Another gentleman loser.
There is also Matt Slepin's Under the Dying Sun, a supplement for Spellcraft & Swordplay. He describes the setting as "a grim Sword & Planet setting, heavily inspired by the work of Leigh Brackett with a dose of the Adult Westerns of the 1950’s and the Spaghetti Westerns of the 1960’s." So not exactly the same vibe as Barsoom, but interesting nonetheless. A free playtest version is available here.