Perseverance spent 1,645 Martian days watching dust stick to swatches of spacesuit fabric

Over 1,645 Martian days, NASA’s Perseverance rover measured fine and ultrafine dust grains clinging to spacesuit materials and calibration targets mounted on its body, and the finest particles were the ones that stayed. The result, published October 27 in the Proceedings of the National Academy of Sciences, is an early answer to a problem astronauts will face on Mars: a dust that is small enough to be breathed deep into the lungs and that does not shake off.

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The study’s lead author, Scott VanBommel of Washington University in St. Louis, said the smallest particles remain after larger clumps are shaken loose, and that they pose the greatest challenge for human support systems.

Five swatches and two calibration targets

NASA’s release on the study describes five spacesuit material swatches, each 20 millimeters square, mounted on the calibration target of SHERLOC, an instrument on the rover’s arm. An earlier JPL account lists what they are: a piece of polycarbonate helmet visor, Vectran, used on glove palms, two kinds of Teflon, and Ortho-Fabric, a layered cloth containing Nomex, Gore-Tex and Kevlar. Marc Fries, a planetary scientist at NASA’s Johnson Space Center who helped supply the materials, said the swatches are part of preparing for people to eventually go and explore Mars.

Dust data came from two places. The rover’s PIXL instrument, which maps chemistry in rock, carries its own calibration target of Teflon and basaltic glass. Teflon holds no elements PIXL can detect directly, so any elemental signal from that sample comes from dust resting on it. SHERLOC’s target, with its Vectran and Teflon swatches, supplied the second view.

The grains that never let go

The measurement reaches below what earlier missions could resolve. Previous Mars observations resolved dust down to about 3 micrometers, NASA says. PIXL detected fine particles under 2.5 micrometers and ultrafine particles around 100 nanometers. On PIXL’s Teflon target and SHERLOC’s Vectran swatch, particles averaged about 2 micrometers; on PIXL’s basaltic glass and SHERLOC’s Teflon swatch, sizes ranged down to roughly 100 to 300 nanometers.

Static electricity appears to decide which sizes stick to which surfaces. Grains pick up charge as they collide in the air, and different materials attract different grain sizes. Organic polymers such as Teflon readily collect fine dust, the release says, and the finest particles stayed attached through years of driving and drilling. Some materials held less dust than others, which could guide the choice of future suit fabrics and coatings.

The result also complicates a common assumption. Teflon is picked for suits partly because it repels dust, yet on Mars NASA reports that the fine fraction clung to it anyway. The difference may lie in size: a surface that sheds coarse grains can still hold the fine ones.

Why particle size is a health question

On Earth, particles smaller than 2.5 micrometers can penetrate deep into the lungs and enter the bloodstream, a size class tracked by the Environmental Protection Agency under its particulate matter programs. NASA adds that ultrafine particles of about 100 nanometers or less can travel from the nasal cavity to the brain along the olfactory nerve.

Martian dust brings its own chemistry. The release notes that it contains perchlorates, which can disrupt thyroid function, and reactive iron, which can damage cells. The dust itself is rich in iron and sulfur, consistent with earlier missions, and PIXL also found phosphorus enrichment and signs of calcium sulfate. Scientists believe the risk depends on how much dust a person takes in and for how long.

Lindsay Hays, acting director of NASA Headquarters’ Planetary Science Division, said: “Dust has been a surface-exploration challenge since the Apollo program.” Katie Stack Morgan, the Perseverance project scientist at the Jet Propulsion Laboratory, tied the work to the mission’s wider role in preparing for human explorers, alongside the MOXIE oxygen experiment, the Ingenuity helicopter and the spacesuit samples.

What 1,645 Martian days amounts to

A Martian day, or sol, lasts about 24 hours and 40 minutes, so 1,645 of them is roughly 1,690 Earth days, or more than four and a half years of exposure. That duration is the point of the experiment: a lab test cannot easily mimic years of wind, temperature swings, driving vibration and sample drilling. The rover is part of the Mars 2020 mission, and the PIXL hardware that supplied some of the data is described in an arXiv paper on its adaptive sampling.

NASA lists suitports and dual-chamber airlocks among mitigations that would keep dust out of living quarters. The full paper appears in PNAS. What the data cannot yet say is how much of the finest dust a real suit would carry back inside after each outing, and that is the number mission planners most want.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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