currently selling on ebay..is this an error or are they all printed like this?
TARGET MOON #75 card reads MARTIAN AIR BASE on back but on the front it says OUTPOST ON MARS ..

Hmmm.

I think they were all this way for the Topps 1958 "Target: Moon" release and the salmon-back "Space" popsicle release. They're that way in the half-dozen examples I could dig up on the internet. Front/back titles are different, but the same descriptive text is on the back.

However, the 1957 Topps "Space" set had both fronts and backs marked "Outpost on Mars." So the lore that says the 1957 and 1958 cards were "identical" except for the set title is wrong.

There's a lot of sets where front and back titles don't match, sometimes for the whole set, and I tend to use the title on the front when there's a mismatch. (Most images you see on the net are only for the fronts.) If back titles are regularly different within a set and I know about, I try to show both. I'm going to check out this series and see if there are any other examples.

thanks for the reply!

It seems that there were two other "major" changes in the card-back titles, from the earlier "Space" sets (by Topps & A&BC cards) and the later "Target: Moon" (blue and salmon backs). The card front titles are the same for all four series. Some of the front/back differences are very minor.

Changed back titles: Space / Target: Moon

34 - Moon Explorers -- Moon Explorers / Lunar Expedition
51 - Eclipse of the Earth -- Eclipse of the Earth / Eclipse of the Sun
75 - Outpost on Mars -- Outpost on Mars / Martian Air Base


Different front/back titles: All 4 Series

1 - Sputnik 1 -- Sputnik I
6 - Three Stage Rocket -- The Three Stage Rocket
10 - Space Headquarters -- Space Flight Headquarters
12 - Briefing for Spaceflight -- Briefing for Space Flight
15 - Zero Hour! -- Zero Hour
19 - Diagram of Space Ship -- Diagram of Spaceship
24 - If Meteor Hit New York -- If Meteors Hit New York
28 - Sunset on the Earth -- Sunset on Earth
38 - It's Easy - On the Moon! -- It's Easy - On the Moon
46 - Collecting Minerals on Moon -- Collecting Minerals on the Moon
57 - Lunar Air Plant -- Lunar Airplant
59 - Gymnastics on Moon -- Gymnastics on the Moon
64 - Lunar Spaceport -- Lunar Space Port
70 - Refuelling Planet Ship -- Refueling Interplanet Ship
74 - Martian Dust Storm -- Martian Dust Storms
79 - Melting in Sun's Heat -- Melting in the Sun's Heat
81 - Jupiter -- Jupiter's Terrain

again thanks for your research !