Good and unexpectedly enjoyable movie, with relatively realistic situations. Characters too have an identity. Yet, the plot has at its base a nonsense flaw: no spare oxygen supply or redundancies on a 2 years mission to Mars; no spare parts; no replacement for the most crucial system on the ship! And the only thing they can come up with is... a rather unlikely solution in face of a mission that is by no means the last resort for mankind! The other self-made proposed solution for it, is also unlikely, since in a desperate condition could have been turned against others.