I think the major concern should be the martians who are
already there , this is why it is a one way trip correct?
they dont want the martians to get their hands on a return trip vehicle that they could use to travel to earth.
after all the martians were stupid enough to destroy their own atmosphere to the point that they had to colonize the earth
in the first place.'
so not having a means of returning to earth may be a really good
choice knowing that the martians obviously were technologically advanced well beyond the earthlings of today.
which means that by now the genetically modified foods that
they were eating has had plenty of time to change the martians
into extremely adaptable beings , they may have even become
something more akin to bacteria over the long span of years.
and when the martians first colonized the earth they may have also
taken precautions to prevent life from earth from reaching mars.
