Before we think about Mars I suggest we should first get our shit together on this little planet.
> I seldom hear "Maybe we should stop making movies until we get our shit together" even though Hollywood has a budget about the same size as NASA's or slightly larger.
People are somewhat free to spend their money on what they choose. Taxes, not so much.
I don't think colonizing other planets in the solar system is a good strategy for giving the human race a second chance because its only a very narrow range of disasters that could wipe out all humans on Earth but spare a colony on Mars.
But there's an incredible amount of science to be gained through more exploration of the solar system. Comparing the atmosphere of Earth to that of Mars and Venus has helped a lot in understanding the details of global warming and ozone depletion. We don't know exactly how fundamental science research is going to pay off but it has before and I'd argue that there is actually something of fundamental value in understanding the universe better.
Research for the purposes of improving life on Earth may be a good use of tax payer dollars.
Establishing a colony is a whole other thing, which implies sustained human existence in a location for the purposes of either species propagation/continuation or resource extraction.
Mining things in space and sending them home to Earth is science fiction nonsense. The energy required means it's fundamentally impossible to have a profitable operation resource extraction from a colony.
I'm not aware of anyone every proposing that people mine minerals on Mars for shipment back to Earth. I have heard people talk about using propellant made on Mars to fuel voyages further out, Zubrin is big on that idea, but that's another kettle of fish - energy and mass can cost different amounts in different places.
People sometimes talk about mining asteroids and bringing the resulting minerals to Earth. I'm not sure that that is economically feasible, at least right now, but it avoids the big problem of having to launch stuff out of Mars's gravity well. Technically speaking the energy involved in getting an asteroid from the main belt to Earth is steeply negative so I don't think you could say that it's impossible on a strictly energy accounting basis, especially since there's no fixed rule establishing the relative value of energy and matter across different technological regimes.
But right now we spend huge amount of energy lofting satellites into orbit around the Earth. If we could use material that was already in space to build satellites in orbit that would be much cheaper from a strictly energy accounting standpoint. That would, of course, require some technological advances but makes a lot of sense if you just look at it in terms of energy.
hold tight to this while it is still true, might not be for much longer :)
The fallacy is that even though both are ostensibly valued in "dollars", at the scale they operate at (society wide), they are not necessarily fungible. You might spend 1 football and get only 0.09 cancer researches. Or they might not be interchangeable at all. I don't have the numbers even to start to make that judgment.
Space is probably just an extreme example of this as it feels "expensive" and seems to directly effect the life of most people very little.
As someone who works in a cancer research-related role, it's nice to not think about work when I leave the office. I would also hazard to guess that many cancer patients enjoy the distraction of various types of entertainment.
Now we can certainly do some refocusing, but I would generally hope that as a civilization and species we can talk and chew gum at the same time.
But more to the point, we're not actually spending any money on terraforming Mars right now. It's just something people talk about. What we are doing is sending robots to Mars to explore. And hopefully at some point we'll be sending better robots or even human scientists who'll want a pre-assembled base put together by robots. Worrying that the terraforming efforts people might get up to in 50 or 100 years will take away from the steps we need to be making now for climate change is premature.
One of the benefits of nuclear weapons is that they make everyone have a significant risk, including the belligerents who traditionally got to hide away, protected and immune. If the people who push the button, so to speak, have options beyond Earth, it makes the prospects much more dim.
That's said, Earth at its worse is still probably infinitely more livable than Mars at its best
Except for taxes. Anybody, who will live on Earth and be above average, will need to support other living beings (humans, animals, fish, forest, grass, birds, insects) with his taxes, otherwise we will have dirty cloak with few billions of angry and hungry living beings, which can dig you out of any bunker.
At Mars, it will be hard to survive without external support for about century, but much lower taxes and self selection of educated people with high IQ can make it booming.
In addition understanding why Mars is a frozen wasteland and why Venus is a molten lead hothouse can lead to revelations about our own climate to help us avoid destroying our own climate.