John Carter: The Origins Of Science Fiction Adventure: : Classic Books

Mars is sometimes called the Red Planet. ... Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons, and weather. It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.
Beginning with John Carter's return to Barsoom (Mars) after a ten-year hiatus -- separated from his wife Dejah Thoris, his unborn child, and the Red Martian people of the nation of Helium, whom he has adopted as his own -- John Carter materializes in the one place on Barsoom from which nobody is allowed to depart: the Valley Dor, the Barsoomian heaven.