Portal/Space Ship will still be in your town but will it will take you to SAAB instead of Mars. Which means you cannot get back to Mars Colony. Along with that you will not be able to mine Mars ore from c-map. Make sure you have enough (~12k ) that is needed for SAAM, more the better(for Venus ) and Yes you can get mars ore in SaaB either via SC or 3x3 production building that needs 2x roads.