Sol 3/Sol 689

One of the biggest problems that NASA has faced is damage to Curiosity's six wheels. Not only are the once-smooth wheels scratched and dented all around, but in the bottom left you can see one of the many holes that has torn open in the aluminum.

Sol 60/Sol 711

Mission scientists' original path involved rockier terrain, meant to increase the diversity of samples the rover had access to. Those rocks (specifically "caprock," a particularly rigid and weather-resistant kind of rock) punctured Curiosity's wheels. The rover's current path, seen here on the right, is littered with sand dunes that have occasionally stalled the robot. The Sol 711 image also shows the massive punctures in one of the robot's middle wheels.

Sol 36/Sol 660

One of the many spots on the rover covered in reddish dirt.

Sol 34/Sol 591

This United States penny from 1909 is part of a series of markings and objects meant to help calibrate the cameras that Curiosity is equipped with.

Sol 32/Sol 674

Plenty of Curiosity's parts are left exposed, and will continue to accumulate dirt throughout the life of the rover.

Sol 14/Sol 653

With the closest carwash 200 million miles away, static parts of the rover like this are doomed to collect Martian dust.

Sol 30/Sol 718

Another calibration area collects dust, and the Jet Propulsion Laboratory logo at the top of the image is almost completely obscured.

Sol 30/Sol 640

The MarsDial sundial also acts as a calibration tool for the cameras. You can also find one of these on both the Spirit and Opportunity rovers that currently reside on Mars.

Sol 84/Sol 613

These two Curiosity "selfies," each made from multiple images from the rover's MAHLI imager, show that the top of the rover (where the navigation cameras are located) has remained in pretty good shape despite the wear elsewhere.

All images courtesy of NASA/JPL