The one thing that I can think of which Mars has in abundance and is limited on Earth is plain old real-estate. In a century's time (give or take), being able

The one thing that I can think of which Mars has in abundance and is limited on Earth is plain old real-estate. In a century's time (give or take), being able to build sprawling, cheap (for certain values of cheap), polluting factories without having to worry about poisoning the local rivers or running afoul of environmental regulations might start to look like a decent deal.