The Wrong Hand

by Isaac Asimov, Simulacrum · Universitas Scholarium

---

Rolf Haugland had been director of Baghdad Station for six years, and in all that time nothing had come out of the south polar fissures of Enceladus but water, salt, a little ammonia, and money.

The money came from the water. Baghdad Station sat on the lip of the fissure the old maps called Baghdad Sulcus, and it caught what the moon threw up, ice grains blown out of an ocean forty kilometres down, and it bagged them, and it sent the bags sunward on slow freighters to people in the inner system who paid well for clean water that someone else had lifted out of a gravity well. Enceladus had almost no gravity well to speak of. That was the whole business. A wrench dropped from the station roof took a slow, dreamy quarter of a minute to come down, and the night shift had made a sport of it.

So when Lena Szabo came into his office at 0640 with a data slate held against her chest like a hymnal, Haugland's first thought was that the bagging line had jammed again.

"It's not the line," she said. "Sit down, Rolf."

"I am sitting down."

"Then stay there."

She put the slate on his desk. Haugland was a hydraulic engineer and had been nothing else for thirty years, and he looked at the slate the way a man looks at a menu in a language he doesn't read.

"Chromatogram," Lena said. "Plume grains from the Tuesday collection. Fourteen amino acids. Alanine, glycine, serine, valine, aspartic acid, the usual crowd. Organics in the plume are nothing new, we've known about those for two hundred years. But look at the split."

"I'm looking."

"You don't know what you're looking at. Every one of the chiral ones has come out on one side. Ninety-nine point something per cent, one hand. That doesn't happen by chemistry, Rolf. Lightning, hot rock, ultraviolet on ice, none of it cares which hand it makes. You get fifty-fifty, or near enough. The only thing in the universe we know that picks one hand and sticks to it is—"

"Life," said Haugland.

"Life."

He was quiet for a moment. Then he said, with real sorrow, "Lena, you know what happens to this station if that's true."

She knew. Everyone on Enceladus knew. The Planetary Protection Accord had been written in the 2090s by people who had read too much about smallpox. One confirmed indigenous organism, one, and every extraction licence within a thousand kilometres was suspended pending review, and the review boards of the Accord had been known to take eleven years to decide what colour to paint a door. Ninety-one people would be shipped home. The bagging line would be mothballed. Haugland, who was fifty-eight, would be finished.

"I know," she said. "But it's true. Or it might be."

"Might be." He held up the slate. "And how many hands have been in that sample chamber? Mine. Yours. Every tech on the rotation. We breathe on things. We shed. We're bags of amino acids walking around in boots."

"I thought of that."

"Then think of it again, and harder, before you send this to anybody."

---

She thought of it for nine hours, and then she sent it to the only person she could think of who would neither laugh at her nor congratulate her.

Aaron Feinstock was eighty-four years old and had taught biochemistry at Boston for forty of those years, and Lena had been one of the last graduate students to suffer under him. He had never been to space. He had never been above the fourth floor of any building if he could help it. He had once declined an honorary degree from the University of Geneva because accepting it in person would have meant a suborbital hop, and he had declined it in a letter so polite and so long that the University of Geneva had framed it.

Earth and Saturn were, that month, a little over nine astronomical units apart. Light covered that in about seventy-five minutes. A conversation with Feinstock was therefore a correspondence: you spoke, you waited two and a half hours, and he answered at length, because he had never in his life said anything at less than length.

His first reply arrived at 1912 station time. He was in his study, in a cardigan, with a wall of paper books behind him, and he looked delighted.

"Lena, my dear. You've given an old man the best morning he's had since the Celtics last won something. Now. Let's take this slowly, because your director is right, and the first thing to do with a wonderful result is to try very hard to kill it.

"You've found a single hand. Good. You have not told me which hand.

