Curiosity rover's wheels seem a bit tired and show signs of wear and tear, as reported for example in this Discovery News article from May 22, 2013. This damage only increased since then and wheels now show large holes. It doesn't look pretty, and since picture tells a thousand words, here's a photograph showing difference in wear and tear between Sol 34 and Sol 488 (Solar days on Mars since the start of the mission) so you can appreciate the extent of the damage for yourself:
Close up and comparison of the gash in the aluminum wheel skin as seen on sol 488 on Dec. 20, 2013 (Source: Discovery News)
This of course got me curious, if wear and tear on aluminum wheel skin is so extensive in under a year and a half (Earth years), why didn't NASA simply use classical car pressure tires? Mars has some atmosphere, so the rover could have a compressor onboard to help control tire pressure at all times, despite Martian days and nights having much larger temperature difference than what we're used to having here on Earth. And some tire designs are good for years in atmosphere with oxygen and used on heavy-duty industrial machinery here on Earth.
So, while admittedly not too knowledgeable on tire technology, I still believe it would be feasible to simply use more conventional technology that has some 100 years of evolution and we trust every day to get us from point A to point B, and perhaps extend it with whatever support technology would be needed to keep them in good health, like a few tire pressure sensors, a compressor with 6 outputs one for each tire and so on. It is possible in automobile industry with current tech to have such automatic tire pressure monitoring and inflation/deflation system (know as Self-inflating Tires, or more technically correct - Central Tire Inflation System or CTIS) work on the go, and use threaded kevlar for outer skin or maybe some other synthetic materials instead of rubber for tire skin and inner tube, so...
What was the reason that NASA decided that Curiosity needs non-conventional, solid metallic tires / tire skin? And, given current rate of wear and tear, how long is the rover estimated to be able to continue driving around? Could this threaten rover's planned longevity?
Update: Damage to the wheels is now apparently much larger than what I initially found through related news articles good 100 Martian days ago. Here's the latest photograph of the left-front wheel of NASA's Curiosity Mars rover showing dents and holes on Sol 490, not even a day old as of the time of this update (red circle around the largest hole is my own addition):
NASA's Curiosity Mars rover showing dents and holes on Sol 490 (Source: NASA Mars Science Laboratory MAHLI Raw Images)
NASA's Mars rover Curiosity acquired this image using its Mars Hand Lens Imager (MAHLI), located on the turret at the end of the rover's robotic arm, on December 22, 2013, Sol 490 of the Mars Science Laboratory Mission, at 13:46:19 UTC.
Looks like Curiosity isn't making the
·--- ·--· ·-·· (JPL) signature Morse code pattern tracks any longer with its wheels in the sand as it navigates the Martian surface. That's a pretty large additional gap there, on top of its designed traction pattern:
Reading the Rover's Tracks (Image Credit: NASA/JPL-Caltech)
The straight lines in Curiosity's zigzag track marks are Morse code for JPL, which is short for NASA's Jet Propulsion Laboratory in Pasadena, Calif., where the rover was built and the mission is managed. The "footprint" is more than an homage to the rover's builders, however. It is an important reference mark that the rover can use to drive more precisely via a system called visual odometry.
The Morse code, imprinted on all six wheels, is:
.-..(L), as indicated in this image.
Quote and image source: NASA JPL / MSL
I wonder what is Curiosity scribbling now on the Martian surface. I hope it's nothing offensive! :)