Since Mars is much closer to the Asteroid belt than Earth is, it would take less Delta-v to get to the Asteroid belt and return minerals to Mars. One hypothesis is that the origin of the Moons of Mars (Phobos and Deimos) are actually Asteroid captures from the Asteroid belt. 16 Psyche in the main belt could have over $10,000 Quadrillion Dollars worth of minerals. NASA is planning a mission for October 10, 2023 for the Psyche orbiter to launch and get to the asteroid by August 2029 to study. 511 Davida could have $27 quadrillion Dollars worth of minerals and resources. Using the moon Phobos to launch spacecraft is energetically favorable and a useful location from which to dispatch missions to main belt asteroids. Mining the asteroid belt from Mars and its moons could help in the Colonization of Mars.
