“Who Goes There?,” Don A. Stuart (John W. Campbell), 1938 – Scientists in Antarctica discover the ship of a crash-landed alien who can mimic their bodies.
Comments: Made into The Thing from Another World (1951) and The Thing (1982). An early entry into the sf themes of doppelgangers and aliens “performing human.” Asimov notes in Before the Golden Age Volume 3 that this story is Campbell’s re-write of “The Brain Stealers of Mars.”
Author: Wikipedia: “John Wood Campbell, Jr. (June 8, 1910 – July 11, 1971) was an influential figure in American science fiction. As editor of Astounding Science Fiction (later called Analog Science Fiction and Fact), from late 1937 until his death, he is generally credited with shaping the so-called Golden Age of Science Fiction.”