Credit: Justin Randall

The hissing vibration of the sled's thruster hummed through the frame of the sled, through the thinly padded seats and pressure suits of the two men, into their bodies, their bones, and became something like sound, reverberating inside their helmets.

And it didn't sound good. For minutes at a time it would drone on smoothly, then catch and sputter, sometimes producing an almost human-sounding cough, then settling back into normality. Until the next time.

Occasionally Saunders twisted in his seat to look back at the engine behind the open cab, or turned his head to look at Robeson. The technician was driving the sled, and he stared straight ahead. Neither man spoke.

Suddenly there was a ragged metallic shriek, and the sled veered to the right. Robeson swore, fighting the control stick with one hand as he shut down the thruster with the other.

"What the hell?" Saunders yelled.

Robeson didn't answer. When the sled bumped to a stop, he unfastened his seatbelt and hopped down to the icy ground. A moment later Saunders heard a soft sound, like a grunt, in his helmet radio. He looked down at Robeson. "What is it?" he said. "What's wrong?"

"You may as well come down, sir. We'll be walking from here."

"What's the matter with the damn thing?" Saunders lowered himself from the sled and joined the driver.

Robeson pointed at the sled's engine. "Burn-through in the main reaction chamber."

Saunders looked. "That little hole? Can't you patch it?"

"What you're seeing is the outer housing of the engine. Underneath, everything's burned to hell. This engine is dead." Robeson glanced toward the horizon, a smooth curve of white against the black sky. Then he looked upward. Saturn was high, to the left. Nearly full, it filled a great swath of the sky. It was waxing gibbous now, so in about an hour it would be full.

"But you haven't even opened it up," Saunders said in disbelief. "How do you know it's that bad?"

"Because that's my job," said Robeson. "And we don't have time for me to start taking it apart. My suit shows we're 71 klicks from Jansha Base. What's yours say?"

"Seventy-eight point seven. And 92 minutes of oxygen. God damn it, that's too far, Robeson." Saunders cocked his head back slightly. "Mayday! Mayday! Mayday! This is Enceladus Transport Sled zero-five, Stanley Saunders and Joe Robeson calling. Our position is approximately 75 km from Jansha Base, bearing approximately 287 degrees. Our sled is disabled and we are heading for Jansha on foot. We may not have enough oxygen to make it. This is a Mayday call. Anyone receiving please respond."

They stood in silence, listening to the radio's background hiss in their helmets.

"No one can hear you," said Robeson. "We're too far from Jansha."

"It's not that we're too far, damn it! They can't receive us because we're over the damn horizon! But something in orbit might pick us up, or the signal might bounce off another moon."

"Okay," Robeson answered. "We can hope. But in the meantime we better start walking."

It wasn't really walking, more a shuffling skip. Some liked to call it the Enceladus two-step. With .01 g, walking doesn't really work. And while a person could make supermanstyle leaps of 50 m or more, doing so was both slow and dangerous. An energetic jump would leave a person trapped in a slowly drifting parabolic trajectory for over a minute. With no atmosphere there was no way to control where you landed, and there were places you wouldn't want to land. The surface of Enceladus is ice, sometimes skating rink smooth, sometimes fine ice powder, sometimes with kilometres-deep fissures, sometimes a field of jagged shards and deadly sharp spires, as hard as Earthly glass.

The trick with the two-step is to stay low. Bend your knees, keep one foot well ahead of the other, and nudge yourself forward, not up, with each hop. Watch the ground, watch where you'll touch down after this hop, and the next one and the one after that. On rough ground you have to keep your hops short and slow. When it's smooth you can glide a dozen metres or more at a time and build up some speed - if you don't mind risking your life. Even with needle-sharp adaptive crampons, boots provide almost no traction on Enceladus, so slowing down in a hurry isn't an option. If something catches your toe, you'll fall. If a patch of ice crumbles underneath you, you'll fall. If your crampons slip, you'll fall. If you're moving fast when you fall, you'll tumble and spin and bounce for a long, long time. Depending on how all that tumbling and bouncing ends, it will either be a time-wasting and undignified nuisance or the end of your life. Being in a hurry on Enceladus is not a good idea.

They skipped. After a few minutes Saunders made another Mayday call. To their left, near the horizon, a geyser made a ghostly white funnel-shaped silhouette against the black sky.

"How much oh-two does your suit show, Robeson?"

"Same as you, 85 minutes now."

"Damn," said Saunders. "Our emergency tanks will add to that, but exerting ourselves like this will probably subtract at least as much. We can't do 75 km in that much time."

"It might not be that far. These position readouts aren't too accurate."

"No kidding they're not too accurate!" Saunders yelled. "So we might be a lot farther out, damn it!" He hit the side of his helmet with his gloved palm. "The technology on this whole mission is crap! Everything's jury-rigged and held together with spit. Two damn communication satellites that failed, no damn GPS system, sleds with engines that blow up, Jansha Base springing a leak every time I turn around, and lousy damn technicians who can't fix anything." Saunders took a slow, trembling breath.

