When they were side by side, maybe thirty yards apart, Angel started to toil upwards alongside her. Singing.

“Where did you learn the song, Bill? The Air Force?”

Again, that switch-like cut-off. “Nope,” he said.

“Then where?”

“My father. Dad would take me walking in the hills. I’d scramble along behind him, over scree and bare rock…” Angel laughed. “That old bastard would walk me until my feet bled into my sneakers.”

Benacerraf frowned. “It sounds kind of hard.”

He tilted towards her, and, through his visor, she could dimly make out his sunken eye sockets. “You’re not some Freudian, are you, Paula? Did my dad’s cruelty make me what I am? Was his ghost there to push me aboard Endeavour that last time? Is it his fault I went crazy half-way to Saturn?”

Benacerraf felt out of her depth. Was he really being so self-reflective…? or was even this remark just another thread in the tapestry of his irrationality?

She said, “What do I know? All I said was it seems tough, to drag some little kid over the kind of terrain you’re talking about.”

“Maybe. But I learned a hell of a lot.”

“Like what?”

“Like how to endure. You see, you got to have some kind of mantra, to get you through experiences like this, Paula. Crap that just goes on and on. You can sing, you can fantasize about sex, you can talk to yourself. Anything, to take your mind off what you got ahead of you, the pain in your feet and legs.”

“It sounds like auto-hypnosis.”

“Maybe it is. Mind-travelling, my dad called it. Seventy percent of any climb is mental. If you’re going to get through a slog like this, you got to fight the demons inside. Maybe you should take a leaf.”

“Maybe,” she said.

Within a couple of minutes, Angel had resumed his singing.

She considered switching off his loop. But if she did that, she couldn’t tell if he was in difficulty. She compromised. She turned down the gain, so Angel’s voice was reduced to a kind of bass insect-whisper.

Soon her shoulders, back, feet and crotch were aching again, and her body was telling her it wanted to stop, now.

Maybe I ought to try it, she thought, Papa Angel’s patent balm for the soul.

Always a little further, pilgrim, I will go. Always a little further…

Oddly, it seemed to work. Her thoughts started to diffuse, and she entered a kind of orange, mindless tunnel, of pain and effort and tholin slush that stretched on, up the hillside above her.

Always a little further.

After a time, the going underfoot seemed to be getting a little easier. She didn’t sink quite so far into the gumbo, and it wasn’t so sticky when she tried to lift up her snowshoed feet.

Then, at last, she felt a scrape of some more resilient surface under her aluminum snowshoes.

She stopped, and leaned into her harness. She tipped up her foot and dug at the gumbo with the lip of her snowshoe. There was some pale grey substance, like fine gravel, mixed in with the purple-brown gumbo.

“Hey, Bill,” she said.

“What?”

“I think I found ice.”

He laughed. “I been crunching over some shit for a hundred yards or more.”

She looked up, tipping to balance the mass of her pack.

The slope pitched up before her as steeply as ever. But now she could see that the purple-brown gumbo layer had been washed away, exposing grey-white streaks beneath. And when she leaned back to look further up the slope, she saw the surface turned into an almost pure white, streaked here and there with tholin rivulets. The white continued all the way up through the orange air, until it disappeared into the lid of grey-black methane cloud which hid the summit of Mount Othrys.

“How about that. Rosenberg, I think we did it.”

“You found bedrock?”

“Water ice.”

“How high are you?”

Benacerraf was carrying an altimeter, cannibalized from one of the Apollos; she wore it on a chain that dangled from her backpack. She reached around clumsily, and pulled the altimeter up before her face.

“A shade over three thousand feet,” she said.

“Good,” Rosenberg said.

“Good?”

“Sure. You’re well above the limit altitude of the rain. It only rains on the summits, never on the plains. It’s just what I would have expected…”

“Theory later, Rosenberg,” Benacerraf said.

“It’s just nice when you figure something, and it works out. Makes the Universe seem a little less scary.”

She let herself out of her harness, and made sure her sled wasn’t going to slide back on down the gumbo. Then she walked forward, until the gumbo beneath her feet had thinned out, and she was stepping on bare ice. She kicked off her snowshoes, and left them at the edge of the gumbo.

The ice surface wasn’t hard; it crunched beneath her booted feet, the noise sharp in the thick air.

She looked around. “The edge of the gumbo is quite sharp,” she reported to Rosenberg. “I guess we could feel it thinning out for a few hundred yards. But it’s clearly keyed to the altitude and its edge is a definite line. Like a tree line.”

“A gumbo line,” Angel said.

“The surface isn’t solid, here. It’s some kind of regolith. The ground here is very fine-grained. Almost powdery, not like ice at all. I can kick it up loosely with my toe, and it is sticking in fine layers to my boots.”

“Is it supporting your weight?”

“Yes, But I sink into the surface a little, maybe a half-inch, before it compacts It’s a little like walking on even snow.”

“Snow it ain’t,” Rosenberg said. “We’re two hundred degrees below the freezing point of water here… What you’re walking on is impact-gardened regolith. Ancient ice, smashed to pieces by meteorite and micrometeorite impacts, over billions of years. Like Moon dust, pulverized to a depth of inches or feet.”

“But this isn’t the Moon,” Benacerraf said. “Wouldn’t that thick atmosphere shield out the bolides?”

“Yes. But some, the big ones, will still get through. And remember that Titan isn’t particularly geologically active; that ice has probably lain there exposed almost since Titan first accreted, four billion years ago.”

“That’s time for a lot of gardening,” Angel said. “Hey, double-dome. We could go skiing up here.”

“I wouldn’t recommend it,” Rosenberg replied drily.

She lifted up her boot. “It has a lot of cohesion. I’m leaving firm footprints here; the regolith seems to take a sharp slope, of seventy or eighty degrees. Cohesion and adhesion.”

“Probably from organic deposits on the grain surfaces,” Rosenberg said.

“It’s going to be easy to walk here,” she said. “Much easier than on the gumbo. I guess we can leave the snowshoes behind.”

Angel was walking over to Benacerraf. Free of his harness, he seemed to bounce between each step; he floated over the ice like a human-shaped beach ball, she thought, his white suit still streaked with gumbo. He looked like a floating ghost, in the murky light.

Benacerraf stared at her own footprints, crisp and sharp and white, in the virgin Titan ice.

Benacerraf and Angel harnessed themselves up once more, and renewed their haul up the ice slope. The footing was much easier, and the aluminum carapaces of the sleds scraped easily over the crisp, firm ice.

Soon their footprints stretched down the flank of the mountain behind them, partly obscured by the snail-like trails of the sleds.

The whiteness of the ice underfoot was a sharp contrast to the grey-black lid of methane clouds. Through gaps in the clouds overhead she could see the upper haze layers, a uniform orange which seemed lurid to eyes which were becoming accustomed to the Earth-like grey-white of the ice. Again, she had the disorienting feeling that she was travelling through some false-color VR landscape; Angel’s suit looked underlit by the white below, the contours of his body shaded by the burnt orange above.