She was on the Pleistocene. She carried a stun gun.

But she had left it in the nest. “Shit.”

The cat began to shift onto Swan’s branch. Quite a weight to sway it that much.

“Pauline, any suggestions here?”

“Scare it,” Pauline said. “Adrenalate fully, then do something bizarre.”

Swan twisted and let go, fell feetfirst into the face of the cat, screaming as loud as she could. When her feet hit something else, she clasped branches to her and felt something smash into her ribs. Air knocked out of her, no more scream. She scrabbled with her feet for some purchase, found none, looked down. The cat was on the ground, looking up at her. Swan screamed again, felt the stab of a cracked rib. She changed to a raging shout, cursing the cat foully. Kill it like Archilochus. Grating, painful snarl of a voice, bitter shrieking that hurt her throat and screeched unbearably in her own ears, the sound making her aware she had lost it. The cat heaved a heavy sigh and padded away.

She climbed back to her nest and retrieved the stun gun. Getting down out of the tree hurt like hell.

She avoided Wahram completely after that, and by the time they were dropped off on Callisto, she had become a little fond of that stab in her side. It made her feel better; it was an expression of her grief, her anger. The moment of dread involved was not forgotten, but digested into something else, some kind of triumph. She had almost been eaten for breakfast! She had been a fool and survived yet again—how often it had happened. Surely it was a fate. Surely it would keep on happening.

“This is the most basic of false syllogisms,” Pauline assured her when she spoke the thoughts aloud.

The Jovian moons were huge, with Jupiter itself a gargantuan oil painting of overelaborate genius, viscous blobs swirling around from one gorgeous paisley orangerie to the next; every border between the bands was a fantasia beyond compare. Swan loved the sight of it, and the city from which she viewed it wasn’t bad either: the Fourth Ring of Valhalla, built on the eponymous rim of the great multi-ringed crater. Valhalla had six rings, splashed into the side of Callisto like concentric waves on a pond after a rock is thrown in. The city was located on the top of the fourth ring, extending all the way around; now cities were beginning on the tops of the third and fifth rings as well. It was said that they would eventually tent the entirety of Valhalla and, after that, maybe all the rest of Callisto; and it was a big world. There were even those arguing it could be properly terraformed, despite the lack of a starter atmosphere.

It was one big world of four, in fact, because all the Galilean moons were gigantic. But there was some kind of a curse on them, it seemed to Swan; one of them was almost useless, another contested. Io orbited so far within Jupiter’s ferocious radiation belts that it was never going to be occupied at all except by a few small hardened scientific stations. Europa, a big beautiful ice moon, had a great depth of ice for people to delve into to escape the Jovian radiation, strong even there: wondrous ice palaces, with giant Jupiter always gnarling overhead—or everyone had thought at first. But it hadn’t happened, because there had proved to be aliens living in the ocean below, a complete ecology of algae, chemotrophs, lithotrophs, methanogens, scrapers, suckers, fans, scavengers, and detrivores, all swimming or crawling or holding on or burrowing in; and they created a problem. Some thought they had already contaminated this ocean by their exploratory intrusion into it, because examining it with a drill had been the Lake Vostok problem writ large. But they had done their best to sterilize the probes, and then, having discovered and sampled the full ecology, they had sealed off the hole, and now sat on the surface in scientific stations, culturing and studying their sample populations and pondering whether they should stay or go, and if they stayed, what kind of presence they should have. Possibly the proposed ice palaces would be perfectly fine, with the life below completely sequestered by the ten kilometers of glaciosphere that lay between the moon’s surface and its ocean. On the other hand, life being life, spermatozoically wriggling into every place it could reach, contamination might almost certainly be assumed to follow any occupation of the moon. And yet, given that these creatures appeared to be cousins of theirs anyway, long separated by meteor voyage—and now already recontaminated by a visit—would living above them and continuing to be a minor contaminant clearly be such a bad thing? When there were already people out there swallowing the alien microscopic life, and shooting it into their veins? And when life had been bouncing around the solar system and interacting with its cousins all along? These were open questions, interesting and vivid to the Europans and the other Jovians, less so to the rest of the system. Swan remained somewhat interested from her design days, and she approved their recent decision to go ahead and settle Europa, only perching unobtrusively on top of the internal indigenous aquaria.

Now she spent her time walking the High Road that ran all the way round the Fourth Circle of Valhalla, waiting for their flight to Io. She was still avoiding Wahram, who watched her these days with a look of alarmed concern that she could not stand. Jupiter overhead was its usual lurid magnificence. Possibly the Jovians were right to be so self-absorbed; they had a whole little solar system here, full of different things. Between the rings of the crater, the surface of Callisto was a vast knobbly white plain, and Jupiter and the three other moons were up there performing their dance. It was a gorgeous space.

But they were here to see Wang, so soon she grew impatient for the Io shuttle, and tired of the view overhead. Jove squiggling its buffooneries over and over—it was not art but chemistry, mere fractal repetition. The saving grace was that they had recently lit great gas lamps in the upper Jovian atmosphere, to better illuminate the towns located on the Galileans’ Jovian sides. One could see how these painfully brilliant diamond points were distorting Jupiter’s cloud tops, adding new swirls and eddies; that made it art, the whole thing a kind of mad goldsworthy.

Finally the time came for the shuttle to Io.

Swan said, “Pauline, are you going to be all right down there?”

“I will be if you are. You definitely need to stay inside the Faraday cage there to stay safe. The Jovians will no doubt tell you that.”

And during the trip they did, at great length. In a box inside a box, like Russian dolls: they were so proud. Down then to Io, shedding a furious aurora behind their spacecraft, a blaze of transparent blue and green electric banners and flares arcing away as they flew.

IO

Io, the innermost moon of Jupiter, as big as Luna. The yellow slag world, awesome upchucking of a moon’s guts, regurgitation over and over until everything more volatile than sulfur has long since burned off. Sulfur, sulfur everywhere, and nary a place to stand. Four hundred live volcanoes bursting through the slag like angry boils, geysering sulfur dioxide hundreds of kilometers into the air. A moon with an interior hotter than Earth’s—and try putting your hand in front of the steam coming out of the volcanic vent on Néa Kaméni, in the caldera of Santorini, to feel just how hot Earth is; it looks like the steam on your stove top, but you will quickly find it is three times hotter. Even though you snatch your hand away instantly, your skin will blister. And Io’s interior is thirty times hotter than that.