Jetan, also known as Martian chess, is a chess variant first published in 1922. It was created by Edgar Rice Burroughs as a game played on Barsoom, his fictional version of Mars. The game was introduced in The Chessmen of Mars, the fifth book in the Barsoom series. Its rules are described in Chapter 2 and in the Appendix of the book, with an actual game partly described in Chapter 17.