Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The correct adjective form of the word 'Mars' is "Martian," as it specifically refers to anything associated with the planet Mars, including its surface features, environment, and imagined inhabitants. The term "Martian" is widely recognized in both scientific and popular contexts, particularly in discussions about extraterrestrial life and explorations of Mars.

Other options provided are not standard in English. "Marslan" and "Marscan" do not appear in reputable sources or scientific literature as established adjectives for Mars. "Martean" could be inferred from "Marte," the name for Mars in various languages, such as Spanish. However, it is not commonly used in English contexts.

In contrast, "Martian" has a clear etymology linked to Mars and is well-entrenched in science fiction and popular culture, often describing life or phenomena occurring on Mars. Thus, it is the most appropriate and widely accepted word to describe anything related to the planet, making "Martian" the correct choice among the options provided.