Sorry, I can't let this go unchallenged.

The "news" reports on net-gain fusion all the time.

https://www.sciencenews.org/article/nuclear-fusion-breakthrough-energy

https://www.cnn.com/us/live-news/nuclear-fusion-reaction-us-announcement-12-13-22/index.html

https://www.bbc.com/news/science-environment-60312633

https://www.forbes.com/sites/qai/2022/12/14/nuclear-fusion-breakthrough-the-future-of-clean-limitless-energy/

https://www.cbsnews.com/news/nuclear-fusion-60-minutes-2023-01-15/

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What they don't report is that it's a false measure based on the energy of ignition while ignoring the energy of containment. Here's the best video I know of to explain it.

https://www.youtube.com/watch?v=LJ4W1g-6JiY

I agree 100%. Callisto gets less radiation than the Earth does.

Robotic craft could also mine the other Jovian moons for raw materials, possibly including hydrocarbons.

It's an excellent vantage point for deep-space observations and close-up study of Jupiter and its other moons. The only real challenge is energy. Solar is way too weak out there.

You should read Ender's Game by Orson Scott Card.

I can't tell you why. Spoilers.

But it has something to do with "down", in space...

Yes, it is possible. It's highly unlikely that they'd be the same, like most women's boobs. One is always a little bigger than the other.

Here's the thing that no one else here has mentioned -- The orbits of two similarly sized objects around each other (such as Venus and Earth), while also being in orbit around a much larger object (the sun) is much more stable if the planet's orbits around each other is in the opposite direction as their orbit around the sun. (clockwise and counter-clockwise, for example.)

That's how the math works, but weirdly, there are no examples of counter-rotating natural satellites in our solar system, even though they should be more common.

There is still much we do not understand in the universe.