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Titan

Titan is larger than Pluto, larger than Mercury. It has a nitrogen atmosphere, like Earth’s but ten times more dense. Temperature at the surface is ninety K, but there is a liquid-water ocean deep under its surface that serves as a reservoir of potential warmth. On the surface all the water is frozen very hard and forms the material of the landscape—glacial to every horizon, with rock ejecta scattered here and there like warts and carbuncles. Here methane and ethane play the role of water on Earth, changing from a vapor in the nitrogen atmosphere to clouds that rain down into streams and lakes running over the water ice.

Sunlight hitting this atmosphere strikes up a yellow smog of complex organic molecules. The hydrogen in this haze escapes easily into space, but while in Titan’s air, it drives all the bigger organic molecules back to simpler building blocks; so there are not many complex organics, and therefore no indigenous life. Not even in the water ocean below, as if the corrosive atmosphere formed some kind of quarantine.

The glacial surface is broken in most places, smooth in a few. When you stand on the surface, you can see Saturn, with a thin slicing curve of the edge-on rings cutting the gas ball in half; you can also see the brighter stars. The haze in the Titanic air is of a thickness such that looking out of it, visibility is fairly good, while looking into it is to see nothing but a yellow cloud.

No impact craters; as they are formed in ice, the ice then deforms and resurfaces as the centuries pass. There is only a convoluted, swirling chaos of broken ice features and rock outcroppings, cut by liquid methane into shapes like watersheds. Dips in the land are filled with liquid methane: Titan’s Lake Ontario is three hundred kilometers across, and shaped like the one on Earth.

There is seasonal weather, as Saturn makes its way from perihelion to aphelion: methane rain in the rainy season.

It was the nitrogen that first brought people to Titan. Martians, unhappy with the never-explained shortage of nitrogen on Mars, flew out in the first ships fast enough to be practical for human use over these distances; robots had preceded them, of course. They set up stations, built a system for gathering and freezing nitrogen and casting it downsystem in naked solid chunks. People complained this was an unauthorized expropriation, but the Martians pointed out that Titan in its distant past had had several times as thick an atmosphere as it had now, that the nitrogen was leaking away to space to no one’s advantage, that if it wasn’t harvested it would go away—and that there were no Titans. The last argument was decisive. By the time there were Titans, by the time Titan and the rest of the Saturn League had ejected the Martian nitrogen miners from their system, Titan’s atmosphere had been reduced by half. Mars was correspondingly enriched, with part of the imported nitrogen in its soil, part in the atmosphere; it formed a crucial component of the Martian Miracle. And the Martians claimed no harm had been done; that in fact it had helped Titan’s future prospects, by getting it closer to a human-friendly pressure.

The loss of Dione in those same years, however, was not a loss that could be claimed to help Saturnians in any way. The Saturn League then declared their system off-limits to Martians, also to Terrans (the Chinese in particular)—to anyone, in fact, except themselves. It was the first post-Martian revolution, against the great revolutionaries themselves, a statement very forcefully made by the threat of bombardment. So everything changed once again, because of a few people on Titan.

The new light from the Vulcanoids sparking now in the skies of Titan had already started temperatures in the remaining atmosphere to rise, and the surface was therefore subliming faster than before. The tented cities in the highlands now had some of the most violent weather anywhere. From the inside of the city tents, the Titans watched clouds rising in thunderheads that sheered off horizontally some five kilometers up, where jet streams decapitated them. Sunlight before had been one one-hundredth of that striking Earth, making the whole planet seem about as bright as an ordinary room; now, with its beamed and reflected additions, it was fifty times brighter than it had been naturally, and was said to resemble the light on Mars, which the Martians said was the best light of all. In truth the human eye could adjust to a huge range of incoming light, and very little would serve for seeing, as had been the case here before the mirrorlight arrived. Now however the Titanic landscape positively glowed, and as its orbit and day were both sixteen days long, the sunsets, when they tinted the clouds to every shade of mineral glory, burnished the sky for some eighteen hours at a time.

With the new influx of light, the full terraformation of Titan seemed very promising. They could capture and export the methane and ethane; spread foamed rock to make islands on the ice; use heat from the ocean below to warm the atmosphere; melt water lakes on their islands of rock and soil; landscape the islands, introduce bacteria, plants, animals; heat the air enough to get melted seas on the glacier surfaces; hold the atmosphere inside an ultrathin bubble; and light everything with the sunlight sent up from the Vulcanoids. The Titans looked out their tent walls with sharp anticipation. My oh my, they said. If we can just keep our shit together here we’re gonna make this a real nice place.