Solar flares present a huge problem for people living on Mars unless they’re underground. They destroy any technology that isn’t well-shielded. They also represent a major obstacle to a project to terraform Mars because the charged particles will strip away the atmosphere you’re trying to build.
> They also represent a major obstacle to a project to terraform Mars because the charged particles will strip away the atmosphere you’re trying to build.
Not at a rate fast enough to matter, it's negligible on human timescales.
I'm totally down for how nifty it would be to have off-world colonies, but trying to sell it to the public with these "what if" arguments doesn't even begin to pass the sniff test. Gates has been sounding the alarm for years about viral pandemics and basically nothing was prepared for it; how capable would we be of spending trillions on a "backup Earth" when we can't even spend a few million a year on stockpiling medical PPE?
Barring a general change in the habitability of the Moon/Mars or other astronomical body I'd wager that you would have a similar dynamic. If unique economic purposes are discovered including rich surface deposits, low-G fuel generation, or lower environmental concerns then the population in these settlements would grow for the same reasons that people have always moved to the frontier.
Once the transit economics are understood, The Moon and Mars can both provide accessible surface deposits of water, iron, copper, and other commodities to orbit for less energy than earth. A number of activities for resource procurement for commercial space industries will be a tad easier when attached to a big low-g rock where an extra green house can simply be dug out. The relative lack of environmental externalities from mining and other activities may be a resource unto itself in the next few decades.
On a longer timeline - Mars could be given a tolerable atmospheric pressure and liquid water for <100 trillion dollars. Barring a change in global growth rates that would be ~3% of annual global GDP by 2120, and .1% by 2220.
https://www.nasa.gov/press-release/nasa-mission-reveals-spee...
I don't think you need solar wind-magnitude energies for Venus to have lost it's hydrogen, it just sped up the process. Venus is pretty big, but it's also really hot. Venus' gravity to temperature ratio permit significant amounts of free hydrogen to be lost thermally without any solar wind sweeping it away. I think it's possible that Venus lost most of its hydrogen to thermal escape, particularly hydrodynamic escape, though today it's no longer the predominate mechanism for what little hydrogen remains.
The Wikipedia article (https://en.wikipedia.org/wiki/Hydrodynamic_escape) on hydrodynamic escape talks about escaping heavy molecules as if that's the principle function of the mechanism. But in much of the scientific literature on early Venus, hydrodynamic escape seems to refer primarily to the escape of free hydrogen.[1] I'm not a scientist so I don't know what to make of that, but in any event thermal mechanisms (i.e. Jeans and hydrodynamic) can absolutely cause gaseous particles to reach escape velocity.
[1] Photodissociation splits H2O, hydrogen is kicked out into space via thermal mechanisms, and much of the remaining oxygen, too heavy to escape at a significant rate under the local parameters, is sequestered by the molten core, volcanism, and surface weathering. At least, that's how I understand the literature as a layman. The modern debates and research seem to be centered around the particularities, especially the early geology, such as how long core material was exposed.
Also - why is this a response to the person you responded to?
It's the latter that a large scale catastrophe on earth causes.
It has no earthquakes, no volcanoes, no hurricanes, no tornadoes, no floods, no forest fires, and so on. It has exactly two types of natural disasters - meteor strikes, and dust storms. The former are very rare. The latter can be mitigated much more thoroughly than natural disasters on earth.
Humans have to live indoors, which mean that it has no shared ecosystem. We can control the spread of pathogens by isolating populations perfectly. We don't have to worry about the atmosphere at large becoming poisonous because we are already managing the local atmosphere as a distinct entity.
It has no large groups of people who do not have the technology to survive in hostile environments who can come try and steal (and in effect destroy) your technology.