Why don’t we build a spaceport located on the moon surface first, before sending a mission to mars?
If we want to have a permanent settlement on the red planet we have to start thinking on reducing the time travel to Mars significantly. This time could be reduced by using the low gravity of the Moon and from there launch our future mission to mars. By reducing the time travel the supplies will reach the red planet in a shorter time, the astronauts will not be as much affected by the danger of the radiation, meteorite impact, the loneliness of space, etc.
If we use the low gravity of the Moon we can reach higher speed with the same amount of fuel (used to launch a ship from earth), and maybe using the same rocket propulsion existing today, just accelerating the ship for a longer time until it reaches the speed needed.
I think that this could be better achieved in a three step process. First the crew is launched from earth to the ISS in a ship liked for example Orion. From there the crew takes a space vessel that it’s only been used to transport astronauts from the ISS to the Moon. Finally in the Moon the crew boards a bigger ship that has been assembled on the surface that it will take them to Mars.
This project will cost a lot, so NASA will have to ally with others space agencies, as did with the ISS.