Mars City by Asteroid Belt: A Two-Stop Route to Metals

A new arXiv preprint argues a permanent Martian city could be built not from Earth-supplied materials or local Martian ore, but by mining metallic asteroids in the Main Belt and refueling en route to Mars via a two-stop route. A Starship-like craft would first visit an M-type asteroid for metals, then a nearby C-type asteroid for water and propellants (ISPP), before returning to Mars within a 6.4 km/s delta-v capacity, with about 22 asteroid pairs available in a 2040 launch window. The plan could deliver roughly 200 tons of metal over 20 years, but each trip would take about a decade due to orbital timing, and ISPP would fill the 1,100-ton propellant tank at only ~2 kg/day—requiring more than 1,500 years—unless propulsion tech advances. While non-chemical propulsion could change the math, the study concludes asteroid mining is physically feasible yet faces major practical hurdles, ultimately suggesting Mars could host its own space-based industrial backbone rather than a perpetual Earth supply chain.