[aspaviento]

A colony in Mars opens the door to improving space travelling which at the same time opens the door to explore other planets. In a distant future humanity may be able to visit other solar systems and who knows, maybe find other species out there.

[Retric]

Colonizing mars doesn’t particularly help colonize space just mars because space is mostly empty not cold inhospitable planets.

A useful asteroid mining base might eventually let you expand into the Oort cloud and then colonize the rest of the galaxy assuming they could be 100% self sufficient and didn’t need solar power. But even here the hard bits are 99% technology we could develop on earth for other things like fusion power.