Over 1,645 Martian days, NASA’s Perseverance Mars rover measured the fine and ultrafine Martian dust particles found clinging to samples of spacesuit materials that are carried aboard the rover, including particles small enough to penetrate the lungs and enter the bloodstream. The findings are published in the Proceedings of the National Academy of Sciences and could inform spacesuit and habitat design, dust-removal procedures and crew health standards for future NASA missions to Mars.