According to the article (probably from Playset Magazine) in this Hake’s listing, the Martian Landing set was originally released in 1972. Marx was in decline throughout the ’70s, and the traditional toy soldier format was displaced by Kenner in 1977. (What’s an action figure but a cross between a toy soldier and a doll?)
The idea of the set and the box art are way cooler than the finished product. It’s just a repackaging of the far superior Operation Moon Base. Pieces/molds used in Martian Landing were used in Marx’s later space-themed sets, including Star Station Seven and Galaxy Command.
(Images via eBay)
2 Warps to Neptune 
Having just finished reading Red Planet, I’m assuming that this playset isn’t about giant Martians, but instead a giant playset about Martians.
You are correct, sir. Excellent clarification.
Appears to be missing the playmat. The mountain was the central piece,appearantly.
Sonovabitch, I had this. I’d forgotten about it till browsing the Marx posts here. Terrific memory triggers on this site… had some great air-to-ground battles with this mountain. It must have been given to me second-hand because of its age (came out 2 years before I was born), but it even had the box. Wish I still had it now, could be worth a pretty penny (too lazy and busy to look it up now).
This is why I love 2W2N.