Paraterraforming vs. terraforming the Moon and Mars

William wrote:

> > What about radiation shielding?
>
> We have sunglasses now that are UV resistant. I think it's not that
> big of a jump to have dome surfaces that are too. Solar flares and
> cosmic rays, now that might be a problem, and might be a technical
> hurdle that would have to be overcome.

Yes, it was those I was thinking of, not UV. There are only two ways
known to stop cosmic radiation: shielding mass equivalent to a couple
meters of dirt, or magnetic fields. The latter might be possible for a
domed city someday, but it's certainly nontrivial.

> > Real gravity, but perhaps not enough of it.
>
> I was talking about tourism, not permanent settlement.

Gotcha. I agree that for tourism, Martian gravity is plenty (and
probably good fun).

Best,
- Joe