It’s a common trope that the away teams really shouldn’t be landing in these planets without any idea what’s down there without an alien style hazmat suit and here we go, another example :) I GUESS they get a pass because they were here before and the effects didn’t happen because they were not here long enough
also really strange they don’t confirm that people were dead? Or try and go back and get their bodies which might have equipment/ com badges /might even be alien (Spock was there and he bleeds green), maybe starfleet shouldn’t be so careless about what they leave behind…