Revealing mistake: This film was shot in Page Arizona with is pretty far north in the "high country". When they first drive up to the meteor side, there is Saguaro cactus that are only a couple of feet high with huge arms and a neon greenish color. These only grow on the desert floor in Arizona and they certainly are not neon colored. Additionally, the arms don't start appearing until they are much taller as they grow them to balance themselves since they have a very shallow root system.
Revealing mistake: When Harry and Ira take the students to the cave to excavate the meteor, pay attention in the first wide-shot back in the cave where you can see smoke/vapor on the ground. You can see a small patch at the very bottom of the meteor where the smoke is being pumped onto the ground, likely by a concealed smoke-machine either inside of the prop meteor or just underneath the set. You can see the smoke sort-of "churning" unnaturally at the base of the meteor as it is pumped onto the ground, giving away the effect. And to avoid any corrections, yes they say that the area is being adapted by the microbial life the meteor brought to earth and developing a mini-atmosphere in the cave... but this is an unintentionally visible effect. The atmosphere/smoke/vapor wouldn't be all coming from one single tiny spot at the base of the meteor, and it wouldn't be billowing and churning like smoke being pumped from a smoke machine.