Surface dust poses a fundamental challenge to extraterrestrial human exploration:
On Mars, this challenge is compounded by regional and global dust cycles that coat sensitive hardware.
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We observe particulates measuring as small as 100 to 200 nm on spacesuit samples and calibration targets. Compositionally, this dust is a phosphorus-, iron-, and sulfur-enriched mafic silicate accumulating on materials analogous to the planned external layers of potential crew systems.
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Human flights to the lunar surface were complicated by the adverse effects of angular and abrasive lunar dust on hardware and astronaut health (1). Lunar dust adhered to the Extravehicular Mobility Units (EMUs) of the crew during Extravehicular Activities (EVAs) on the surface and entered the pressurized Lunar Module at the conclusion of each EVA. Exposure to this dust prompted physiological responses from some Apollo crew members akin to hay fever (2, 3). Moreover, lunar dust also negatively affected hardware by etching surfaces, damaging seals, reducing radiator efficiency, obstructing moving parts, and wearing down EMUs to the point that some approached operational limits as missions concluded (4). Although Martian dust differs fundamentally from lunar dust, shaped by distinct geological histories involving water activity, volcanism, impacts, and atmospheres, it is expected to present analogous mechanical and physiological hazards to future crews, albeit through differing mechanisms and severities (5). Notably, the aeolian activity that rounds Martian particulates renders them markedly less angular and abrasive than lunar agglutinates (6), and several hazards of concern to Apollo crews, including the abrasion of coatings and optical surfaces, have not been observed to a comparable degree over decades of robotic Mars surface operations. Recent Mars surface missions have nonetheless demonstrated detrimental effects of dust on engineering systems, including performance-degrading accumulation on solar arrays (7) and solar radiation sensors (8), as well as physical damage to meteorological wind sensors from blown debris (9). Such effects are largely tractable through established design practice (e.g., dust covers over motors and electronics, validation of mechanisms in dust-laden chamber testing on Earth; 10, 11), reflecting decades of accumulated experience protecting robotic hardware on the Martian surface. No comparable heritage exists for protecting humans from Mars dust, and the fine and ultrafine fractions most relevant to crew health remain the least constrained. Continued characterization of Martian dust is made possible by orbiting and landed spacecraft and is a high priority in preparation for crewed missions to Mars (12).
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The ubiquity of Martian dust, particularly its persistence on vertical surfaces subjected to operational vibrations, presents a critical challenge for crewed surface missions. The reduced Martian gravity extends the atmospheric residence time of fine and ultrafine particles, while their magnetic and electrostatic properties promote adhesion to diverse hardware surfaces. Consequently, the infiltration of fine and ultrafine particulates into pressurized habitats represents a primary contamination risk. This vector necessitates the development of rigorous mitigation plans and containment protocols for both crewed outposts and sample receiving facilities (e.g., ref. 43).
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A growing body of evidence from both orbital and surface missions suggests that Martian dust is chemically reactive, potentially toxic, and likely to induce inflammatory responses in biological systems (e.g., refs. 52 and 53).
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Martian dust may have a distinct morphology from the agglutinate-rich lunar dust due to the active aeolian environment of the Martian surface, and the presence of fine and ultrafine particles raises new concerns for astronaut health during surface missions. First, pulmonary mucus is largely ineffective at clearing particles smaller than PM5 (60). Second, particles smaller than ~PM1, such as those reported herein, can evade respiratory clearance mechanisms and penetrate deeply into tissues and organs typically inaccessible to larger particles (Fig. 4; 61). Third, ultrafine particles can bypass the blood–brain barrier by traveling directly from the nasal cavity to the brain via the olfactory nerve (62). Ultrafine Mars dust is enriched in chemically reactive species and therefore represents a direct pathway for neurotoxicants to accumulate in central nervous system tissues and bloodstream (Fig. 4 and SI Appendix, Table S1). Martian dust may therefore not only accumulate in the lungs but also in the liver, kidneys, and brain, potentially leading to systemic physiological and neurological damage. Long-term exposure to ultrafine particles can lead to the development of lung disease via multiple mechanisms (63).