>>13016754Plenty of lithium in the belt they can mine and bring over, only issue is Sulfur. But if Mars had oceans a billion years and we know for a fact that oceans existed up to 500M years ago, then for anywhere from 1Bn to 500M-300M years ago huge oceans existed on Mars. 500-700M years is a long ass time. Sulfur occurs naturally in the universe, its the 5th most common element on Earth (and thereby is likely to exist in substantial amount on Mars too given that said planet formed from the same accretion disk as Earth did around the Sun). Additionally, sulfur is also found in all kinds of body parts in flora and fauna and sulfur is critical to life itself.
So if life existed on Mars in some period of the ~700M year block of time, then deposits over time would saturate the Martian crust and there would be teratons of sulfur that are likely easily accessible. Enough to sustain and early Mars colony that will eventually evolve into a major Martian city.
Then during this growth period, all we as a species would have to do is find a half a dozen multi-kilometer wide asteroids in the belt, of which there are billions, and an equivalent or greater amount into the Kuiper belt and an even greater amount further out into the Oort Cloud, that contain rich lithium and sulfur deposits and move them over into Martian Lagrange points for mining and refinement operations.
And then use Starship or successor transport infrastructure to bring them down to Mars surface for further exploitation and production OR do it all in orbit, with waste products recycled as best as possible and non-recyclable wastes packaged and launched towards Solar north on an exit vector out of the system.
The grand beauty of space is that its so fucking big that you can take all your trash, compound it into cubic tons of mass, put it on a mass driver and yeet it out of the system. Hell, if you're daring, you can attach ships to it with reaction mass to detach and slowdown to create extra-solar probes.