Lunar Dust is Still One of The Biggest Challenges Facing Moon Exploration

In the coming years, astronauts will be returning to the Moon for the first time since the closing of the Apollo Era. Beyond that, NASA and other space agencies plan to establish the necessary infrastructure to maintain a human presence there. This will include the Artemis Gateway in orbit (formerly the Lunar Gateway) and bases on the surface, like NASA’s Artemis Base Camp and the ESA’s International Moon Village.

This presents a number of challenges. The Moon is an airless body, it experiences extreme variations in temperature, and its surface is exposed to far more radiation than we experience here on Earth. On top of that, there’s the lunar dust (aka. regolith), a fine powder that sticks to everything. To address this particular problem, a team of ESA-led researchers is developing materials that will provide better protection for lunar explorers.

During the Apollo missions, lunar dust was the biggest operational concern for the astronauts. Within a few days of exposure to it, their spacesuits suffered from obscured visors, clogged mechanisms, and erosion in the layers of their suits. This arises from the peculiar nature of lunar regolith, which is jagged, extremely fine, and electrostatically charged (which is what makes it to stick to surfaces).
Microscopic close-up of simulated lunar dust samples (a) EAC-1A, (b) LHS-1 and (c) LMS-1. Credit: ESA

Origins of Moon Dust

Since the Moon is an airless body and experiences no precipitation, regolith on its surface has not had the benefit of geological processes (wind and water erosion) that would smooth it down over time. As a result, billions of years of bombardment from micrometeorites have pulverized much of the surface into fine particles with razor-sharp edges.

Meanwhile, the Sun’s rays (which are not filtered by an atmosphere) impart the dust with a serious static charge. As ESA structural engineer Shumit Das noted in a recent ESA press release:

“Depending on its area of origin the dust might have very different chemical and abrasive characteristics, with its precise properties depending on the selected landing site – which is another factor of concern.

“One of the key findings from Apollo was that the abrasion effects of the lunar regolith would be the major limiting factor in returning to the Moon. We want to overcome that and enable spacesuits that could be used for many more spacewalks than the few performed per Apollo landing – up to 2,500 hours of surface activities is our assumption.”

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith.’ Credit: NASA

Hazardous Material

When the Apollo missions took place, astronauts found that regolith was a constant issue during extra-vehicular activities (EVAs) and also had a very hard time keeping it out of their Apollo Lunar Modules (ALMs). Aside from being hazardous to astronaut’s suits and equipment, lunar regolith also presents a severe hazard to astronaut health.

In a 2005 NASA study, reports from the six Apollo missions were studied to assess the overall effects of lunar dust on EVA systems. In the end, they concluded that the most significant risks included “vision obscuration, false instrument readings, dust coating and contamination, loss of traction, clogging of mechanisms, abrasion, thermal control problems, seal failures, and inhalation and irritation.”

There are also volumes of anecdotal evidence from the Apollo astronauts that indicate how lunar dust was a major hazard during landings. After returning from the Apollo 11 mission, Neil Armstrong described what it was like trying to land the Eagle Lander Module:

“at something less than 100 feet, we were beginning to get a transparent sheet of moving dust that obscured visibility a bit. As we got lower, the visibility continued to decrease.”

Astronaut Buzz Aldrin walks on the surface of the moon near the leg of the lunar module Eagle during the Apollo 11 mission. Credit: NASA

Pete Conrad, the Commander of the Apollo 12 mission, characterized lunar dust in the following way:

“I think probably one of the most aggravating, restricting facets of lunar surface exploration is the dust and its adherence to everything no matter what kind of material, whether it be skin, suit material, metal, no matter what it be and its restrictive friction-like action to everything it gets on.”

“Suit integrities did stay good, but there’s no doubt in my mind that with a couple more EVA’s something could have ground to a halt. In the area where the lunar boots fitted on the suits, we wore through the outer garment and were beginning to wear through the Mylar.”

Lunar regolith is also hazardous to machines, as demonstrated by China’s Yutu-1 rover, which became immobilized on the surface during its second day of operations (Jan. 11th, 2014). While the situation was resolved and the rover kept operating for several more months, Chinese authorities indicated that the rover had “suffered a control circuit malfunction in its driving unit,” which was believed to be the result of dust getting inside.

