Alkaline reaction could be trace of superoxide in this lithosol
The superoxide reaction with water proceeds this
2O2- + H20 -. 02 + HO2- + OH-
2HO2- = 2OH- + O2 (slowly)
according to my old inorganic textbook.
So a very small trace of a superoxide could produce the alkaline reaction but the pH would slowly rise with time.
Note, in my book a soil by definition has organic matter and until that is determined the material on Mars is not a soil. A better term would be lithosol. But I guess 'soil' helps to con the public that Mars is somehow like earth and so we could grow asparagus @$#@$. Some one above asked for 6 Phoenixes. Nno thanks - six rovers would return more real science and knowledge in one hour than one month of a Phoenix.