable housing solutions for Earth and beyond.

Moon manufacturing

The U.S. Army Corps of Engineers has already made use of in-situ materials to develop structures in the field on Earth.

Through the Additive Construction for Mobile Emplacement project, NASA and the Army have partnered to advance 3D additive construction capabilities, as well as excavation and handling technologies to produce in-situ feedstock from lunar regolith.

NASA's Centennial Challenges with industry partners has established a competition to incentivize the demonstration of 3D printing of a deep space habitat and advance construction technology needed to create locally-sourced housing solutions on Earth and beyond.

NASA and other space agencies are conducting international coordination of lunar polar volatiles exploration to determine their viability as potential resources and to use the Moon as a proving ground for Mars ISRU technologies.

It may be that in the next few generations, future space miners and travelers alike can bring home a little piece of extraterrestrial material labeled "Made on the Moon."