Martian soil is good enough to grow asparagus!

The Phoenix lander was launched by NASA in August of 2007 to probe the soil in the frozen polar region of Mars. The spacecraft has the ability to perform chemical analysis of the soil samples collected on site. The preliminary data obtained suggests there is nothing toxic in Martian soil that would preclude it from sustaining life. The Martian soil was found to be a lot more alkaline than expected and, thus, chemically similar to the soil here on Earth. In fact, asparagus, green beans and turnips could be easily grown in it! The soil also makes for a good environment for some species of bacteria to thrive in.

The downside is that Phoenix did not detect any organic carbon, the presence of which is an essential requirement for life.