"Some Martian dirt has the same basic chemistry as garden soil, a new analysis from the Phoenix lander suggests. The find widens the range of organisms that might be able to live on Mars."
http://space.newscientist.com/article/dn14217-martian-soil-could-grow-turnips-phoenix-finds.html?DCMP=ILC-hmts&nsref=news7_head_dn14217