I'd like to say the Apollo Moon landings but while they were a massive influence, I think it goes further back into the misty childhood memories.
Two things stand out - one was standing out in the backyard with the family watching the faint spots of sundry Sputniks crawl across the sky, informed by local newspapers as to the timings. Imagine, we were actually looking at man-made objects in SPACE!!
The other was standing out in our suburban street one night and seeing a bright light streak across the sky, leaving a greenish-white trail behind. That really fired my imagination and sent me off to the local library to find out all I could about meteors! Don't know why I didn't just Google it!
Cheers -