Skeleton Men of Jupiter is a novella originally published in 1942 in Amazing Stories, the last Barsoom story Edgar Rice Burroughs himself wrote. The plot takes John Carter off Mars entirely and onto Jupiter, kidnapped by the skeleton-thin Morgors, a militaristic species of Jovian humanoids planning a full-scale invasion of Barsoom. Dejah Thoris is also captured in the same operation.
Carter spends the novella escaping captivity, navigating the politically complex Jovian moon system, and gathering intelligence on the Morgor invasion plans before returning home to alert Barsoom. The text was clearly intended as the first part of a larger novel that Burroughs never completed, and it ends on an unresolved cliffhanger. The expansion of the canon beyond Mars itself is unique in the Barsoom sequence. Burroughs would have continued the storyline if his health had allowed. The novella was eventually published with the apocryphal Giant of Mars in the 1964 collection John Carter of Mars. Strange and incomplete but interesting.