Name That Book

With all the talk of Mars these days, I have thought about the first science fiction novel I remember reading. I was eleven years old and got the book from the school library.

There was, of course, a space ship trip to Mars. I don't recall how many people were initially in the crew. All I remember is the main character.

The Martians were intelligent and friendly, and they were physiologically elephant-like, although not huge. As the story progressed, the Earth man managed, over a long period of time, to adapt to the ways of the Martians and survived quite well, physically and socially. He eventually got back on the space ship to return to Earth. It was while his return flight was being described that we found he had not only adapted, but had transmogrified into an elephant-like Martian creature, while maintaining his human brain.

Anyone else recall this book? I have tried to find it via Google and have failed.

"Footfall" by Larry Niven & Jerry Pournell??

Footfall was published thirty years after I read that book, soooo I'm thinking No.
We're talking 1956. Correcting my math means I was twelve years old, not eleven.

Any of these?
https://en.wikipedia.org/wiki/Mars_in_fiction#1950s_and_early_1960s

I've already looked at that web site. Nothing there. I have no idea when the book was written.

Quote :

Dominant beings
Gigantic nocturnal living beings that eat Martian humanoids. They use their body lights for communication. The book also suggests they have the capacity to distort spacetime.

https://en.wikipedia.org/wiki/No_Man_Friday

Nope. I seem to recall that the phrase "Red Planet" was part of the title. But I can't be sure that's accurate.