Now that Opportunity is dead, and since there are ideas for future human missions to Mars, I wonder if there is a project to collect all our rovers and landers or at least label as historical sites the spots where they are resting.
In this answer to an older question about the lunar rovers, there is a link to a NASA's document with recommendations on what to do with the vehicles and sites. Are there any official documents with the same recommendations on Mars??
And what will happen to non-US landers??