I know with all the glyph stuff this may be a bit random... but its just too cool not to post: I was browsing through the database at symbols.com when I came across this:
look familiar? What's *very* interesting is this is a symbol for Pluto- didn't Marathon's original plot involve a mission to Pluto? Maybe Bungie got the Mara-logo way back when Marathon was first started... they look up the symbol for Pluto (the then-setting of Marathon) add a line and volia! the darling little symbol we all know and love...