Lvov, five light hours from home, found it difficult to respond to the mail asynchronously. She felt as if she had been cut out of the online mind of humanity. In the end she drafted replies to her family, and deleted the rest of the messages.

She checked her research equipment again, but it really was unusable. She tried to sleep. The suit was uncomfortable, claustrophobic. She was restless, bored, a little scared.

She began a systematic survey of the surface, taking her scooter on widening spiral sweeps around the crash scar.

The landscape was surprisingly complex, a starlit sculpture of feathery ridges and fine ravines. She kept a few hundred feet above the surface; whenever she flew too low her heat evoked billowing vapor from fragile nitrogen-ice, obliterating ancient features, and she experienced obscure guilt.

She found more of the snowflakelike features, generally in little clusters of eight or ten.

Pluto, like its moon-twin Charon, was a ball of rock clad by thick mantles of water-ice and nitrogen-ice and laced with methane, ammonia and organic compounds. It was like a big, stable comet nucleus; it barely deserved the status of “planet.” There were moons bigger than Pluto.

There had been only a handful of visitors in the fifty years since the building of the Poole wormhole. None of them had troubled to walk the surfaces of Pluto or Charon. The wormhole, Lvov realized, hadn’t been built as a commercial proposition, but as a sort of stunt: the link which connected, at last, all of the System’s planets to the rapid-transit hub at Jupiter.

She tired of her plodding survey. She made sure she could locate the crash scar, lifted the scooter to a mile above the surface, and flew towards the south polar cap.

Cobh called from the Interface. “I think I’m figuring out what happened here — that superluminal effect I talked about. Lvov, have you heard of an Alcubierre wave?” She dumped images to Lvov’s desk — portraits of the wormhole Interface, various graphics.

“No.” Lvov ignored the input and concentrated on flying the scooter. “Cobh, why should a wormhole become unstable? Hundreds of wormhole rapid transits are made every day, all across the System.”

“A wormhole is a flaw in space. It’s inherently unstable anyway. The throat and mouths are kept open by active feedback loops involving threads of exotic matter. That’s matter with a negative energy density, a sort of antigravity which—”

“But this wormhole went wrong.”

“Maybe the tuning wasn’t perfect. The presence of the flitter’s mass in the throat was enough to send the wormhole over the edge. If the wormhole had been more heavily used, the instability might have been detected earlier, and fixed…”

Over the gray-white pole, Lvov flew through banks of aerosol mist; Cobh’s voice whispered to her, remote, without meaning.

Sunrise on Pluto:

Sol was a point of light, low on Lvov’s unfolding horizon, wreathed in the complex strata of a cirrus cloud. The Sun was a thousand times fainter than from Earth, but brighter than any planet in Earth’s sky.

The inner System was a puddle of light around Sol, an oblique disc small enough for Lvov to cover with the palm of her hand. It was a disc that contained almost all of man’s hundreds of billions. Sol brought no heat to her raised hand, but she saw faint shadows, cast by the Sun on her face plate.

The nitrogen atmosphere was dynamic. At perihelion — the closest approach to Sol, which Pluto was nearing — the air expanded, to three planetary diameters. Methane and other volatiles joined the thickening air, sublimating from the planet’s surface. Then, when Pluto turned away from Sol and sailed into its two-hundred-year winter, the air snowed down.

Lvov wished she had her atmospheric-analysis equipment now; she felt its lack like an ache.

She passed over spectacular features: Buie Crater, Tombaugh Plateau, the Lowell Range. She recorded them all, walked on them.

After a while her world, of Earth and information and work, seemed remote, a glittering abstraction. Pluto was like a complex, blind fish, drifting around its two-century orbit, gradually interfacing with her. Changing her, she suspected.

Ten hours after leaving the crash scar, Lvov arrived at the sub-Charon point, called Christy. She kept the scooter hovering, puffs of gas holding her against Pluto’s gentle gravity.

Sol was halfway up the sky, a diamond of light. Charon hung directly over Lvov’s head, a misty blue disc, six times the size of Luna as seen from Earth. Half the moon’s lit hemisphere was turned away from Lvov, towards Sol.

Like Luna, Charon was tidally locked to its parent, and kept the same face to Pluto as it orbited. But, unlike Earth, Pluto was also locked to its twin. Every six days the worlds turned about each other, facing each other constantly, like two waltzers. Pluto-Charon was the only significant system in which both partners were tidally locked.

Charon’s surface looked pocked. Lvov had her face plate enhance the image. Many of the gouges were deep and quite regular.

She remarked on this to Cobh, at the Interface.

“The Poole people mostly used Charon material for the building of the wormhole,” Cobh said. “Charon is just rock and water-ice. It’s easier to get to water-ice, in particular. Charon doesn’t have the inconvenience of an atmosphere, or an overlay of nitrogen-ice over the water. And the gravity’s shallower.”

The wormhole builders had flown out here in a huge, unreliable GUTship. They had lifted ice and rock off Charon, and used it to construct tetrahedra of exotic matter. The tetrahedra had served as Interfaces, the termini of a wormhole. One interface had been left in orbit around Pluto, and the other had been hauled laboriously back to Jupiter by the GUTship, itself replenished with Charon-ice reaction mass.

By such crude means, Michael Poole and his people had opened up the Solar System.

“They made Lethe’s own mess of Charon,” Lvov said.

She could almost see Cobh’s characteristic shrug. So what?

Pluto’s surface was geologically complex, here at this point of maximal tidal stress. She flew over ravines and ridges; in places, it looked as if the land had been smashed up with an immense hammer, cracked and fractured. She imagined there was a greater mix, here, of interior material with the surface ice.

In many places she saw gatherings of the peculiar snowflakes she had noticed before. Perhaps they were some form of frosting effect, she wondered. She descended, thinking vaguely of collecting samples.

She killed the scooter’s jets some yards above the surface, and let the little craft fall under Pluto’s gentle gravity. She hit the ice with a soft collision, but without heat-damaging the surface features much beyond a few feet.

She stepped off the scooter. The ice crunched, and she felt layers compress under her, but the fractured surface supported her weight. She looked up towards Charon. The crimson moon was immense, round, heavy.

She caught a glimmer of light, an arc, directly above her.

It was gone immediately. She closed her eyes and tried to recapture it. A line, slowly curving, like a thread. A web. Suspended between Pluto and Charon.

She looked again, with her face plate set to optimal enhancement. She couldn’t recapture the vision.

She didn’t say anything to Cobh.

“I was right, by the way,” Cobh was saying.

“What?” Lvov tried to focus.

“The wormhole instability, when we crashed. It did cause an Alcubierre wave.”

“What’s an Alcubierre wave?”

“The Interface’s negative energy region expanded from the tetrahedron, just for a moment. The negative energy distorted a chunk of space time. The chunk containing the flitter, and us.”