The tone of science fictionfilms is often a guide to the tone of the times the film was made: other worlds and species are viewed in turn as wonderful, terrifying, threatening, incomprehensible, and childishly benign.
... in their photosynthetic pathway:
CO2 + 2 H2S → CH2O + H2O + 2S
Some of these produce globules of sulfur as a waste product instead of oygen, while others ...