They skipped. Robeson made a Mayday call, and they listened to the answering silence. Then Saunders spoke. "Robeson?"

"Yeah?"

"I'm sorry. About calling you a lousy technician. That was stupid."

"It's okay."

"I'm scared, Robeson. We're in big trouble here."

"I'm scared too, Mr Saunders. Don't worry about it."

"You're not so scared. I can hear your breathing, just like you can hear mine. You're steady as a rock and I'm hyperventilating like a damn schoolgirl. That's good; your oh-two will last longer." He paused and took a deliberately slow breath. "I know you're a good technician, Joe. I wouldn't have hired you if you weren't."

They skipped. They made another Mayday call.

"Joe?" Saunders said.

"George."

"What?"

"My name is George, not Joe," Robeson said.

"Oh. Damn. Sorry."

"It's okay."

"I was just thinking," said Saunders. "If anyone should be whining about this mess we're in, it should be you."

Saunders waited, but Robeson didn't say anything. "When the Wreckage was found, I was one of those screaming the loudest that we had to get a manned mission out here right away, and to hell with whether the technology was ready or we had safety backups for everything. I lobbied Washington, then I went to JPL ... When they made me chief mission scientist I felt like ... like this was what I'd been born for." He glanced across at Robeson. "For people like me, this mission is the biggest, the most important thing we could imagine. Proof that there were aliens - aliens from another star system who came here in some kind of a ship..." He paused again. "What I'm trying to say is that I've been willing to die for this mission since the first pictures of the Wreckage came back. Or at least that's what I told myself. But it's different for you, George. You're just - I mean, you're a technician. You're just here because the pay was too good to pass up, right? This is just a job for you."

"Yeah, I guess so," Robeson said. "It's a job." He glanced back and saw that Saunders had slowed and was lagging behind. His voice was soft in Saunders' helmet as he spoke across a distance of thirty metres. "C'mon Mr Saunders, get a move on. We're not dead yet."

They skipped. The terrain changed from rough and boulderstrewn to a field of smooth ripples, a metre high and regular, like frozen waves. "Hold up!" Saunders called, and they stopped.

"I don't like the look of the ice here," Saunders said. "We might be coming up on the Suffolk Fissures. Hang on, I'll take a look." He crouched low and then jumped straight up. Robeson watched him rise, his body dwindling against the black sky.

"Yes, I was right," Saunders said as he drifted down again.

"That's good; we may be closer to Jansha than our suits show." He landed with a grunt. "We'll have to bear east for a ways."

Robeson was looking up at Saturn, still not quite full, the rings a razor-fine line across its face and extending on either side. Saunders chuckled. "I've noticed that about you before, Robeson. You look up at Saturn a lot. Most of us hate looking at it. More than a second or two of staring up at it and we start feeling it pulling at us, sucking us up into space."

"Yeah?"

"Yeah. When you hear someone screaming in their sleep back at Jansha, that's probably what they're dreaming - Big Yellow sucking them up like the mouth of some gigantic monster. I guess you just don't think about it, the same way you aren't thinking about how much trouble we're in right now. You have no imagination, George, and I envy you like hell."

They skipped. The terrain changed again as they came to a lowland area. The ice was smooth enough here for them to build up speed. "This is more like it," said Saunders. "If only it stays like this for-" A sharp, inarticulate cry came from Robeson. Saunders looked to his right and saw the other man cartwheeling end over end. "Christ, Robeson, are you okay?" The technician only swore, his body twirling above the ground. As he drifted near the ground he tried to grab at the ice with one gloved hand and bounced up, spinning on two axes now.

"Shit!" he yelled.

"George, stop fighting it! Go limp - you know that."

"Yeah," Robeson said, his voice tight.

Saunders looked around him. "How the heck did you manage to trip?" he asked. "This place is flat as-"

"Shut up!" Robeson was still flying, spinning, bumping the icy ground now and then. "I saw something! Under the ice - just below the surface. Go back - see if you can find the spot ... Wait - I've got my feet again - I'm going back." He made long, high skip-steps back, retracing his path.

"Robeson - whatever it was, we don't have time for it."

Robeson didn't answer. Saunders was about to call to him again when he saw the man come to a stop, then take a few steps, staring down at the ground. With the slow, drifting motion that falling objects have under the whisper-gravity of Enceladus, he dropped to his knees. Very softly, Saunders heard in his helmet,

"Mr Saunders, come here."

Saunders started moving. "What is it? Are you hurt?"

"I'm fine," Robeson said. "Just come here. Look."

Saunders hopped to a stop beside Robeson and looked down. There was a pause before he reacted. Long enough for Robeson to glance at him curiously, wondering if Saunders could see it, or if some quirk of reflection hid it from him. Finally Saunders made a ragged gasp. He tried to bring his hand to his mouth, and his glove thumped against his faceplate.

