unkadug
Follower of "Saget"The Cult
If you look at overhead view of the building, these "vents" are nowhere near the theaters of the attraction.Why would they construct these huge vents and then theme them and try to hide them? I think this could have been due to the transition from Mission to Mars to Alien Encounter. The use of smoke machines, dissipating the smoke and blowing air effects would require more air intake and thus a need for these vents. Just my hypothesis.
In fact if they had of needed more airflow because of smoke them they would have been contructed so far away that we would never even see them. Simple duct work from the theaters to these vents would have been cost prohibitive and would render them virtually useless.