Curiosity has been rolling around Mars for over a year now after a successful and daring landing with the aid of a rocket sled. The rover has all sorts of delicate scientific gear that needs to remain in working order for the mission to continue, but did anyone ever stop to think about the wheels? A new image of Curiosity’s undercarriage taken with the Mars Hand Lens Imager shows a hole in in the left rear wheel. Curiosity is pretty far away from the nearest auto garage, but as it turns out, this does not spell doom for the rover.Curiosity has six aluminum wheels, each with a 20-inch diameter. They are designed to grip the dusty Martian terrain, but how can they do that if they’re already falling apart? Much of the rover’s suspension system, including the wheel spokes, are made of titanium. So why was aluminum fine for the wheels? As it turns out, the way Curiosity moves around Mars doesn’t necessitate more durable wheels, which would have only served as excess mass.The word “rover” has a sort of speedy connotation. Some people remember the footage of astronauts driving around the surface of the moon in lunar rovers, but Curiosity takes a much more cautious approach. It creeps along at 1-2 centimeters per second to lessen the chance of an accident. At those speeds, a perfectly round wheel isn’t even necessary. NASA expects that Curiosity’s wheels will become more oval-shaped in time, but no one’s concerned about that. Even if a wheel fell off (which isn’t likely), Curiosity could still trundle around on its titanium spokes.While the just-discovered hole is the most noticeable bit of damage, the left front wheel also shows some signs of wear and tear. On that one we can see deep pock marks and a few small punctures. Curiosity was planned and tested for years before being shipped off to Mars — rest assured no one just forgot to put the good tires on it.