Hello, SFIA audio listeners.

In this month's Nebula exclusive, big alien theory,

we're asked at the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

Science fiction is popularized asteroid mining and cities in the sky, but could the future

of mining be in cloud cities hanging far above distant worlds?

As we get ready to finally start returning to the moon and contemplating mining it to get to the resources we need to settle the rest of the solar system, it is a good reminder

that very little of the actual resources in our solar system, and probably most others, is

inconveniently minable low gravity airless

moons and minor planets.

Off of Earth, in our own inner solar system, Venus makes up more mass than everything else

there combined, Mercury, Mars, All Moon, Mars Zone 2 Little Tiny Moons, and the millions of

asteroids in the belt, yet its surface is covered

with a terribly thick atmosphere whose contents are more like something coming out of a rocket

jet than what people inside that rocket could live and breathe.

Beyond the belt we have the gas giant Jupiter, which outmasses every other planet

in the solar system combined, and most of that remaining mass

is in its smaller sibling Saturn, which itself has the largest moon in the solar system,

Titan, with a thicker atmosphere than Earth's. Most of the remaining mass is in the two

ice giants, Uranus and Neptune. All these bodies are surrounded by thick atmospheres

which make getting material off

...