Future Memorials
I hope when we finally set foot on Mars, whoever it is has the forsight to create memorials to out robotic predecessors. Maybe enclose them in some sort of glass casings (it's not like there's plenty of sand around to build the glass). Even though wind may eventually erase the tracks by Sojourner, Spirit and Oppotunity, it would be nice to preserve the entirety of their journeys on the planet.