Final answer:
No mining is currently taking place on Mars, but its composition suggests iron would be the most likely metal to be mined if such activity were to be conducted.
Step-by-step explanation:
As of now, there is no active mining taking place on Mars. However, the terrestrial planets, including Mars, are composed primarily of rocks and metals, with a significant proportion of their mass consisting of iron-nickel or iron-sulfur combinations. The most common silicate minerals of their crusts are made of silicon and oxygen, and the most common metal is iron. Should mining ever occur on Mars, iron would be a likely candidate due to its abundance, as indicated by the planet's similar bulk composition to Earth, which has about one third of its mass consisting of iron or iron compounds. While speculative, the resources of Mars might differ from Earth's gold, helium-3, diamonds, and even those on the reference list such as uranium, bromine, or potassium.