I don't understand why Musk is so focused on a Mars Colony. Why go to all the effort of climbing out of one gravity well just to drop yourself down another? It

I don't understand why Musk is so focused on a Mars Colony. Why go to all the effort of climbing out of one gravity well just to drop yourself down another? It be a lot easier to mine asteroids and build colonies in Earth or solar orbit. And potentially hugely profitable if they choose a platinum-rich asteroid. See further: 'The High Frontier: Human Colonies in Space' by Gerard K. O'Neill 'Mining the Sky' by John S. Lewis