If one accepts the chronology of the Lost in Space episodes in the order of their original broadcast, the Robinsons landed on 14 planets over the course of the series. There were four planets visited by the crew of the Jupiter 2 which had names given explicitly in on-screen dialogue:
- Earth (“No Place to Hide,” “Visit to a Hostile Planet,” “Target: Earth”);
- Priplanus (from episode 3, “Island in the Sky” to episode 30, “Blast Off into Space” [it is named by Will in “Return from Outer Space”]);
- Kromah (“Flight into the Future” and the next episode, “Collision of Planets,” [in which it is named]);
- Delta (“The Promised Planet” [genuine or not, this is the name used by the inhabitants]).
Five planets can be given immediately understandable names (based on their inhabitants or purpose):
- The Automated Planet, so called by the Robot in “The Forbidden World” for the planet which they visited in the previous episode, “The Ghost Planet;”
- Gilt Proto’s Planet (“Target: Earth”);
- The Sobrams’ Planet (“The Flaming Planet”);
- The Vegetable Planet (“The Great Vegetable Rebellion”);
- The Junkyard Planet (“Junkyard in Space”).
Only four planets have no name given in dialogue or an easily recognisable descriptive name that can be applied to them, although ‘Hunter’s Moon’ might do well in this respect for the first on the list:
- Unnamed Planet 1 (“Hunter’s Moon,” “The Space Primevals,” “The Space Destructors,” “The Haunted Lighthouse”);
- Unnamed Planet 2 (“Deadliest of the Species,” “A Day at the Zoo,” “Two Weeks in Space,” “Castles in Space,” “The Anti-Matter Man”);
- Unnamed Planet 3 (“Princess of Space,” “The Time Merchant”);
- Unnamed Planet 4 (“Fugitives in Space,” “Space Beauty”).
The planet where the Robinsons spent most of season two could fits into either of the last two categories; it is stated on-screen that it lies within sector 6.30, and can therefore be called the Sector 6.30 Planet. This is the same planet that may be named in “The Games of Gamma 6,” but Gamma 6 might refer to Myko's home world; regardless, Gamma 3 has been coined by fans for this world.
And how about a planet that never was? The name Emerald Planet has also been coined to refer to the planet the Jupiter 2 lands on in “Flight into the Future” based on the colour of the planet from space. However, they are still on that planet in the next episode “Collision of the Planets,” where it is called Kromah by the alien computer despatching the wrecking crew there.
For the sake of completeness, four episodes are set entirely in space, so planet names are not an issue:
- “The Derelict”
- “Wild Adventure”
- “Kidnapped in Space”
- “Space Creature”