probably i'm just daydreaming, but how about..
1., NASA sends equipment to the mars first
2., when the equip has arrived safely, they send the 1st group of people to the mars
3., they research, explore, do what they're supposed to do to be able to take off with a shuttle, and..
4., when done (or getting insane/bored.. hah) they assemble the equip. from step 1 and launch back home, with the given circumstances thanks to step 3
btw. the assumption about nullgravity->gravity collapse.. people can accomodate to different gravities even after a long time spent in each state. however, the most severe effect is that on earth they let go things which eventually fall on the ground. as they got pretty much used to zero gravity and its advantages of having things just floating around, astronauts even have these side-effects years after coming back home from a weeks-long trip in space, guess what a 8yrs long space trip would do.. hah
