So, yeah, there is NO fucking reason why they would not be wearing helmets to protect themselves from the atmosphere. I dont give a fuck if its breathable, we had containment space worthy suits for EVAs and other exploration in 19 fucking 70 but in 2100 something having a lightweight, reliable, comfortable surface exploration helmet is a bridge too far? I get the writers needed a vehicle to infect the explorers, but cmon. They could of created some event where one of them HAD to take his helmet off after an accident etc and then they get infected, something.
The next movie is supposedly going to deal with the Engineers so a lot of (shitty?) questions will hopefully be answered.
Lastly....David. I dont even know where to start here. So when he firsts cuts his hair that was a HUGE red herring for his taking Walters place. It was hanging around in the back of my head the whole time and the reveal at the end was still a surprise but it was softened a bit by that very obvious bit of narrative via the haircut. Then you have to ask yourself, why kill Elizabeth? I get it, he needed a human host.....but after she put him "back together" like he was fucking humpty dumpty (which must have took quite a bit of effort and time btw) he just decides to sacrifice her? Did he just do it after being bored?
So this basically comes down to shitty programming. The guys who wrote Davids code did a bad job. For him to be such a reliable AI mission specialist or whatever the fuck you want to call him to devolving into a super cyborg devil psychopath makes little sense other than bad code bro. He was a creator, and taker of life. Brilliant. BUT WHY? He decimated the entire species of engineers....for...what? Revenge? Fun? We wont know until Scotts next movie, sadly.