Maybe 3 stars. Read the other reviews, together they give a valid impression. It is UNEVEN.
Yes the sound started way too soft I had volume at 100. After that the sound was OK and no sudden blasting.
I was actually on the edge of my seat through most of it, but one thing I hate is movies that frustrate or try to build suspense by having people NOT COMMUNICATE with each other, like whole movies about a suitcase mixup, how about LOOK INSIDE IT!?
I think the Mars base would have better lighting, and on the suits, not need to carry a flashlight. When asked "what's going on" nobody just answered A ZOMBIE GOT IN AND IS TRYING TO KILL ME!
Don't they have something that could be used as a deadly weapon anywhere?
And at the end too much mist/smoke I couldn't see what bodies he was seeing. Part of the suspense but too annoying, it's like fake suspense.
I get that they've been up there 6 months and are tired and this is sudden shock and stress but they should have communication w each other as second nature by now, but nobody explains anything to each other.
So overall, the suspense was good but too much gimmick. And the bacteria could have had a more complex or nefarious effect. I thought the end was fine.