It's not clear that it's an interim step exactly. Mars has gravity, earth for radiation shielding and some resources to work with. I don't know exactly what Spa

It's not clear that it's an interim step exactly. Mars has gravity, earth for radiation shielding and some resources to work with. I don't know exactly what SpaceX have in mind for a Mars mission, but I'd be surprised if it wasn't a variant on 'Mars Direct'.