After listening to the space junk episode, I was thinking that a lot of that junk has brought us a whole lot of understanding of the Universe and science in general. So I thought an episode of the top ten space missions (eg: Voyager, Hubble, WMAP, etc) and of course why they are in the top 10, what science we learned and what shocking revelations etc.

Blah Blah Blah, you get the point.