The customised rubber able to hit the Martian road
A key challenge for Mars missions is finding materials able to maintain their properties and performance across a wide range of temperatures. With an atmosphere estimated to be around 150 times thinner than the Earth’s(opens in new window), Mars cannot store heat as effectively, resulting in daily temperature fluctuations of 50-100 °C (depending on the chosen mission landing site). These conditions are especially tricky for rubber, crucial for the tyres or tracks of rovers, enabling faster and further travel, with heavier loads. “On June 4th 2025, the Curiosity rover(opens in new window) recorded daily temperature changes of between -79 and -30 degrees Centigrade(opens in new window). Even in milder Earth fluctuations, car drivers often switch between winter and summer tyres,” notes Rafal Anyszka(opens in new window), coordinator of the RED 4 MARS(opens in new window) project, developer of a rubber able to withstand Martian temperatures. This research was undertaken with the support of the Marie Skłodowska-Curie Actions(opens in new window) programme.
Reinventing the (Martian) wheel
Mars rovers currently run on aluminium – thin-walled wheels to make them lighter, though with a maximum speed of 180 metres per hour. However, while successful for previous rovers, Curiosity is too heavy for aluminium wheels which can’t dissipate energy through ‘damping’ as rubber does – making them cumbersome and unreliable. “Put simply: if we want to carry cargo and crew at speed, we need stress-resistant rubber-wheeled rovers,” says Anyszka from the University of Twente(opens in new window), the project host. The project designed a rubber based on a mixture of two elastomers(opens in new window): silicone rubber, the most elastic, with a glass transition temperature (below which it loses elasticity) of around -125 °C, and butadiene rubber, less elastic but with good mechanical properties and wear resistance. Testing resulted in the best ratio of both for a blend able to retain elasticity at very low temperatures. But a challenge remained: as with water and oil, these elastomers are not thermodynamically miscible, meaning they don’t mix. The solution was to add carbon black filler particles, which adsorb the macromolecules of both rubbers and create a unified structure at the microscopic level. But adding high amounts of fillers also requires the use of processing aids to adjust the viscosity of the compounds. “Processing aids are typically oils, but as rovers are not transported in pressurised containers these can migrate to the rubber’s surface and evaporate into the vacuum, contaminating hardware. So we found an alternative in liquid butadiene rubber,” explains Anyszka. Another hurdle was that the elastomers also require different chemical additives for vulcanisation – a curing process whereby molecules chemically bond, forming a network that reacts elastically to external stress. The team developed a classic sulphur-based system, but using a special grade of silicone rubber with a small amount of unsaturated vinyl groups, reactive with sulfur. The two resultant prototype tyres were subjected to mechanical testing to track any behavioural changes, with both able to maintain their viscoelastic properties across the broadest possible temperature range(opens in new window). “When we measured the likely ageing of our prototypes on Mars, we discovered that at the highest radiation doses they could preserve their mechanical properties for at least 80 000 years – a welcome surprise!” remarks Anyszka.
Additional applications for more Earthly benefits
RED 4 MARS findings contribute directly to the EU’s space strategy for Europe(opens in new window), especially ambitions to foster a more innovative and globally competitive European space sector. While the project’s results are already openly available(opens in new window) and with publications pending, the team is currently looking for partners to explore commercial opportunities. “Our rubber’s low-temperature elasticity makes it perfect for a range of applications, such as polar missions for scientific research or resource exploration. Also, its high wear resistance could replace some current rubber applications, reducing microplastic shedding,” says Anyszka.
