While HPL directly referenced the planet Mars in only one story, Clark Ashton Mars had a whole cycle of stories on the red planet. Boyd Pearson has a great article on http://www.eldritchdark.com where he reviews the story cycles of Clark Ashton Smith. The Mars Cycle had a total of five stores; one is a fragment and another was based on a plot by E. M. Johnson. I have read three of the five stories: Seedling of Mars (also known as The Planet Entity – this is the story based on Johnson’s plot), The Dweller in the Gulf and Vaults of Yoh-Vombis.
The Seedling of Mars is a unique tale of alien invasion where the “Martian” is a form of intelligent plant life.
Both The Dweller in the Gulf and the Vaults of Yoh-Vombis have an “alien-like” feeling to them (Alien in reference to the 1979 movie ALIEN). Both stories take place under the surface of Mars where horrible things await the explorers. Shown below are two of the residents of Mars, who live on the planet’s surface.
The Aihai, surface natives of Mars (artwork by Philip Rice; recursive-occlusion.tumblr.com)
Native fauna of Mars, a Vortlup (artwork by Philip Rice; recursive-occlusion.tumblr.com)
I intend to read the remaining two Mars story of Clark Ashton Smith. I highly recommend the Martian tales, which can be found on http://www.eldritchdark.com. In addition to reading the stories, I also recommend checking out The Double Shadow Podcast, hosted by Phil, Ruth and Tim. They do an excellent job reviewing and discussing Clark Ashton Smith’s stories. Thank you – Fred.