This is one of the biggest points people miss when talking about civilization back ups. I tend to think of it in IT terms: the moon is like an offline but onsite backup. It will protect you from most internal cockups where as Mars is more like an offsite backup which will protect you should your building (Earth) get taken out

Meteor impacts and supervolcanoes seem to be the near-term worst case scenarios, neither which change the state of living on the moon. I don't know that the metaphor of them being under the same roof works.

I know the risks are astronomical (literally), but anything significant enough to alter Earth's mass would also alter the moons orbit.

I just think if we are talking about an extraterrestrial base for the sake of "backing up" the human race then it is prudent to pick a location that isn't in any way dependant on the master copy.

However I appreciate other concerns also take priority as well (cost, practicality, etc) but if the topic were strictly just about backing up humanity then my ideal candidates would be Mars plus some location outside of our solar system. But I'm venturing well into the realm of sci-fi now.

What's the point of a backup though if you can't restore?

I'm not sure I understand your point. Are you implying we shouldn't be backing up the human race because "what's the point if Earth is destroyed?"

If there's humans, the possibility to restore exists.

If there's no humans, the possibility to restore is gone.

It's not necessarily a either or situation. I can certainly see this work out in a way where you can iterate quickly on the moon resulting in technologies maturing quickly that you will eventually need on Mars and ultimately get you there faster than trying to go straight to Mars.

I'm having trouble thinking of catastrophes that could take out both. Well, I can think of a few (bio-weapon, nearby supernova) but they would take out a Mars colony just as easily.

I think they meant that if we have civilisation collapse on Earth then the Lunar folk are screwed too, because their supplies would be cut off permanently.

Why would the Moon be any less independent than Mars? It is only 20% less delta-V to ship something there. It is just as much in their interests to become self-sufficient.

Depends how much supply they have. A mature lunar colony should have a stockpile and equipment sufficient for reconstructing any equipment needed.

At that point, asteroid mining may be cheaper than launching resources from earth.