MacDonalds on Mars ?
Having said that it may actually be a piece of American or Russian crash debris from one of the many probes that went there and crashed and burned - but where this re-inforced wrapping material fits into the structural descriptions of these lost machines remains to be seen. Perhaps it is a bit of sealant material intended to keep internal probe mechanisms free of dust blown by the Martian storms.
The thing is - we know they are up to stuff - not curious enough to investigate obvious human skulls or dinosaur bones - so maybe the elaborate 'scientific investigation' of this mundane plastic is intended to give the masses the impression that they are leaving no stone unturned in their insatiable curiosity to find out the truth about Mars with the Curiosity Rover.
We wait with baited breath to be underwhelmed with the 'science' from NASA