Would you get the hell off the desert Southwest already??
We KNOW Mars doesn't look like the desert Southwest. This was the 1950s, and for all anyone knew, Mars was made of red cheese. You must have shit a brick when you saw "Robinson Crusoe on Mars" for the first time.
Hey, and guess what! VENUS ISN'T COVERED BY OCEANS, EITHER!!!!!
Of course by your standards, having once depicted Venus as such would make Asimov, Heinlein, and countless other SF writers complete idiots since they did not discern this in 1950.