Forget the usual space-opera conventions of tinkling ethereal sound-worlds invaded by ominous dissonances and brassy chords. Instead, divide the class into two or more groups, and compose a piece on the extraterrestrial origins of life. A tiny three-note motif can start in one group and be transformed as it gradually reaches another - growing slowly by attaching extra notes, developing a new rhythm in order to reach escape velocity, changing timbres as it evolves within a new environment. Add different instruments swirling like clouds of gas or meteorites percussively punctuating the texture. It's not Star Wars but it's a lot more scientific.