I'm thinking about building some glass structures in the Nether on my friends' SMP server (once 1.6 is released), and haven't spent enough time in SP to determine this for myself since I like to work on the SMP server... so, can Ghast fireballs break glass? I intend to make fully-enclosed structures that are too small for Ghasts to spawn inside of, but I want to make sure that an errant Ghast fireball fired while someone's outside won't end up destroying my structure.
I checked the wiki entry on glass, and it discusses arrows and spider jockey arrows, but nothing about Ghast fireballs.