
Oddly enough the star patterns used in the two sky textures appear ot be what would be seen from earth, with Venus seen in the sky, as well as Orion constellation. Some levels which take place completely indoors and have no skylights have no sky textures at all.

Interestingly if use noclip on indoor levels only stars can be seen in the skybox (meaning that two different skyboxes are used), the stars are only bean to be seen from skylights. Whatever the case, the sky on the "Martian" levels of Doom 64 appears to be simply a starlit background, but the first time you get a chance to get outside the base to see the the Terraformer device, you can make out reddish/brown craggy mountains (shadowed in nightly blue) in the distance (perhaps also indicating the possibility of it being on Mars). If it is set on Mars, it actually could be a reference to the Doom II's manual's story, which offered a different 'escape' for the Marine (Doom II), after he fought the forces of hell at the Mars Base itself. In addition it refers to 'installations' plural in a another seciton which could be a reference to both Phobos and Deimos. The manual discusses it being location of the classified "Doom Episodes" described as a 'space installation' he once saved, and in Nintendo Power, Our Hero mentions he had returned to the location of his 'first mission' (which technically could be Mars as he was stationed there in Doom 1, but Doom II marine was also stationed there as well). It is described to be 'planetary' base twice (though other backstory links it to the moon Phobos (moon)).

Though not mentioned by name, what appears to be Mars Base is visited during the game.

He was sent home from Mars on shore leave only to discover that Earth was invaded after his drop pod landed. No action takes place on Mars itself.Īccording to the backstory the Marine of Doom II stopped an invasion at Mars Base which occurred over the course of a few days.
