in the movie that trip to the MAV to leave Mars is equal to (from what i remember) like the distance from driving from Houston to NY, and he can only travel at so slow a speed that it literally takes him i think it was like 4 or 6 months to do this trip. However in the movie, he is there almost as soon as he sets out.
There are other distance things like this throughout the movie which were just instant in the film. I understand it makes the movie 'faster' but i think they could have done a better job portraying just how long it really took him to get places.
But, awesome movie, gets ya in the feels