Big hole in Curiosity rover wheel.

[GNC Harteveld]

http://mars.jpl.nasa.gov/msl-raw-images/msss/00520/mhli/0520MH0262000000E1_DXXX.jpg

That's what you get from driving over 'rocks'.
All the wheels look pretty beat up for only a 3 km drive.
http://mars.jpl.nasa.gov/msl/multimedia/raw/?s=520&camera=MAHLI

[TigaHawk]

It kinda makes sense to me - it looks like the wheels are made out of a thin cylinder of metal rather than your conventional rubber wheels.

Now take into account the weight of the rover... and that it's moving over rocks.

Generaly when you throw a rock at at a thin piece of metal it will dent. rolling over rocks with those wheels with the weight of the rover i'd expect also to do the same.

tho in this pic - http://mars.jpl.nasa.gov/msl-raw-images/msss/00520/mhli/0520MH0262000000E1_DXXX.jpg what would have punctured the metal?

[GNC Harteveld]

Curiosity weighs 900 kg and gravity of Mars is 38% of that on Earth so on Mars the rover weighs 342 kg, that's 57 kg per wheel. It's not the speed either, apparently the top speed is 4 cm per second.