Universe Today informs cable shields on both Spirit and Opportunity rovers, were made from World Trade Center recycled aluminum. Excerpt below reveals how turn of events made 9/11 Memorial on Mars possible:
"In September of 2001 workers at Honeybee Robotics in lower Manhattan were busy preparing the Rock Abrasion Tools that the twin rovers Spirit and Opportunity would each be equipped with, specialized instruments that would allow scientists to study the interiors of Martian rocks. After the World Trade Center attacks occurred, the company wanted a way to memorialize those who had lost their lives.
Through what was undoubtedly some incredibly skillful use of contacts, Honeybee founder and MER science team member Stephen Gorevan – on a suggestion by JPL engineer Steve Kondos and with help from the NYC mayor’s office and rover mission leader Steve Squyres – was able to procure two pieces of aluminum from the tower debris.
These were fashioned into cylindrical cable shields by a contracted metal shop in Round Rock, Texas, and had American flags adhered to each by Honeybee engineer Tom Myrick.
The image above, taken in 2004, shows the cable shield with American flag on the Rock Abrasion Tool attached to Spirit. At right is an image of the flag shield on Opportunity, acquired on September 11, 2011."