Opportunity's heat shield did serve a second purpose...
... besides keeping the rover from burning up: It also led scientists to find
the first meteorite on Mars, since called Heat Shield Rock.
http://www.jpl.nasa.gov/news/news.cfm?release=2005-018
http://www.space.com/missionlaunches/mars_meteor_050119.html
The landing gear also serve as monuments to the rovers and contain
the names of the people who worked on these Mars explorers as
well as the members of The Planetary Society. To say nothing
of how happy they will make some future astroarchaeologist
some day.