Please do my Martian homework
Jelly, 28 26 25 24 23 bytes

-1 byte thanks to carusocomputing (replace the word thimble with abcdefg)

9ØaḣŒ!s²ḣµs9K€;€”.K;⁷µ€


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How?

Makes a list of all 362880 permutations of the first seven nine letters of the English alphabet abcdefghi, which all have the properties of Martian words and are all distinct, and formats them into an essay using the first 729 words.

9ØaḣŒ!s²ḣµs9K€;€”.K;⁷µ€ - Main link: no arguments
9                       - 9 as x
         µ              - monadic chain separation
 Øa                     - yield lowercase alphabet
   ḣ                    - head to x ("abcdefghi")
    Œ!                  - all permutations (362880 distinct Martian words)
       ²                - square x = 81 
      s                 - split into chunks of length 81 (the paragraphs)
        ḣ               - head to x (get the first 9 paragraphs only)
                     µ€ - monadic chain for €ach (for each chunk:)
          s9            -     split into chunks of length 9 (the sentences)
            K€          -     join with spaces for €each (between words in each sentence)
              ;€        -     concatenate €ach with
                ”.      -         '.' (add a full stop* after each sentence)
                  K     -     join with spaces (add a space between the sentences)
                   ;    -     concatenate with
                    ⁷   -         a line feed
                        - implicit print


* period