I just rewatched the first season, because of this thread, something I haven't done in years. I thought I'd post my ratings for the 24 season one episodes, subjective of course and YMMV as always. The Catacombs has ratings at
http://www.space1999.net/catacombs/main/ref/epcritic/vxep.html. Their episode guide is at
http://www.space1999.net/catacombs/main/epguide/ty.html. It has a lot of resources including images and transcripts.
I've rated each episode from (0)/worst to (5)/best. Production/episode number is given. The symbol [+] indicates that there was an alien planetary system encountered (even if not landed on); this applies to only 10 of the 24 episodes. The symbol [++] by 6.
Another Time, Another Place is discussed below. Excluding episodes 1 and 6, the remaining 12 episodes,
half the episodes, do not visit an alien world. Rather, there are only weird phenomena, alien visits, encounters with alien probes, ships, or artifacts, etc. I think it's also interesting that the better episodes tend not to visit alien planets.
5. Earthbound (5)
6. Another Time, Another Place (5) [++]
12. Voyager's Return (5)
23. Dragon's Domain (5)
17. War Games (4) [+]
19. The Troubled Spirit (4)
21. The Infernal Machine (4)
22. Mission of the Darians (4)
1. Breakaway (3)
3. Black Sun (3)
14. Death's Other Dominion (3) [+]
16. End of Eternity (3)
2. Matter of Life and Death (2) [+]
11. The Last Sunset (2) [+]
18. The Last Enemy (2) [+]
20. Space Brain (2)
7. Missing Link (1) [+]
8. Guardian of Piri (1) [+]
9. Force of Life (1)
24. The Testament of Arkadia (1) [+]
4. Ring Around the Moon (0)
10. Alpha Child (0)
13. Collision Course (0) [+]
15. The Full Circle (0) [+]
There seems to be some discussion about the fate of the Earth. The newscast from 1.
Breakaway has been mentioned
just upthread. I'll get to episode 6.
Another Time, Another Place in a moment. Besides episodes 1 and 6, the fate of the Earth was mentioned, by my count, in two other episodes: 5.
Earthbound and 22.
Mission of the Darians. From
http://www.space1999.net/catacombs/main/tscript/z05e.html:
KOENIG: "Alan. We're not even sure the Earth still exists. Now, even if it does, our families, those we've loved, won't be there any more."
From
http://www.space1999.net/catacombs/main/tscript/z22motd.html:
NEMAN: "Is it not true that your own planet, Earth, may also no longer exist?"
KOENIG: "It's possible."
[++] Now regarding 6.
Another Time, Another Place. The Earth visited is one of an alternate reality. From
http://www.space1999.net/catacombs/main/tscript/z06atap.html:
[Alternate Reality] VICTOR:
"This is the Earth, "
" but not the world we knew."
"It's an Earth where perhaps we never existed."
"Or perhaps we have yet to be born."
"But apart from us it's empty now. A civilisation once flourished here. Another Atlantis, perhaps. There are relics of them everywhere."
While the possibility is certainly open that that is a view of Earth some time after the Moon was blasted out of orbit, it's also possible that the Earth visited is simply in a completely different timeline altogether.
Finally, as I think has also been mentioned upthread, it seems canonically established in season two's
Journey to Where that the Earth does survive, but it's not in very good shape. That episode also supports the idea that the moon is supposed to be traveling at relativistic speeds. From
http://www.space1999.net/catacombs/main/tscript/z28jtw.html:
TONY: "Yeah, sure. We've been in space for months."
KOENIG: "Which in Earth terms is decades."
Of course, a relative time lapse of decades is not long enough. And, if you think season one is bad....