Nobody in the private sector is going to go to Mars without preexisting private property rights. There is no economic incentive to doing so. The public sector may send an expedition, but they won't set up a permanent colony except an Antarctica type science station.
> Nobody in the private sector is going to go to Mars without preexisting private property rights.
As always, your rights to your property only exist insofar as you can keep someone from taking that property from you. Whether or not there's an Outer Space Treaty that would pretend to control such things is irrelevant.
In any event, the rules for Mars are the same as they are for asteroids, comets or even a prime spot in orbit.