According to Doug Burns, who was involved with both products back in the 70s, "Pop Rocks came first, then Space Dust. Both originally owned by General Foods. Space Dust happened because Pop Rocks was made up of the top 25%
(if I remember right) largest crystals when the product was made. Some smart dude decided to market the rest as Space Dust rather than throw it away as they had been doing.
Space Dust became Cosmic Candy due to the Angel Dust scare. There were also articles back then in the Penthose letters about the products as a sex aid!
We brought out a bubblegum product called Incredibubble that lasted for a brief time". Doug was the one responsible for coining the name "Cosmic Candy" to replace the name Space Dust.
According to him, there was also a TV commercial produced that was never aired that featured the three "planet heads" eating Space Dust.
There was a book published about Pop Rocks that I am told mentions Space Dust as well. The book is called "Pop Rocks: The Inside Story of America’s Revolutionary Candy", and
is available directly from the Publisher or from Amazon.
By the way, the image at the left is something I modeled and rendered. Click on the image to check out the full-sized image in my CGI section.
I recently picked up a few packets of vintage Space Dust packets, unopened from 1978. Watch this space for a movie of me trying them out! :-)