I seem to have missed the post that started the Mars thread, but Elon's a fan of Kim Stanley Robinson's award-winning (Hugo, Nebula) sci-fi Mars Trilogy ("Red Mars", "Green Mars", "Blue Mars"), which assumes large scale terraforming over centuries, including thickening and changing the composition of the atmosphere, now a very thin layer of mostly CO2, through the use of bio-engineered plants, boosting temps through various measures, etc. It also involves lots of autonomous robotic construction machines, often self-replicating, to do most of the mining, processing, construction etc. (and you thought Autopilot was an end in itself
) and various other techs we either don't have yet or are just starting to develop. Initially, habitation is largely underground for protection from radiation, later craters are domed. Well worth the read:
https://en.m.wikipedia.org/wiki/Mars_trilogy
Jeff Bezos is another fan.
BTW, Robinson himself takes a dim view of the "Mars as a lifeboat", idea, and there's also the near certainty that terraforming to the extent required would take thousands if not tens if thousands of years, even assuming the tech existed. Here's an excerpt if an interview he did with Bloomberg - the full interview is behind a paywall:
http://www.parabolicarc.com/2016/10/17/kim-stanley-robinson-musks-mars-scenario-believable/
Somewhat more on-topic for this forum is Robinson's "New York 2140", about NYC transformed into a super Venice thanks to AGCC-caused sea-level rise:
https://en.m.wikipedia.org/wiki/New_York_2140