Io, the innermost of the Galileans, was more difficult, but intriguing; rail-gun launchers were firing large missiles of ice and chaldates down to it from the other three big moons; being so close to Jupiter it had very little water, its surface made up of intermixed layers of basalt and sulfur— the sulfur spewing out onto the surface in spectacular volcanic plumes, driven by the tidal action from Jupiter and the other Galileans. The plan for Io’s terraformation was more long-term than most, and was to be driven in part by an infusion of sulfur-eating bacteria into hot sulfur springs around the volcanoes.

All four of these projects were slowed by the lack of light, and space mirrors of tremendous size were being built at Jupiter’s Lagrange points, where the complications of the Jovian system’s gravitational fields were reduced; sunlight would be directed from these mirrors to the equators of the four Galileans. All four moons were tidally locked around Jupiter, so their solar days depended on the length of their orbits around Jupiter, ranging from forty-two hours for Io to fifteen days for Callisto; and whatever the length of their days, they all received during them only four percent as much sunlight as the Earth. But the truth was that the amount of sunlight hitting the Earth was stupendously excessive, so that four percent was actually a lot of light, when it came to visibility— seventeen thousand times as much as the full moon on Earth— but not much heat, if one wanted to terraform. They therefore were cadging light any way they could; Lake Geneva and all the settlements on the other moons were located facing Jupiter, to take advantage of the sunlight reflected from that giant globe in the sky; and flying “gas lanterns” had been dropped into the upper atmosphere of Jupiter, clusters of them igniting some of the planet’s helium3 in points of light that were too brilliant to look directly at for more than a second; the fusion burns were suspended before electromagnetic reflecting dishes that put all the light out into the planet’s plane of the ecliptic. Thus the banded monster ball was now made an even more spectacular sight by the achingly bright diamond dots of some twenty gas lanterns wandering its face.