John Carter is not the only Earthman on Barsoom (Mars); there is another. This Earthman who appears in "The Master Mind of Mars" is a US Army Captain in World War I. This army captain shares a first name with a mariner who went for a longer than anticipated voyage and a last name with an actor who fought aliens, both with Sigourney Weaver and Tom Cruise (but in different films).
Ulysses Paxton