In order to colonize Mars it seems that a system that could (a) reproduce itself a few times and then (b) seek and collect needed raw materials for those systems which would repeat the cycle. The result is exponential growth. SpaceX and Axiom may get us to Mars but they can't terraform (mars-aform?) a planet with material only shipped from Earth.<p>I've been doing research in self-reproducing systems for a while now. In particular, I've been working with a robot and a 3D printer. This raises many thought experiments, such as how to create a servo motor. The point of the research is to highlight "interesting issues" and uncover interesting facts. For example, a Bridgeport is the only machine that can make all of its own parts (so far).<p>Many interesting ideas arise. For example, certain plants can extract useful elements. To quote (The PDF is behind a Springer paywall and I don't have access...)<p>"On an uranium-mining-influenced area, sunflowers (Helianthus annuus) were grown on a small-scaled plot. Subsamples of sunflowers were harvested 34, 66, 96, 108, 140, and 170 days after sowing. Contents of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Th, U, Zn, and rare earth elements (REEs, La–Lu) were determined in the sunflower shoots, as well as total and bioavailable contents of these 25 elements in the soil taken on the day of sowing and after the last harvest."<p>Another interesting idea is to eliminate screws and screwdrivers by using Japanese joinery techniques on 3D printed parts.<p>If you know of published materials on self-reproducing systems, particularly in hardware, please post a link. Creative ideas are welcome.