You know, the atmosphere is very rare. It wouldn't conduct sound too well.
7 seconds sound clip from the The Angry Red Planet movie soundboard.
You can hear this line at 00:29:48 in the Blu-ray version of the movie.
Quote context
[...]
- This crazy silence and lack of movement's gotten us all.
- It doesn't make any sense. Something has got to move.
- What's the matter? Ears twitch?
- I know there's something out there.
- Sure, like the invisible Martian?
- Are you certain the outside mics are on?
- You know, the atmosphere is very rare. It wouldn't conduct sound too well.
- Of course. That might also explain why the plants don't move. No breeze.
- I wonder... Could it be... intentional?
- I know it sounds unreasonable, but it just doesn't seem natural.
- You mean, you think it's controlled?
- What beings could possibly exercise such fantastic control?
[...]