There are some reports stating that the iron that can be found in Mars can be about 6-30 miles. This is quite a lot. It also helps that there are a lot of other minerals that can be found in Mars. For example, there are some portions that are made of volcanic basalt rock. Mars’ soil can be considered very rich in minerals.
In fact, the soil may be composed of chloride, magnesium, potassium, and so much more. A lot of people are interested in Mars because of the speculations that this is a place that can be inhabited and lived in. Only time can tell if it would show some signs of life again in the future.