It could be Cronos, he thought.

He wanted to try something.

The bubble was too small to allow him to stand up, but by squatting on all fours he was able to thrust himself up into the air, by a foot or so.

It took him maybe a half-second to sink back to the floor.

He tried it a couple more times, before he was satisfied. The gravity here was low, surely no more than a seventh or eighth of a G.

Right. He was still on Titan. But a Titan that was changed, out of all recognition.

…And the sun was too big.

It was the central fact he didn’t want to face.

It was so big it outsized the fat yellow sun of Earth, let alone the shrunken disc he’d observed at Saturn. And it was a deep, angry red. He thought he could see spots, gigantic black flaws, sprawled across its disc.

He could only think of one way the sun could have gotten so big, so red.

By getting old.

Oh, shit, he thought. I am a long way from home.

It was all too big, too much. He was a scared, naked primate, stranded in an alien future… He could do a Bill Angel, retreat into some dark primitive recess he’d brought with him, all the way from the past…

The hell with that. Think, Rosenberg. Categorize.

He thought about the gravity. The waves.

All that proved the laws of physics were still working. And he could still figure things out. Even run experiments, test hypotheses. Hang onto that, Rosenberg. Whatever the hell is going on here, science still works. I can figure it out.

Anyhow, isn’t this what I wanted? To cheat death — to see how it all came out in the end?

…But, deep down, he had expected some kind of team from Earth to retrieve them, human faces peering over some kind of hospital bed.

Not this.

He wanted to curl into a ball, retreat into sleep and incomprehension. But if he did, he might never come back out.

His shadow, blurred by its passage through the bubble wall, fell over the corrugations, shortened by the high angle of sunlight.

He tried to feel the corrugations through the bubble material, but the stuff wasn’t flexible enough to give him any real sense of touch. He thought he could see something of a cellular structure, though: there was a crude graininess to the corrugations, lumps maybe the size of rice grains. Cells, maybe. The surface looked almost porous, where he could see it closely. There were beads of some liquid gathered there, and a crusty, solid deposit…

I bet that solid’s cyanogen. His mind raced. This is some kind of animal.

Ammonia life?

Come on, Rosenberg, you know the theory. His huge steed must drink ammonia, respire by burning methane in nitrogen. But cyanogen, the carbon dioxide analogue, was a solid at these temperatures. And so the hide of this creature was dripping with ammonia, and crusted with cyanogen waste.

In that case, he thought with growing excitement, he had to be rising out of an ammonia ocean, polluted with complex, melted hydrocarbons. There must be some form of photosynthesis going on here: ammono plants, using solar energy to turn respiration products — ammonia and cyanogen — back to methane and nitrogen, closing the matter loops. But cyanogen could only circulate in solution, not as readily as gaseous carbon dioxide in the air of Earth. That must mean the photosynthesis-analogue was going on in the oceans — some kind of plankton equivalent there. Perhaps there were no land-colonizing plants here…

Perhaps the creature whose back he rode was the flowering of the ammono-based life forms whose prebiotic chemicals he had glimpsed near Tartarus Base.

It was as he’d predicted to Benacerraf. It was Titan summer.

How about that. A hell of a lot to deduce from a few grains of cyanogen, Rosenberg. But it was comforting, hugely so, to be able to figure stuff out. And—

And the surface under him lurched. His bubble rolled. He tried to grab at the yielding wall but could get no grip. He slid down the wall, his chest rubbing against the soft, warm material, and finished on his front at the base of the bubble.

The bubble stabilized again. He climbed back up to his knees.

Beyond the rim of the corrugated surface, the ocean was receding from him rapidly, its oily ripples diminishing, and he could see the reflection of the swollen sun as a disc on the sluggish surface. His bubble sat on the back of a mass of flesh, maybe a hundred yards wide, a big flattened sphere. Those complex bruised-purple corrugations spread all the way to the rim. Maybe the creature needed a lot of surface area, for its bulk.

He could see a shadow sailing over the ocean surface. It was the shadow of his huge steed. There were ropy objects trailing beneath, maybe tentacles, waving passively in reaction to the breeze of the flight…

The shadow was under him. The damn thing was flying, now, like some immense chewed-up balloon. He was riding a jellyfish the size of a football field, as it flew through the green air of a new Titan…

Wonder battled with fear, threatening to overwhelm him. He longed to be enclosed: he longed for the cozy warmth of his EMU, the tight metal walls of the hab module.

…So how was it flying? He couldn’t see any wings, jets, propellers.

Anti-gravity?

Think, Rosenberg. Look for the simple explanation.

The thing was probably buoyant. Simple gas-bags, somewhere within this fat structure, would be sufficient to lift the jellyfish from the ocean, and up into Titan’s thick air.

There was something else riding the back of the jellyfish, about twenty yards from him.

It was another bubble, resting like a drop of water on the back of the ammono creature.

He threw himself at the wall of his translucent cage and stared across. It was like trying to see inside a droplet of scummy pond water.

He thought he saw something in there, an inert white form.

He shouted, banging on the wall of his bubble. He even tried to roll forward, within the bubble, to make the whole thing roll across the jellyfish, like a hamster in a plastic ball. But the bubble resisted his efforts.

His mind seemed to dissolve. To hell with the red giant sun, the new biosphere. All he wanted was to reach that other human being.

He was soon panting, his hairless flesh coated with a sheen of sweat.

He gave up.

Even if he’d got over to the other bubble there wasn’t anything he could have done to reach its occupant. If he could somehow breach this bubble — even if the temperatures outside were tolerable — the air of this new Titan was surely toxic, laced with hydrogen cyanide and ammonia.

But it was sure as hell worth a try.

He was finding it harder to breathe.

He felt an uncomfortable pressure in his bladder. He needed to take a piss.

He looked around. There just wasn’t anywhere to piss into, inside this sheer-walled, seamless bubble.

He tried not to think about it. But of course that didn’t help.

In the end, he just stood up in the center of the bubble, grabbed his dick, and let go. What else could he do? Warm urine splashed up over his feet. A puddle gathered at the lowest point of the bubble floor, green and frothy, and he stepped back quickly, trying to keep his bare feet out of it.

When he was done he retreated to the wall of the bubble, watching the urine lake. It spread slowly over the bubble floor, quivering as the jellyfish surged smoothly.

A shadow, wide and long, swept over the bubble.

Rosenberg flinched, raising his hands over his head, cowering naked against the floor of the bubble.

It was as if a roof had spread over the jellyfish, a ceiling of translucent, leathery skin, green-tinged; where the sun shone through, Rosenberg could see a coarse graininess, a sketchy skeletal structure.

The skin ceiling moved away, and sunlight, suddenly bright again, shone down into the bubble.