Since touching down on Mars in August 2012, Curiosity has done some cool stuff. The rover is a 1-ton monstrosity that is roughly the size of a small car. As Curiosity approaches it's 2-year anniversary on the Martian surface, we can see that the rover has already taken a beating from the Red Planet, especially on its wheels. How does such damage affect Curiosity's mission?
The internet loves self portraits of Curiosity standing on the Martian surface, but beyond the aesthetic "booya, I'm here" vibe, these portraits allow scientists to look the rover over for damage.
Less well known are the pictures that Curiosity takes of its important systems, like the wheels. Late last year, this hole cropped up, and it was a little surprising. As Jim Erickson, Curiosity's project manager, said, "We always expected we would get some holes in the wheels as we drove. It's just the magnitude of what we're seeing that was the surprise."
Right now, the damage isn't severe enough to be a hindrance to the rover's mission. Scientists and engineers at JPL are confident that Curiosity will still be able to reach the base of Mount Sharp and complete its mission. Even then, engineers are already being a little careful and troubleshooting ideas in order to make sure the rover keeps going and the damage doesn't get any worse.
Curiosity is exploring a completely new geological area on Mars. While venturing into the unknown, the newest Martian explorer discovered "caprocks." A caprock is a particularly hard rock that is more resistant to weathering. They tend to be sharp and hard, and they can puncture Curiosity's aluminum wheels when the rover crosses over them. Erickson says the JPL team is trying their best to avoid caprocks in an effort to minimize the damage that Curiosity's wheels are going to have to endure. That said, this is a new type of rock so scientists are still learning where it likes to hide.
With the new information, Curiosity's team has been using pictures from the Mars Reconnaissance Orbiter to help them pick a safer path for Curiosity to travel. It might take a little longer to get to Mount Sharp, but at least the rover will get there in one piece (we hope). With the other rovers, most of the wheel damage that was gathered came from distance traveled instead of terrain hazards, Curiosity's designers and mission planners didn't anticipate such terrain hazards for this rover (as no others encountered them), so the amount of damage Curiosity has received is a little troublesome.
Because we love morbid worse case scenarios, what would happen if the worst should come to pass? Basically, one day, the wheel would snap and you'd be left with a broken circle. As the rover moves across the surface, the broken wheel would flop around some and it would expose cables connecting the wheel to the motor. If one of those cables are damaged or broken, that would be very bad.
Even though there is some "wheel anxiety" building at JPL, engineers are building and testing new wheels built (and damaged) like those on Curiosity, as they find new ways of protecting the rover. Erickson is certain that Curiosity will still be able to rove around the surface for many more miles, but only if JPL is cautious and smart about it.