For secondary use?
First in martian underground cities? Then when old and used up put in their deserts?
http://mars.jpl.nasa.gov/msl-raw-images/msss/00530/mcam/0530ML0021050230203342E01_DXXX.jpg
Old and New !
Nasa url to the newer material in image!
Please compare the newness of the square image that seems very freshly
painted green to the older material all around it.
http://mars.jpl.nasa.gov/msl-raw-images/msss/00950/mcam/0950MR0041750030502064E01_DXXX.jpg
http://mars.jpl.nasa.gov/msl-raw-images/msss/00694/mcam/0694MR0029330000402218E01_DXXX.jpg