“Leon.”

“Yes?”

“Oh, nothing. I’m just thinking about my trip.”

He stifled the idea before it could develop further. His new plans were shaping up, and they were nothing as simple as controlled freezing and a return to the cryowombs. They might lead to danger and destruction. He would not want Par Leon to bear any guilt by association.

He also would not — could not, dare not — do anything at all that might endanger his chances of success.

Drake had decided to proceed with great caution. For at least the first part of his trip, he must look and sound like a genuine tourist. His resurrection helped. He could tell anyone he met that he had been recently thawed (he would not define recently). He would say he was still trying to get the hang of his new era. He would gape at anything he saw, like the original hick. He would be free to ask a million innocent questions.

Drake had delved into solar system geometry long before he left Earth. At first he had been worried. By an accident of timing, Pluto was almost exactly at aphelion, as far away from the Sun as it could get. But then he looked at the performance of the ships. They could accelerate so hard, and achieve huge speeds so quickly, that nowhere in the system was more than a few days away. Travel times became irrelevant.

Mars, first, then, just as he had told Par Leon upon his departure. Drake could imagine his friend and mentor checking the first phase of his travel, but he would lose interest once he was sure that Drake had arrived safely.

Mars was described in the Earthside databases as undergoing a “modest” terraforming effort; nothing, the sources said, compared with the major effort going on at Venus. The Mars project was designed only to increase the available surface water, and it did not interfere with life in the Martian interior.

Drake’s ship took him to Mars in a day and a half. He landed; and found hell.

The planet was under ceaseless bombardment. Every twenty minutes a cometary fragment, a couple of hundred meters across, hit the surface. It had been directed in from the Kuiper Belt, nine billion kilometers from the Sun, and it struck Mars tangentially, precisely at dawn on the day-night terminator. Each impact came within twenty degrees of the equator. The Mars atmosphere was too thin to carry sound, but land waves shook the surface around the point of arrival.

Drake donned a suit and stepped out of the ship. He was well away from the impact zone. Even so, he felt the compacted rubble of the regolith tremble and shake beneath his boots.

He looked up. The sky was a dirty gray, streaked and filmed with white haze. Most of the added dust and water vapor in the air came not from comet fragments, but from the ejecta of vaporized surface rocks and permafrost, blown high into the Martian stratosphere. That permafrost was the main source of atmospheric water. It returned to the ground as a thin drizzle of ice particles. For the first time in a billion years, snow was falling on Mars.

As Drake watched, another ball of fire flamed across the dull southern sky. It moved from west to east, and vanished. One minute later a flash of crimson light lit the southeastern horizon. It was hard to believe that a rough-edged chunk of water ice, dirtied with smears of ammonia ice, silicate rock, and metallic ore, and no more than two hundred meters in diameter, could produce such violence. But a few million tons of mass, moving at forty kilometers a second, carries formidable amounts of kinetic energy. The energy release for each impact was around a thousand megatons. Each arrival had the force of a big volcanic explosion back on Earth. The thin atmosphere of Mars did little to dissipate it.

Drake watched the tumult for a couple of hours. Finally he decided that the open face of the planet, battered by hailstones bigger than the Great Pyramid, was more likely to stimulate nightmares than musical creation.

He went inside the ship and considered his next move. He had told Par Leon that he would visit the Mars deep caverns. Natural formations, kilometers across, they had been interlocked and fortified over the centuries by tunneling and construction moles. Now they stood second only to Earth as a center for human civilization.

Caution said he should visit the caves, as originally planned. After that, his original itinerary called for visits to Europa and Ganymede, the satellites of Jupiter, and to Neptune’s big moon, Triton. But a new knowledge was burning inside him. The trip to Mars had changed his perspective on interplanetary travel. He knew that he was, if he chose, only a few days away from Ana. From Mars to Pluto, even without invoking emergency status and maximum accelerations, was just a thirty-six-hour run.

The temptation was too much. He ordered a message sent to Par Leon, back on Earth, announcing his safe arrival on Mars. Then he gave his command.

The ship rose from the surface and arrowed out, directly away from the Sun’s warmth. It would bypass Jupiter and Saturn, bypass Uranus and Neptune. It would not stop until it reached Pluto, out at the frigid limit of the solar system; out where Sol was no more than a bright spark in the sky, and the cryocorpses slept their ancient, dreamless sleep beneath the silent stars.

A little knowledge could be almost too much. In six years of work on Earth, Drake had become used to the idea of robotic servants. They were of varying levels of intelligence, depending on their function, but they all had one thing in common: they accepted every command without question, provided that it was not dangerous and did not exceed their available resources of materials or knowledge.

He assumed that it would be equally true on Pluto, and it began that way. His ship landed without incident on the frozen surface. Machines attended his arrival. There were no humans, and he had expected none. The nearest people resided at the research station on Charon, seventeen thousand kilometers away. Pluto and Charon were more like a pair of little moons than a planet with a satellite — Pluto was smaller than Earth’s moon, while Charon was half the size of its primary. The pair were tidally locked, always showing the same face to each other. Drake, standing on the surface of Pluto and looking up, saw Charon hanging pendant in the sky above him, like a giant dull ruby. The research station was not visible. From this distance, there was no evidence to be seen on Charon of any human activities.

Even though Charon was so close, the machines on Pluto were designed to operate without advice or assistance from there or anywhere else. Drake’s command to be taken to the cryowombs was obeyed without question.

The surface of Pluto was one of the quietest places in the solar system. However, there would be occasional impacts from meteorites and cometary debris. The wombs, for additional safety, had been placed deep within the interior to protect against disturbance.

It had not occurred to Drake that he himself constituted such a disturbance, until he had been led at least a kilometer along a descending ramp. He and his attendant machine entered a large open chamber, where his suit was placed within another and larger one. The space between the suits was filled with liquid helium.

“Is this necessary?” He could imagine the second suit interfering with his mobility.

“It is necessary. There must be no energy release within the vaults to raise the ambient temperature. I myself cannot proceed beyond this point. I am too warm.” The machine raised a spidery articulated arm and pointed at a hovering blue pyramid, half a meter on a side. “This is now your guide.”

Ever since they left the surface it had become steadily darker. All light sources now disappeared as Drake followed the drifting blue pyramid out of the chamber and into the next level of the Pluto vault.