Mars Dust Wears Spacesuit Fabric Less Than Moon Grit Did

Swatches of spacesuit material riding on NASA's Perseverance rover show little visible wear after 1,645 Martian days, suggesting Martian dust may be less abrasive than the lunar grit that damaged Apollo gear. ^[1][2]

That is good news for anyone planning to put boots on Mars. It is not the all-clear. The same study found particles so small they cling to surfaces for years, and a chemistry that raises separate questions for suits, habitats and air filters. ^[2]

The work was led by Scott VanBommel of Washington University in St. Louis and published in the Proceedings of the National Academy of Sciences under the title "Fine and ultrafine Martian dust presents additional risks for future crewed missions to Mars." The title tells you where the authors put their emphasis. ^[1][2]

What Apollo learned the hard way

Dust was one of the quiet villains of the Apollo landings. Lunar grains are jagged, and they scratched visors, wore down the outer layers of spacesuits and damaged seals. ^[2]

They also followed the astronauts indoors. Dust carried into the lunar module on suits left some Apollo crew members with symptoms like hay fever. ^[2]

Nobody planning a Mars landing wants to relearn that lesson at 225 million kilometres from the repair shop. Hence a small experiment that was, by NASA's own account, part of the plan from the start.

Five swatches and a calibration target

Perseverance carries five spacesuit-material samples, each three-quarters of an inch square, mounted on the calibration target for its SHERLOC instrument. They were sent to Mars to see how such materials fare on the surface. The target carries Teflon and Vectran swatches, two materials of the kind used in spacesuit outer layers. ^[2]

Researchers looked at the dust that settled on them over 1,645 Martian days. Another instrument, PIXL, supplied measurements of the dust, including which elements it contains. ^[1][2]

The swatches showed little visible wear. The Martian grains were smoother and rounder than the jagged lunar ones, which suggests they may scratch equipment less readily. ^[1][2]

That is an inference from shape and from the absence of damage on small swatches. It is not a controlled head-to-head wear test, and it is not a full suit working on Mars. A swatch that sits on a rover target is not an elbow joint that flexes ten thousand times.

Katie Stack Morgan of NASA said Perseverance was built both to search for signs of ancient microbial life and to help prepare for human explorers, through technology demonstrations and the spacesuit samples among them. ^[2]

The trouble with small

The gentler grains are only part of the picture. PIXL detected fine dust smaller than 2.5 micrometers and ultrafine particles around 100 nanometers. On the samples, particles ran down to roughly 100 to 300 nanometers. ^[2]

For scale, a human hair is tens of thousands of nanometers wide. Particles at that size are small enough to hang in air and to slip into the places filters and seals are meant to protect.

Static electricity appears to decide which particles stick to which materials, according to NASA's account. The finest particles stayed put through years of rover driving and drilling. ^[2]

"The larger clumps, the Martian dust bunnies, get shaken off over time," VanBommel said. "But the smallest particles stay behind, and those are the ones that pose the greatest challenge for human support systems." ^[2]

Dust with a chemistry

The study also looked at what the dust is made of. It was enriched in sulfur, chlorine and iron, and it contained more silica than lunar dust. PIXL detected phosphorus and signs of calcium sulfate. ^[1][2]

The Phys.org account of the study also reports perchlorates and other potentially toxic compounds in the dust. ^[1]

What that means for a human body is not yet known. The study measured dust on rover samples. It did not measure health effects in astronauts. How much ultrafine dust would actually reach a crew, and at what exposure it would matter, depends on how long people stay and how well the hardware keeps the dust out. ^[2]

What it means for the hardware

NASA says the findings could inform spacesuit and habitat design, dust-removal procedures and crew health standards. The agency names two designs that could cut the amount of dust entering living quarters, suitports and dual-chamber airlocks. ^[2]

A suitport lets a crew member climb into a suit that stays mounted on the outside of the habitat, so the dirty suit never comes indoors. A dual-chamber airlock gives dust a buffer zone to be dealt with before the inner door opens. Both are aimed at the Apollo problem of dust riding in on the suit. ^[2]

The result also shifts where the engineering effort goes. If Martian grains are kinder to fabric and visors, designers can spend less worry on scratches and more on the invisible fines that settle on surfaces and drift into air. That is a judgement of this paper's, drawn from the study's findings, not a conclusion the researchers have stated.

The comparison with the Moon deserves a careful reading. Apollo's dust problem was written in scratched visors and worn suits, damage you could see and photograph. Mars may turn out to cause the opposite problem, little damage to see and a good deal of material you cannot.

What still has to be tested

Several basic questions are still open. Nobody yet knows how much wear a full suit would take through repeated movement, cleaning and use in Martian conditions. Which suit and habitat materials or coatings collect the least dust under real mission conditions also remains to be found out. ^[2]

The proposed dust-removal measures, suitports and airlocks included, have yet to prove they keep dust out of crew spaces. And it is not settled whether the apparent difference in abrasiveness holds across more materials and longer exposures than five small swatches can show.

For now Perseverance's squares are still out there, collecting dust and wearing slowly, the closest thing to a field test of Mars dust on suit material that anyone has.