This image shows a lot of detail of the Yutu rover. Image: Chinese Academy of Sciences/China National Space Administration/The Science and Application Centre for Moon and Deep Space Exploration/Emily Lakdawalla.
This image shows a lot of detail of the Yutu rover. Credit: CAS/CNSA/The Science and Application Center for Moon and Deep Space Exploration/Emily Lakdawalla.

Depending on where the dust comes from on the Moon, it can have very different chemical and abrasive characteristics. Knowing the precise properties of lunar dust i a specific location is therefore essential when it comes to the selection of a landing site. As ESA structural engineer Shumit Das explained:

“One of the key findings from Apollo was that the abrasion effects of the lunar regolith would be the major limiting factor in returning to the Moon. We want to overcome that and enable spacesuits that could be used for many more spacewalks than the few performed per Apollo landing – up to 2 500 hours of surface activities is our assumption.”

Testing New Materials

Drawing their inspiration from the Apollo missions, the ESA has partnered with the French innovation and technology developer Comex, the German Institutes for Textile and Fiber Research, and the citizen science organization the Austrian Space Forum to develop new materials that can withstand the lunar environment. As Malgorzata Holynska, an ESA materials and processes engineer, said in a recent ESA press release:

“The idea came up that as ESA’s going back to the Moon we should look into harnessing the many innovations in the materials field since the Apollo spacesuits were designed, more than half a century ago.”

“So while we are not developing a new spacesuit at this time, we are looking into selecting candidate materials such a suit might use – as well as protective covers for rovers or fixed machinery and infrastructure – and performing some state-of-the-art testing to see how they stand up against simulated lunar conditions, particularly lunar dust.”

Artist’s impression of surface operations on the Moon. Credit: NASA

Last year, the ESA organized a workshop where different materials providers were able to come together discuss possible options based on the most recent advances. Eventually, it was decided that a layered solution needed to be adopted since no one material can do the job alone. The only remaining issues are which combination of functional layers works best and what is the best way to connect them?

“We are then testing these different stacks against criteria contributed by our colleagues from ESA’s Directorate of Robotic and Human Exploration,” added Holynska. “The challenge here is to make the testing as robust as possible, to come up with credible results to guide our choice of trade-offs and down selection.”

The DITF is performing the bulk of project testing. This includes abrasion tests, where a sample of the material is placed in a tumbler with bricks of simulated lunar regolith to see how it handles the physical and chemical interactions. The simulated regolith (called EAC-1A) was created from volcanic soil and was provided by the ESA’s European Astronaut Center in Germany.

Next, there are the customary permeability tests, where high-pressure fluid is applied to samples of material to see if it penetrates the fibers. A thermal cycling test chamber is also in development, which will expose material to extremes in temperature and vacuum conditions. The testing regime is varied so it can examine the entire life cycle of future spacesuits, from being stored to being used for spacewalks. Shumit explains:

“Future suits would typically be stored on the Gateway in lunar orbit between surface EVAs. We need to know that suit seals, rubber or other elements would not be degraded by their time in storage, so that also include accelerated ageing tests, including moisture and radiation exposure.”

Artist’s impression of the Gateway in orbit around the Moon, the Earth hanging in the background. Credit: NASA

In 2024, NASA will be sending astronauts back to the Moon with the Artemis III mission. By 2028, they plan to have finished assembling the Artemis Gateway in orbit and the Artemis Base Camp on the surface, creating a “program for sustainable lunar exploration.” The ESA is a vital partner in these efforts and also plans to build a lunar base that will be a “successor to the ISS.”

In order to spend extended periods of time living, working, and exploring, astronauts will need all the technology, equipment, and infrastructure they need to stay safe in lunar conditions. A key element in all this is the spacesuits that astronauts will wear during EVAs, which will constitute their only protection against the elements and all the natural hazards of the Moon.

This project is being supported through ESA’s Technology Development Element (TDE), a mandatory program that supports all of the ESA’s fields of activity. It was also the subject of a study by Comex researchers that was featured in the journal Advanced Materials Technologies – titled “Advanced Materials for Future Lunar Extravehicular Activity Space Suit

Further Reading: ESA