Mars: fine particles, big problems

When Neil Armstrong took that famous “small step” on the Moon, no one had fully anticipated the menace of lunar dust. It clung to everything, scratched delicate equipment, and left Apollo astronauts coughing and rubbing their eyes. Now, as NASA and other space agencies set their sights on Mars, researchers are sounding the alarm: the Red Planet’s dust could be far more than just an annoying housekeeping problem. It could be a serious, mission-threatening health hazard.

A recent paper in GeoHealth by Justin L. Wang and colleagues from the Keck School of Medicine at USC, NASA’s Johnson Space Center, the University of Colorado, and UCLA takes a hard look at what Martian dust might do to human bodies, and how we might fight back.

From a distance, Mars looks like a vast, dusty desert. Up close, that dust turns out to be a complex mix of fine-grained particles, oxidizing chemicals, and potentially toxic metals. The average dust particle is only about 3 micrometers wide. These are small enough to slip past the lungs’ natural mucus defenses and lodge deep in the alveoli. Once there, it can trigger inflammation, sneak into the bloodstream, and in some cases, cause lasting organ damage.

And the ingredients? Think chemistry set from a villain’s lair. Martian dust is expected to contain Perchlorates, which can disrupt thyroid function and even cause aplastic anemia, Silica, a well-known cause of silicosis, an incurable lung disease, Nanophase iron oxides and basalt particles, both capable of generating harmful reactive oxygen species, Gypsum and other sulfates, which can irritate lungs, eyes, and skin, and last but not least, trace but dangerous metals like chromium (VI), beryllium, arsenic, and cadmium, each linked to cancers, organ damage, or severe respiratory illness.

Why Mars makes it worse

Long-term missions to Mars stack the odds against astronauts in ways the Moon never did. The trip there and back takes years, so there’s no quick evacuation if someone gets sick. Microgravity already weakens bones, muscles, and immune systems. Solar and cosmic radiation can damage lungs and increase cancer risk. Add toxic dust exposure on top of that, and the risks don’t just add up; they may multiply.

Another challenge: Martian dust is electrically charged. Like lunar dust, it will cling to spacesuits and hitch a ride into habitats after every EVA (that is, extravehicular activity). Once inside, the particles can stay suspended in the air, waiting to be inhaled.

What we’ve learned from Earth

Because we’ve never brought Mars dust back to Earth for study (yet), researchers look to analogues, similar materials on Earth that have been linked to human illness. Coal miners exposed to pyrite-rich dust develop “black lung.” Glass workers inhaling vitreous silica have higher lung cancer rates. Construction workers handling certain clays or metals risk kidney disease, neurological damage, or bone loss. The parallels are unsettling.

Fighting the dust

The authors stress that prevention is the first and best line of defense. This means improved dust filtration inside habitats using multi-stage HEPA filters, magnetic filters for iron-rich particles, and systems that can handle Martian dust storm, self-cleaning spacesuits and dust-repelling airlocks to reduce contamination entering living spaces, and operational changes to minimize dust exposure during EVAs.

When prevention fails, some targeted medical countermeasures could help. For instance, potassium iodide supplements can protect against perchlorate-related thyroid damage, Vitamin C can reduce oxidative damage from chromium, supportive therapies, including oxygen, bronchodilators, corticosteroids, for lung irritation and inflammation, and emergency treatments like gastric lavage or activated charcoal for accidental ingestion of toxic dust.

Still, in deep space, even routine medical care is complicated. Surgery is impractical. Supplies are limited. And some diseases, like silicosis or chronic beryllium disease, have no cure.

Mars Sample Return missions are planned for the 2030s, but design decisions for crewed missions are being made today. As the paper points out, dust toxicity is a mission-critical challenge. A crew member with progressive lung disease in the middle of a two-year round trip could jeopardize both their life and the mission’s success.

And there’s one more wildcard: the possibility that Mars harbors life, past or present. While speculative, any unknown microbial hazard would make dust exposure even riskier.

Lunar missions taught us that space exploration is full of surprises. Martian dust could be one of the biggest and deadliest surprises awaiting the first human explorers on the Red Planet. The good news is that we have decades of research on Earth’s occupational hazards to guide us. The bad news? Mars is a whole new world, and we can’t afford to underestimate it.

If you want to learn more, the original article titled "Potential Health Impacts, Treatments, and Countermeasures of Martian Dust on Future Human Space Exploration" on GeoHealth at https://doi.org/10.1029/2024GH001213