Crossword Puzzle Earth-bound comet, perhaps?

Clue: Earth-bound comet, perhaps?

Boundary between Earth and Hades (RIVERSTYX with 9 letters)
Earth's crust bound by faults (HORST with 5 letters)
Earth/Hades boundary, in Greek myth (STYX with 4 letters)
Earth bound? (ATLAS with 5 letters)
Earth, bound? (ATLAS with 5 letters)
Fogg-bound? (EASTWARD with 8 letters)
Without bound (ENDLESS with 7 letters)
1980 remake of "Down to Earth" (XANADU with 6 letters)
The largest man-made object in orbit around the Earth, with "The" (NTRNTNLSPCSTTN with 14 letters)
Earth: Pref. (GEO with 3 letters)