QUESTION: 
Would I be able to make a soil mixture that resembles that of Martian soil?

ANSWER from Mary Urquhart on January 16, 1998:
The soil on Mars is similar to red volcanic soil clays of Hawaii, but you
should be able to make do with what you can find in Florida.  Try starting
with a reddish soil (if available) and sift it to remove any plant bits. 
You can also use crafting clay.  Dry red/yellow clays would be the best. 
You might try dry them in a microwave in addition to sifting them.  Make
sure your final product is dry and dust-like.

Mary Urquhart                                    
Laboratory for Atmospheric and Space Physics  
University of Colorado at Boulder