Quite a crash in their fortunes, as Zo reminded the young man without much subtlety. Which meant they needed to cooperate with their more conveniently located allies in the system. “Otherwise the risk of Terran return to dominance is very real.”

“Terra is too enmeshed in its own problems to endanger anyone else,” the young man said.

Zo shook her head gently. “The more trouble Terra is in, the worse danger for the rest of us. That’s why we’re worried. That’s why we’re thinking that, if you don’t want to enter into an agreement with us, we may just have to build another city and track system on Mercury, down in the southern hemisphere, and cruise in the terminator down there. Where some of the best metal deposits are.”

The young man was shocked. “You couldn’t do that without our permission.”

“Couldn’t we?”

“No city on Mercury can exist if we don’t want it to.”

“Why, what will you do?”

The young man was silent.

Zo said, “Anyone can do what they want, eh? This is true for everyone ever born.”

The young man thought it over. “There’s not enough water.”

“No.” Mercury’s water supply consisted in its entirety of small ice fields lying inside craters at the two poles, where they remained in permanent shadow. These crater glaciers contained enough water for Terminator’s purposes, but not much more. “A few comets directed at the poles would add more, however.”

“Unless their impact blasted all the water on the poles away! No, that wouldn’t work! The ice in those polar craters is only a tiny fraction of the water from billions of years of comets, hitting all over the planet. Most of the water was lost to space on impact, or burned off. The same thing would happen if comets struck up there now. You’d get a net loss.”

“The AI modelers suggest all kinds of possibilities. We could always try it and see.”

The young man stepped back, affronted. And rightly so; you couldn’t put a threat much more explicitly than that. But in slave moralities the good and the stupid tended to become much the same, so one had to be explicit. Zo held her expression steady, though the young man’s indignation had a commedia dell’arte quality that was quite funny. She stepped closer to him, emphasizing their difference in height; she had half a meter on him.

“I’ll give the Lion your message,” he said through his teeth.

“Thanks,” Zo said, and leaned down to kiss him on the cheek.