“It doesn’t look like a disaster,” Drake added. He and Ana were strolling along the shore, bareheaded.

She paused and skipped a flat stone over the brackish waters of the estuary. “Believe me, it was.”

“What caused it?”

“The usual: stupidity. We still have our share of that. The old assumption was that Earth’s whole biosphere had strong homeostasis. Disturb it, no matter how, and forces would come into play to restore it to its original condition. So while everyone was looking the other way, not worrying about this planet and wondering what to do with Venus and Europa and Ganymede and Titan, Earth started an environmental runaway.”

“Runaway how?”

“Temperature, mostly. The atmospheric composition was starting to change, too, but the biggest problem was greenhouse warming. It was caught before it could go too far. Turning it around was another matter. For a while, people were imagining a new homeostatic end point, with temperatures hot enough to boil water.”

Drake stared out over the peaceful estuary. “Hubris,” he said, in English.

“What?”

“Too much arrogance; the belief that you can do anything.”

Ana stared at him. “Anything, no,” she said at last. “A lot, yes. Recovery has been slow but steady. Mean equatorial temperatures are below forty degrees Celsius. The land animals are heading out of the temperate zone jungles, and they’re traveling sunward. Don’t worry, we’ve learned our lesson. This won’t happen again — ever.”

“I’ve learned not to trust ever.” Drake looked north. “We used to live in a place called Spring Valley. If I tell you how to reach it, could we go there?”

“Were you living up in the mountains, or close to sea level?”

“Down right at the shore.” Drake did not notice the change Ana had made, from “we” to “you.”

“Then we could go there, but it would be a waste of time. I don’t just mean the heat — suits would take care of that. But sea levels are up. Your old home will be under five to ten meters of water. Come back again in ten thousand years. The sea level should have dropped enough for you to pay a visit on dry land. But if you’d like to visit mountains, I have my favorites.”

“You’ve been to Earth before?” It seemed like a ludicrous question — his Ana had been born and raised on Earth.

But she just nodded. “Five times. It’s a backwater, but it’s on every tourist list. The original home, the birthplace, the shrine of humanity. But if most people were honest, they’d admit that it’s rather dull. It’s not where the action is. Are there other things that you want to see?”

“My old mentor, Par Leon, lived deep beneath the African plateau. That was high above sea level. I know the location. If we could just fly over there …”

“Of course.”

Ana agreed readily, although she must have suspected what they would find. Africa, at ten degrees north of the equator, was a seared world of dust and dead rock. The snows of Birhan were a memory, the peak a stark blackness jutting into a sky of fuming yellow. Drake looked at it and nodded to Ana. He had seen enough.

They took off for space and wandered to the innermost system. Venus terraforming, according to Ana, was right on schedule. The surface pressure was down from a stupefying ninety Earth atmospheres to less than twenty. Bespoke bacteria converted the sulfuric acid clouds to sulfur, water, and oxygen. The sulfur was delivered to the deep planetary interior. It would not emerge for hundreds of millions of years. Cyanobacteria, seeded into the upper atmosphere, went about their steady business, absorbing carbon dioxide, releasing oxygen, fixing nitrogen, and delivering a rain of organic detritus to start a planetary topsoil.

“Water is still the main problem,” Ana said. “There’s simply not as much as we would like. Venus will always be dry, unless we do an extensive Oort Cloud transfer, or combine the planet with one of the big Jovian water moons, like Callisto.”

“Is that feasible?” The cure for temporal shock seemed to be working; Drake was starting to feel that anything was possible. But flying a satellite of Jupiter to coalesce with an inner planet? That still sounded ludicrous.

“It’s not feasible yet,” Ana said. “The impact would destroy Venus. But we’re learning how to do a soft merge. For the moment, I don’t recommend we make a Venus landing. It’s too hot down there — hotter than Earth ever got, even at the height of the runaway. It would have to be suits all the time. Are you ready to go somewhere else?”

Drake nodded.

“Right.” Ana paused at the control panel. “Lots of options. Unless you’re really keen, I suggest that we skip Mercury completely. It has the research domes, but nothing really worth seeing.”

The ship flew on, skimming the broad face of the Sun. Close up, that mottled surface was as raging and demonic as anything that Drake had encountered on his visit to Canopus. They passed through hydrogen prominences that roared and flamed with prodigal energy. Drake remained unperturbed. The ship’s refrigeration held the interior temperature at a comfortable level; in any case, Ana was at his side.

The Sun fell rapidly behind, and the outward journey began. Drake did not care where he went. It was at Ana’s insistence that they head for Mars.

“Just for fun,” she said.

It did not sound like fun. Drake recalled the fury of the Mars bombardment, the cloud-streaked sky of dirty gray and the torn and quaking surface.

But…

Twenty-nine and a half millennia was a long time. Drake’s memories were distant history. Their landing was in midmorning, on a calm world of thin, clear air and dark blue sky.

“A lot more atmosphere than there used to be,” Ana said, as Drake gazed out at a green cover of plants, a thin carpet from which jutted hair-thin stems with fat blue lollipops at their ends. “But there’s not nearly enough oxygen to breathe. Not for us, at least.”

“Why did they stop halfway?” Drake was becoming blasй when it came to planetary transformation. “I’d have thought Mars would be easy.”

“It would. You’ll see why in a minute.” Ana watched as Drake disappeared within his bulky symbiote. She tried to restrain herself, then began to giggle helplessly.

“I’m sorry. I know I’m going to be the same — but just look at you.”

Drake did. In a mirror he saw a mournful marsupial, an overweight kangaroo with a wobbling paunch and a long camel’s nose. The outsized ears stuck up to provide a constantly surprised expression. He stuck out his tongue. The face in the mirror extended a black appendage at least a foot long. He blinked. The dark liquid eyes blinked back at him, protected by an inner transparent membrane and outer lids with eyelashes long and thick enough to be the envy of any glamour queen.

Ana was allowing her own symbiote to envelop her. “Now we can go out,” she said, as her new body seemed to inflate before Drake’s eyes. “Follow me.”

To hell, if you ask me to. But he had already done that. Drake heard the hiss as the ship’s cabin pressure dropped. The hatch opened. He did nothing, but his great paunch began to move in and out with its own rhythm. He saw that Ana’s belly was doing the same.

“If you decided to live here,” she said, in a voice half an octave higher than usual, “you wouldn’t have to make a decision whether to live on the surface, where there’s not much oxygen, or in the deep caverns, where there is. You’d just let your symbsuit sort that out, and provide whatever you need. Mars surface dwellers never disengage from their symbsuits. They eat, drink, sleep, and die with them — even when they go to the caverns.”

Drake could understand why, when they left the ship and began to wander the broken plain outside. It didn’t feel anything like wearing a suit. The symbiote was his own body. It merely happened to be a new body that could endure extreme cold and make do on less than a quarter of a human’s oxygen needs.