UeRe Yu MiSsInG mAi TrAiNs EnD mAi lOvLi UeI oF wRiTiNg? [Train lvl 0-5]

I am not convinced that fuel production on Mars will run smoothly.
Assuming the Mars lander has the same weight as a Moon lander, you will need 4.7 times the fuel to get back to orbit. From what I've read the most popular concept right now is a full-sized rocket landing, refuelling and flying back to Earth. That will need much more fuel.
Sure, there have been soil samples taken, but so often there are surprises when there is new method of scientific examonation.

Of course, if you cut like all military spending world wide and build a huge spaceship, that flies to Mars, stays in orbit and flies back, fueled for all that from the start, it should work. But that not a couple of billions anymore, that is much more.