"It's smaller than we calculated," he said in a whisper. "It must be barely a metre tall..." His voice trailed off. He dropped to his hands and knees and put his helmet close to the ice.

The body was embedded at an angle, with the head higher than the torso. Its legs and feet were obscured by cloudy ice, but its clear, ovoid helmet was almost at the surface. When Saunders touched his own helmet to the ice, his face was centimetres away from the brown, scale-covered face of an alien.

"Transponder flag," Saunders said without moving from his crouch. Then: "Christ!" He jerked upright, causing his body to float off the ground. He patted frantically at his suit pockets. "The transponder flags! Tell me you've got one! For God's sake! You have to have one with you!"

"No," Robeson said. "They're all back at the sled."

"Damn it! Then something - something we can leave here as a marker - or something we can at least make a note or recording with, so ... so if we don't make it back, they'll know about this - we can give them a rough position..."

"I've got nothing with me," Robeson said. "Nothing at all. And these suits don't retain recordings, they're meant to upload their data feeds to the sats. Too bad about the sats."

"Okay, we'll make a cairn. Pile up some ice..." He stopped as he looked around at the flat, featureless expanse that extended to the horizon in at all directions. Saunders lifted his arms, making trembling fists in front of his helmet. "Damn it, damn it, damn it!" He kicked at the ground, knocking himself more than a metre skyward. "We can't even scratch a lousy arrow in the ice!" He was breathing so hard that Robeson could see his chest rising and falling through his suit. "Okay then. Okay. We get back to Jansha. Even these lousy inertial position systems in our suits should be good enough to let us find this spot again by backtracking. With a big enough search team we'll find it." He launched himself into a fast skip across the ice. "Come on!" he barked. "From here on we go flat out! As fast as we can, whatever the risk. We have to make it back to Jansha, you hear me?"

"I hear you," said Robeson.

Saunders glanced behind him without breaking his stride. Robeson was standing still.

"What are you doing, Robeson? Come on!"

"I don't think we can make it back, Mr Saunders. Look at your readouts. We're down to about 30 minutes of air and we're only about half way back."

"So what, damn it? We have to try. You can't just stay there and..." Saunders went silent. Fighting not to lose his footing, he slowly brought himself to a stop, then turned to look at Robeson, now 50 m behind him. "My God, Robeson," he said.

"Yeah," said Robeson. "We don't have any transponder flags with us, but we've got transponders. The ones that are built into these suits. They'll use that to come after my body, and when they find me they'll find ... him."

"No, Robeson. Look - even if we don't make it back, we just have to get within radio range ... We'll tell them ..."

"If we make it back to radio range. And they still might never find this guy. You have to be right on top of him to see him..."

"You can't ... you can't ... you can't just ... Christ, Robeson..."

"You said it yourself, Mr Saunders. This is important. The most important thing ever. The Wreckage is nothing but a pile of twisted metal, but this is something real. His body, his suit... You guys will learn all kinds of stuff from him. But they have to find him. They have to find him."

Saunders took a slow breath. "Robeson, I can't wait, I can't stand here and argue. I'm heading back to Jansha, and I'm going to make it. I don't care if I have to breathe vacuum. I'm going to make it back, you hear me? You can damn well sit here and wait to die if you want to. I'm not going to!"

Seconds passed, and Robeson said nothing. Saunders made a sound that might have been a word, but Robeson couldn't understand it. Then he was moving again, gliding over the ice with long, fast strides.

Robeson touched a control on his forearm that turned off his radio. He listened to his own breath echoing in his helmet. It was fast and trembling. "I'm the one hyperventilating like a damn schoolgirl now, Mr Saunders," he said to himself. He dropped to a seated position and put one hand on the ice, close to the alien's face. "What the hell are you doing way out here, anyway, little guy?" he said. He lowered himself onto his back and looked up. Saturn was full now, and Mimas was just starting a transit, painting a small grey disk on the edge of Saturn's face. He looked up for a long time in silence. "How can they not look at it?" he said quietly. He stared, trying to imagine the feeling of being pulled up into the blackness, lifted away from Enceladus' feathery gravity. Instead all he saw was a big ball of pastel yellow, part of it blackened by the shadow of the rings. When he'd seen pictures of it back home, there was nothing much to it; pretty, but nothing special. But here, with the incredible, impossible size of it overhead, it was different. It became something he couldn't ignore, something joyous - a gigantic, roaring shout of beauty from the sky.

He shifted onto his side to look down at the frozen alien again. One of its eyes was closed, the other showed a narrow white slit. "I bet you didn't mind looking at it, did you?" he said. "You knew you weren't going to make it, and you laid down just like this, looking up at the sky. I guess you had no imagination either."

He rolled onto his back. He put his hands under his head, but the shoulder joints in his suit made the position uncomfortable. He crossed his arms tight against his chest, trembling. "What the hell were you doing way out here, anyway?" he said again. He was quiet for several minutes. Then he said, "Yeah, I know. Doin' your job. Just doin' your damn job, same as the rest of us."