jpegpia26520.width-1320.jpg
NASA is watching five spacecraft material samples as they degrade on the Martian surface. They’re shown in the right panel on the bottom row. Above them are the calibration patches for Perseverance’s SHERLOC instrument. The image on the left shows where they’re located on the rover (yellow circle.) Image Credit: NASA/JPL-Caltech/MSSS
NASA's Perseverance Rover is an ambitious mission. In addition to its day-to-day exploration, the rover carried an experimental rotorcraft and is also caching samples for eventual return to Earth. But there's another aspect to its mission that's hidden in the glare of its headline-generating ambitions. The rover is busy testing five different spacesuit materials.
NASA has ambitions to send humans to Mars one day, but there's an enormous amount of work to be done before that ever comes to pass. Mars is a unique environment, and it's not clear how astronauts will survive and work there. We know a lot about the conditions on Mars after sending many rovers and landers there, but many things that astronauts will need have never been tested there or exposed to Martian conditions. This includes basics like spacesuits.
"We’re preparing for people to eventually go and explore Mars." - Marc Fries, NASA's Johnson Space Center
The Martian surface is exposed to extreme UV radiation, temperature fluctuations, ever-present dust, and other environmental factors. The regolith also contains perchlorates, which are corrosive and toxic. There's no better place to test spacesuit materials. Lab experiments could approximate these conditions, but Perseverance was heading to Mars anyway, giving scientists a rare opportunity to test materials in the conditions they'll actually need to withstand.
"Mars is a really harsh, tough place," said SHERLOC science team member Joby Razzell Hollis of the Natural History Museum in London. "Don’t underestimate that — the radiation in particular is pretty nasty."
NASA is testing five different materials in Mars' harsh conditions:
polycarbonate used in helmet visors,
Two types of Teflon, coated and uncoated,
Ortho-fabric, which is the outermost layer used in spacesuits,
Vectran, a high-performance engineered fibre used in the palms of spacesuit gloves.
The spacesuit samples are mounted near the SHERLOC calibration targets so that they can be monitored easily with the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) and the WATSON camera on the end of Perseverance's robotic arm.
This colour-coded graphic shows where the five materials are used on a prototype spacesuit. Image Credit: NASA
The five samples have been exposed to Mars for four years now, and scientists are studying them in detail to see how they've degraded. The idea is to understand the effective lifetime of these spacesuit materials. The lessons learned will inform the design of Mars spacesuits.
"This is one of the forward-looking aspects of the rover's mission — not just thinking about its current science, but also about what comes next," said planetary scientist Marc Fries of NASA's Johnson Space Center in Houston, who helped provide the spacesuit materials. "We're preparing for people to eventually go and explore Mars."
Vectron is cut-resistant and is used in gloves, Teflon excels at repelling dust, and Polycarbonates are highly resistant to impacts while being transparent. Ortho-fabric is a complex, multi-layered material. It contains Gore-Tex for breathability, Nomex for fire resistance, and Kevlar, which is noted for its strength and used in bullet-proof vests.
Every part of a spacesuit is important, but gloves see the most wear and tear. On the ISS, they're regularly inspected for wear. NASA is even developing an automated glove-inspecting system. Image Credit: NASA.
Avid outdoors people, or people with plastic lawn chairs, understand some of the perils on Mars's surface. The Earth's surface is subjected to only a fraction of the UV that Mars's surface is exposed to, yet the UV radiation can cause plastic to fade and weaken and protective outdoor clothing to do the same.
While Earth's ozone layer protects it from most UV rays, Mars lacks a significant ozone layer. Its CO2-dominated atmosphere can absorb some wavelengths of UV, but lots get through. The powerful UV on the Martian surface accelerates the breakdown of plastics and other materials.
Earth experiences temperature extremes, but they're seasonal or dictated by latitude. On Mars, the temperature shift between night and day is extreme. Astronauts can't change suits when the Sun sets; they need suits that can withstand the extreme changes.
While scientists know all of this, they don't know how rapidly the materials will break down. In the Perseverance samples, 50% of the changes that have occurred so far happened within the first 200 days of the mission. Vectran changed first and appears to be the most vulnerable.
Perseverance isn't working alone in this endeavour. Scientists at NASA's Johnson Space Center will perform their own tests by simulating the carbon dioxide atmosphere, air pressure, and ultraviolet light on the Martian surface inside special chambers with material samples inside. They intend to compare lab results with SHERLOC results and then conduct additional tests, like stretching the samples to see when they break. Brittleness is of particular concern because spacesuit materials like Vectron need to be flexible.
"The fabric materials are designed to be tough but flexible, so they protect astronauts but can bend freely," Fries said. "We want to know the extent to which the fabrics lose their strength and flexibility over time. As the fabrics weaken, they can fray and tear, allowing a spacesuit to leak both heat and air."
If humans ever travel to Mars, it could be a long time from now. Whenever it eventually happens, we're getting closer by the day. There are a host of medical and psychological problems to overcome, but some of the barriers are technological, like spacesuit design. Thanks to tests like this, spacesuit design challenges might be some of the easiest challenges to overcome.
Evan Gough
Evan Gough is a science-loving guy with no formal education who loves Earth, forests, hiking, and heavy music. He's guided by Carl Sagan's quote: "Understanding is a kind of ecstasy."