The Martian movie blunder

I really enjoyed The Martian movie, every minute of it! But it's hard to keep the rational side of me to aside, so here is some rant.

One of the biggest blunder in the movie.

Matt getting knocked off by the sand storm in the movie beginning scene.

Mars atmosphere, well, there's actually no atmosphere in Mars from Earth's perspective, the air is so thin, 100 times less denser than Earth's
own. In such conditions it's literally not possible to move huge objects irrespective of the wind speed, but the scene in the movie shows otherwise. Matt gets knocked off by an antenna because of a severe sand storm and goes unconscious.

However, in the climax it's the opposite. Matt escapes the martian atmosphere by modifying the Capsule of another mission's Launch Vehicle. He reduces excess weight by removing the unnecessary instruments and gear which is not necessary for his journey so as to maximize the acceleration into outer space while compensating the less fuel. The important part which he removes is the Capsule's head and covers it with a polythene like layering, without the head it can let in huge amounts of air literally tearing the person inside into pieces, but since it's on Mars, this situation would not arise because of its very thin air.

The first scene and the last scene are the two contradicting sciences involved in the movie. Nevertheless, it is fairly accurate in most other parts.