Returning to the Moon after half a century, and then to Mars, requires reinventing the wheel, literally.
After all, Mars is too far away to get home if you get a flat tire.
"One thing you don't want to happen to you is a flat tire," says Florent Menego, CEO of French tire manufacturer Michelin.
The harsh conditions on Mars were particularly highlighted by the experience of the unmanned Curiosity rover.
Immediately after it landed in 2012, its six rigid aluminum tires were visibly punctured with holes and undercuts.
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As for the Moon, the goal of the US Artemis missions is to return astronauts there, perhaps by 2027.
Later Artemis missions plan to use a lunar rover to explore the Moon's south pole, starting with Artemis V, currently planned for 2030.
Artemis astronauts will travel much further than their Apollo predecessors, who never ventured more than 1969 kilometers across the lunar surface in six landings between 1972 and 40.
"The goal is to cover 10.000 kilometers in 10 years," says Sylvain Bartet, who runs Michelin's lunar airless tire program in the central French city of Clermont-Ferrand.
"We're not talking about short, weekly durations, we're talking about decades of use," says Dr. Santo Padula, who has a doctorate in materials science and works for NASA as an engineer at the John Glenn Research Center in Cleveland, Ohio.
A big challenge for anyone developing technology for the Moon is the huge temperature ranges.
Since temperatures at the lunar poles can drop below -230 degrees Celsius, that's not far from absolute zero, when atoms stop moving.
That's a problem for tires.
"Without the movement of atoms, it's harder for you to get the material to deform and return to its previous state," says Dr. Padula.
Tires must be able to deform as they go over rocks, and then return to their original shape.
"If we permanently deform the tire, it doesn't spin efficiently, and we have problems with power loss," says Dr. Padula.
The new wheels will also carry much heavier loads than the lightweight rovers that the Apollo astronauts rode in.
Future space missions will need to ride on "larger science platforms and mobile habitats that are getting bigger and bigger," he says.
And that will be an even bigger problem on Mars, where gravity is twice as strong as on the Moon.
The Apollo lunar rovers used tires made of piano wire coated with zinc in a woven mesh, with a range of about 33 kilometers.
Because extreme temperatures and cosmic rays decompose rubber or turn it into brittle glass, metal alloys and high-performance plastics are the main competitors for airless space tires.
"Generally, these wheels use materials made of metal or carbon fiber," says Pietro Baglioni, team leader of the Rosalind Franklin mission at the European Space Agency (ESA), which aims to send its own rover to Mars by 2028.
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A promising material is nitinol, an alloy of nickel and titanium.
"If you put them together, you get a metal that behaves like rubber that can be bent in all these different ways and will always stretch back to its original shape," says Earl Patrick Cole, CEO of Smart Tire.
He calls nitinol's flexible properties "one of the craziest things you'll ever see."
Nitinol is a potentially "revolutionary" material, says Dr. Padula, because the alloy also absorbs and releases energy as it changes states.
It could even have a solution for heating and cooling, he says.
However, Michelin's Bartett thinks a material closer to high-performance plastic would be better suited for tires that have to travel long distances on the Moon.
Bridgestone, meanwhile, took a bio-mimicry approach, modeling the pads on camel feet.
Camels have soft, plump pads on their feet that distribute their weight over a wider surface area, preventing their feet from sinking into loose, sandy soil.
Inspired by this, Bridgestone uses a felt-like material for its tread, while the wheel consists of thin metal spokes that can bend.
This bending distributes the weight of the lunar model over a wider contact area, so it can ride without getting stuck in fragments of rock and dust on the lunar surface.
Michelin and Bridgestone are part of another consortium that, along with California-based Venturi Astrolabe, are presenting their own tire technology to NASA at the John Glenn Center this month.
NASA is expected to make a decision later this year.
It could choose one proposal or adopt elements of several.
Meanwhile, Michelin is testing tires by driving a sample rover on a volcano near Clermont, whose dusty terrain resembles the surface of the moon.
Bridgestone is doing the same on the Tottori sand dunes in western Japan.
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ESA is also exploring the possibility of Europe building its own rover for other missions, says Bartet.
That work could have some useful applications here on Earth.
While pursuing his PhD at the University of Southern California, Dr. Cole joined NASA's Entrepreneurship Program to work on commercializing some of the technologies from the Mars rover's super-elastic rubber.
An early product this year will be nickel-titanium bicycle tires.
At around $150 apiece, these tires are much more expensive than regular ones, but they would be extremely durable.
He also plans to work on durable motorcycle tires this year, designed for areas with rough roads.
Because of all this, his "dream" remains to play a role in humanity's return to the Moon.
"So I can tell the kids, look up there, at the moon," he says.
"Well, Dad's tires are up there."
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