[randallsquared]

There is unlikely to be anything worth bringing back from Mars, physically. I think Mars' biggest export to Earth, if it ever has any, will be entertainment or other information.

But I think humans-off-Earth will never be a large percentage of all people, even after/if people-off-Earth are an overwhelming majority. Meat isn't suited for space.

[stcredzero]

There's plenty which will be worth lifting off the surface of Mars, but not to head back to Earth. Mars gravity is only 38% of Earth's -- low enough that we can build a space elevator there with materials we have had for years. Even without that, it's still much, much cheaper to get to the asteroids and the rest of the Solar System from there.

Mars has a nearly 24 hour day/night cycle and solar flux suitable for growing plants. Mars has also had the same sorts of geologic processes that created many of the mineral deposits on Earth. Basically, Mars is a treasure trove of resources to enable the cost-effective human settlement of the rest of the Solar System.

And the rest of the solar system will get settled. There is simply too much military advantage to be gained from being up there as opposed to down here. Ultimately, the amount of resources and energy that a solar system-wide space-faring civilization will be able to control will be a couple of orders of magnitude larger than what we can easily acquire on Earth. Therefore, some Earthside societies will try to settle Mars and exploit the resources up there, and it's only a matter of time until at least one succeeds.

However, these attempts of Earth societies to colonize space will ultimately fail to create good copies of their parent societies and will instead give rise to an entirely new society, which will generate many new innovations much as the American colonies failed to remain under Britain and eventually gave rise to much of the innovation of the Industrial Revolution.

Whether or not we're mostly made of meat by that time -- I'm not sure how relevant that is, really.

http://baetzler.de/humor/meat_beings.html