Mars is on (or above) a wiped out Earth level of difficulty already

Mars is more habitable than Earth would be during an extinction event. After the event the wiped out Earth would certainly be more habitable, but if there aren't any humans available to repopulate...

What extinction event could possibly make Earth less habitable than Mars?

There is a broad range of possible human extinction events, e.g. asteroid impact, large-scale volcanism, viral epidemic, nuclear annihilation, biological warfare, ecological collapse, and autonomous robots [1].

Humans actively monitor and defend against each threat. In the U.S., NASA is committed to detecting asteroids, and recently successfully altered the course of one [2].

I believe we are most powerful to overcome extinction events as a united species on the planet we’ve evolved to live on over billions of years.

[1] https://en.m.wikipedia.org/wiki/Human_extinction

[2] https://www.jpl.nasa.gov/edu/news/2022/9/22/the-science-behi...

Without humans. Redundancy is important.

True, but irrelevant to the point that it's a different basket.

It's not irrelevant. Virtually the only conceivable thing that could make Earth even temporarily as inhospitable to humans as Mars is today is an impact close to the one that created the Moon. For any other scenario, some places on Earth will continue to be more inhabitable to humans even during the event itself than Mars is today.

So, having humans on Earth + Mars at best only marginally improved the chances of humanity surviving long term than only having humans on Earth, by a tiny amount.

the "eggs in one basket" argument only makes sense if Martian colonization is itself just step 1 on a list of dozens of similarly-difficult leaps to get us to terraforming and interstellar colonization.

It's a very exciting, multi-generational project to think about. Though frankly I think we're going to get AGI + brain/computer interfaces + cloud mind uploads before we get martian terraforming; and dropping the bag-of-meat related requirements would make extraterrestrial colonization much easier.

I think we will do both - and everything in between! Even just because you can never get all people top agree on something. :)

That's also the best option, not betting on a single idea or technology.

Depends on what would kill everyone on earth. More importantly, if everyone on earth dies having a 100,000 people living on Mars isn’t enough they also all die.

If they're self-sufficient, they could survive. Human population on Earth has bottlenecked to less than 100,000 in the past and we recovered.

Are we sure that getting to 100,000 self-sufficient humans on Mars will take less time than getting to 100,000 self-sufficient humans on the Moon? The conditions on the Moon are harsher, but our ability to move people and supplies there seems much greater. And what exactly is the extinction event that would threaten both Earth and a self-sufficient Moon colony?

Self-sufficient seems like quite the bar though. I guess they wouldn't need fancy electronics etc, but I imagine they'd still need non-trivial metallurgy, chemistry and similar in order to survive.

That is, they can bring a lot of fancy stuff with them, but to be self-sufficient they'd have to be able to maintain, repair and ideally rebuild what they need indefinitely without resupplies from Earth.

If we ever get to the point where thousands of people are moving to Mars, thousands will also be moving to the Moon, and vice versa. I don't see it as being just one or the other because the problems that need to be solved are approximately the same, and the cost of shuttling people and supplies is far from the hardest.

Getting to the moon or mars is trivial compared to stable self sufficiency.

I’d say 100k self-sufficient humans isn’t enough to support postindustrial civilization even on Earth without a hazardous scenario. Imagine aliens extracting all cities and all signs of technology except one town and dropping off some automated libraries, datacenters, labs, factories and other important equipment in a working condition around there. These 100k people wouldn’t be able to maintain it and pass it down the next generation. On anything non-Earth they would go extinct in one lifetime.

this is a pretty fascinating question. Yes, they definitely wouldn't be able to create say Intel fabs, since the "market" cannot sustain it. But, being a very adaptable species, could they gracefully scale down the tech to keep making what's needed for survival? It's similar to time travel, if you got dropped into the middle ages, would your knowledge be useful to them? here it's like the reverse: having seen everything in an advanced civilization, can a resource-constrained team pick out and keep the most important core?

Not for long I guess. Maintaining advanced hardware is hard because it sits on top of a technological pyramid, and the next layer is also advanced hardware, which sits on top of a… you get the idea.

I think that it could be possible for them to focus on few important/key paths, in theory. But, unless they research and prepare for exactly that scenario and chances that it works would be strictly in their favor and they all would work hard, learn hard and motivate themselves through their entire life, I don’t see how it could work. Not to mention political, social, religious risks with the next generation.

I’m not 100% sure ofc, that would be no doubt an interesting “experiment”.

Being self sufficient isn’t nearly enough on it’s own to ensure survival.

I think 100,000 people on Mars also kinda implies a substantial space infrastructure to support them & possibly a sizeable population elsewhere.

All the space infra could also possibly help detecting and averting space born threats, such as asteroids on a collision course.