NASA's Perseverance rover has spent more than 1,645 Martian days on Mars and measured the tiniest dust particles clinging to samples of spacesuit materials aboard the craft. The results were published in the Proceedings of the National Academy of Sciences.
Some of the particles are so small that they can penetrate deep into the lungs and enter the bloodstream. The data will help design spacesuits and habitat modules, develop cleaning methods and set medical standards for the crews of future missions.
Dust was a problem as far back as the Apollo program: it scratched helmet visors, damaged the outer layers of spacesuits and seals, and some astronauts complained of symptoms resembling hay fever. Martian particles are rounder and less abrasive - that is, they wear down surfaces less - but they contain more sulfur, chlorine, iron and silicon than lunar dust, and storms keep them suspended in the atmosphere for long periods.
The rover carries five spacesuit fabric samples measuring 20 by 20 millimeters. They are part of the calibration target of the SHERLOC instrument, mounted on the robotic arm. Dust was also measured by the PIXL instrument, whose target holds samples of Teflon and basaltic glass. Teflon contains no elements that PIXL detects directly, so the signal from it comes from settled dust.
Previous measurements distinguished particles of roughly 3 micrometers and larger. PIXL detected two categories of smaller particles: fine ones, smaller than 2.5 micrometers (a human hair is about 70 micrometers wide), and ultrafine ones, about 100 nanometers, roughly 700 times thinner than a hair. On the Teflon and SHERLOC's Vectran, particles averaged about 2 micrometers, while on the basaltic glass and SHERLOC's Teflon their sizes dropped to 100-300 nanometers.
Adhesion appears to depend on static electricity: dust grains become charged through collisions, and different materials attract particles of different sizes. The smallest ones stayed put for years while the rover drove and drilled. Organic polymers such as Teflon are often used in the outer layers of spacesuits and, as the results showed, readily collect fine dust. Some materials retain it less - this could help in choosing coatings for spacesuits and habitats.
Chemically, the dust matches the iron- and sulfur-rich composition recorded by earlier missions. PIXL also found elevated phosphorus content and signs of calcium sulfate.
On Earth, particles smaller than 2.5 micrometers are linked to negative health effects: they penetrate deep into the lungs and enter the blood. Ultrafine particles no larger than 100 nanometers can travel from the nasal cavity to the brain via the olfactory nerve. Martian dust consists mainly of silicate minerals and carries chemically active compounds, including perchlorates, which can disrupt thyroid function, and reactive iron, which damages cells. The risk depends on the amount of dust and the duration of exposure.
These are the first measurements of fine and ultrafine particles directly on Mars. They could help refine permissible dust levels for astronauts and dust removal methods. NASA is already testing solutions: in March 2025 an electrostatic shield that clears regolith with electric fields was tested on the Moon, and spacesuit components and a hand tool for combating dust are being tested in vacuum chambers in Houston.