On Sol 3658 (yestersol), the Mars Curiosity had a checkup look at its wheels using the arm-mounted MAHLI camera. Those wheels have seen better days, but they're holding up and have many more kilometers of driving left in them.
Fun fact: See the holes in the second image? Those leave marks in the sand and are used to determine distance. They also spell out "JPL" in Morse Code:
.--- J
.--. P
.-.. L
NASA/JPL-Caltech/MSSS/Kevin M. Gill
