Sure, Humans going to Mars and back would be cool. Attempting to establish any permanent presence there let a lone a colony with more than a dozen or so people there would be an inconceivable massive waste of resources.

Something that nobody should be allowed to even try to do in the foreseeable future even id that person managed to get enough resources for that.

In your opinion what would it take to make it worthwhile?

Eg. If you scale out to a 10,000 year timeframe and this is step 1 leading to a self-sufficient backup for Earth, then one day some event seriously threatened to take out our home planet, suddenly the ~whole population would feel the expense was worth it whatever the magnitude.

I don’t really feel capable of giving a reasonable answer to that question. The ability to terraform it?

> If you scale out to a 10,000 year timeframe

AFAIK there were no events at last several hundred million years that had a realistic chance of making the Earth less habitable that Mars. So unless we had a ways to cheaply transport millions of people to Mars (maybe space station or the moon would be a better option though?) focusing on building infrastructure that would allow us to minimize the impact of meteorites or massive volcanic eruptions as much as possible.