One of the characters doing an EVA in Mars orbit becomes utterly
terrified of seeing Phobos looming so large over him that he panics,
goes out of control, and ends up flying away from the spaceship
to his doom.

While this is of course fictional, I wonder how such sights will affect
future explorers? We may think it will be amazing, but a 20-mile wide
space rock hovering over us in the depths of deep space might invoke
another reaction from someone who is actually there.

Perhaps very realistic VR simulations for astronauts going to Mars and
other worlds might help detect such potential problems. I would
consider a crewmember going off his or her gourd to be far more
dangerous and in many ways far more likely on a deep space mission
than most other dangers such a mission might encounter.