[HarkMamilton]

Humanity is at an incredibly high extinction risk. We have all sorts of incredible new technologies that could, at the very least, knock us back to pre-industrial society. They might just kill us outright.

We've already used all the easily accessible high-energy fuels, so if our current industrial society falls apart, we will probably never build another one.

If we don't get to space now, we will probably never get to space. Then it's only a matter of time until we get hit by an asteroid.

Or we'll just get killed by an engineered supervirus and skip the whole pre-industrial decay phase.

Going into space is our insurance policy.

[bluGill]

Insurance against what? Lets assume a self supporting mars colony today, and that the asteroid hits earth tomorrow making humans extinct. Will the mars colony get off mars in time to avoid their asteroid? It seems to me that we need to get to a few earth like planets before we can assume survival.

[HarkMamilton]

Sure, so we'd better get started.

[ythn]

The assumption is that we will somehow "terraform" Mars so that it will be earthlike before Earth is destroyed.

[srtjstjsj]

why would martian life survive the destruction of earth from extraplanetary impact, which would affect martian orbit?

[freeflight]

Mars is only the spearhead for further stellar and maybe even interstellar colonization, after all, we gotta start somewhere don't we? Once we manage to do Mars, by gaining knowledge, developing technologies and maybe even discovering new resources, we can hedge humanities survival further by applying this experience to colonizing other places in space.

[AshleyGrant]

How would that affect Mars's orbit? The remains of the Earth will keep on orbiting the Sun.

[solarengineer]

Indeed. We'd have to start somewhere, though.

[njarboe]

There is still an amazing amount of coal in the ground. Check out the Powder River Basin in the US which, for one example.

[eropple]

There's a lot of it there, but it's hard to extract without modern technology. There's a little peat (arguably the most accessible type of high-energy fuel) left in the British Isles and Finland, but coal is requiring progressively more and more modern effort to extract.

[Spellman]

While true, it's also crazy expensive to extract.

[njarboe]

Not really. Wikipedia says that the USGS extimates that "At a price of $60/ton, roughly half (48%) of the coal is economic to produce." Current prices are near $10 a ton so only highly mechanized shallow strip mining techniques are profitable. Coal is about as valuable as other bulk earth products like sand and gravel. 19th century techniques could easily mine most of this coal. It is shipping, not extraction, that determines the price of coal at a given point on Earth. Civilization might need to restart near the mines, but there are still many of those places left.

Oil on the other hand. That might be a problem.