What would openstreetmaps.org for Mars look like?

Openstreetmaps.org allows regular people to help build a map of every place on earth. It is a big editing toolbox that allows you to position roads, paths, buildings, and landmarks. If the same type of tool was available for Mars, what types of features would one place on Mars? Would it be for scientific purposes? Would it be for creating hypothetical cities on Mars? Or would it be a little of both?

If something like this does not already exist, would this make a good space mission activation process proposal, or does it lack a certain novelty which other proposals contain?