I have sat through five episodes so far. The plots are pedestrian and thoroughly earthbound despite the potential offered by the exciting scenario of the first mission to Mars. I think the writer(s) may be using the opportunity to angle for a legitimate job on "Coronation Street" or some such soap.
Where has the realism gone? The crew appear to have been selected for their lack of supporting family members. They do not seem to have trained together, or got to know each other before the mission. Is there even a single scientist among the crew and what - if anything - are they doing during the long journey out? The token Brit is by his own admission a total newbie. His contribution so far: he grew salad leaves for Christmas and almost destroyed the mission in the first episode.
Nobody cares about radiation, consumables, orbits, navigation and mid course corrections or plans for arrival in Martian orbit.
And I have no idea where they will land, how long they will stay and what they will do when they get to Mars - - but on present evidence it could be little more than staring up each other's fundaments.... You could have much the same drama set in a mission to ascend to the twentieth floor of a tower block. (It's life Jim but not as we know it...)