Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking 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.nebula.tv slash Isaac Arthur and use my code, Isaac Arthur.

In the future, we may be able to claim new worlds and forge them into paradises, but should we?

The survey ship Hydra and its pilot and captain, Brant and Jacobs, landed on HD18-445A's

third planet almost a month ahead of schedule,

and their first month there proved very exciting indeed.

It was a mineral-rich world with geology suggesting very stable solar output and geological cycles.

The planet gave every sign of being one of those planets surveyors dream of,

the kind with

everything colonists could want in terms of an easy target for tailforming. The day was even 24

hours and 12 minutes long. Their commission for surveying this planet was going to be huge,

because even a tiny percentage of a planet is still incomprehensible wealth. There was just one minor anomaly

in the area, where there were some lakes heavy on geysers and rich in phosphorus, way up in the

frozen tundra. When they got there, they realized why the rest of the planet was so dead. Life

if it had originated here couldn't have spread out to the icy plains beyond, but as they

went toward the shore of the nearest lake to take some samples, a mini-legged centipede-like

creature came out on the shore.

Brant and Jacobs stared at each other in chagrin through their helmets, then slowly,

deliberately, Jacobs crushed the alien critter under his boot.

It will have to go, Captain Jacob said.

...