Reason 1: It's the very first Italian science fiction film.

Reason 2: It's got asteroids. Nearly every sci-fi film has got #$%^ asteroids! I #$%^ HATE asteroids!

Reason 3: It predates "Deep Impact" and "Armageddon" by forty years. This had to be where they got the idea.

Reason 4: The original title, "La Morte Viene dallo Spazio", translates to "Death Comes from Space".

Reason 5: Mario Bava is misnamed as Mario Baja in the American translation of the opening credits.

https://en.wikipedia.org/wiki/The_Day_the_Sky_Exploded

http://www.imdb.com/title/tt0051951/