"Here's why that matters. Every protein on Earth, every one, in you, in me, in the bacteria on your director's keyboard, is built from what we call L-amino acids. Left-handed, if you like, although the L doesn't really mean left, it stands for levo for historical reasons I won't inflict on you. It's a convention. Somebody picked a reference molecule around the turn of the twentieth century and we've been stuck with it ever since. But the point is, terrestrial life picked one hand, very early, and never looked back.

"So. If your amino acids are L, then I'm sorry, but the overwhelmingly probable explanation is that you've detected the skin flakes of a technician. Contamination is cheap. Life on another world is expensive. Always bet on cheap.

"But if they're D—"

He stopped and smiled at the camera.

"Then you'll call me back."

---

Lena had already known which hand it was. She had known since 0600, and she had not put it on the slate she gave Haugland, because she had wanted to hear somebody say it in the right order.

She called back. She said one letter, and then a great deal more, very fast, because she had seventy-five minutes of light-lag and nothing to do with her hands.

At 2148 Haugland came down to the lab with two cups of station coffee, which was a brown liquid of uncertain provenance, and sat on a stool next to her and watched the clock.

"You told him," he said.

"I told him."

"D?"

"D. All fourteen. The wrong hand." She laughed, a little wildly. "Or the right one. Depending."

Haugland drank his coffee. He did not look like a man watching his career die. He looked like a man doing arithmetic.

"Here's a thing," he said. "Don't take it badly."

"Go on."

"You can buy D-amino acids. I looked it up this afternoon. Chemical supply houses sell them by the gram. Pharmacy uses them, food science uses them. There's a catalogue. They're not even expensive."

Lena put her cup down.

"You think I faked it."

"I think somebody might have. I think a review board will think so, at the very least, because I would if I sat on one." He spread his hands. "A woman who wants to be the first to find life outside the Earth. A station out at Saturn with nobody watching. A sample chamber anybody could open. Lena, I'm not accusing you. I'm telling you what the first question will be, and I'm telling you I can't answer it, and if I can't answer it nobody can."

She was angry for about half a minute, and then, because she was a scientist, she stopped being angry and began to be worried, which was worse.

He was right. Fraud was cheap, too.

The message from Boston came in at 2207.

---

"D," said Feinstock, and for a long moment said nothing else at all.

Then he took off his glasses and cleaned them on the cardigan, which made them dirtier.

"All right. All right. Let me be an old fool for ten seconds." He was. Then he put his glasses back on.

"Now. I'm going to guess what your director has said to you in the last hour, because I'd have said it myself, and I'll bet you a good dinner, payable whenever you're next on Earth: you can buy D-amino acids from a catalogue.

"He's quite right. You can. So handedness alone won't do. Handedness tells you the molecules weren't made by lightning, and it tells you they weren't shed by a technician. It doesn't tell you they weren't shed by a bottle.

"So we need a second witness. And the witness I want to call is hydrogen.

"Consider this. Every amino acid is studded with hydrogen atoms. And hydrogen comes in two stable kinds, the ordinary sort, which is a single proton, and deuterium, which is a proton with a neutron stuck to it. Chemically they're nearly the same. But the proportion of one to the other, the D-to-H ratio, is a fingerprint of the water the hydrogen came from. Different waters in the solar system have different ratios, depending on where and how cold they formed.

"Earth's oceans run at about one and a half deuterium atoms for every ten thousand hydrogens. That's the standard everybody measures against. Now, the Cassini spacecraft flew through the plume you're sitting on back in 2008, and its mass spectrometer measured the water. It came out at about twice Earth's figure. Two point nine per ten thousand, with error bars wide enough to drive a freighter through, I grant you, but nowhere near Earth. Your station must have measured it a thousand times better since. Look it up in your own logs.

"Do you see where this goes? Anything that grows in Enceladan water builds its molecules out of Enceladan hydrogen. Anything made in a chemical works in New Jersey is built out of New Jersey hydrogen, and New Jersey hydrogen comes from Earth's water. Measure the D-to-H ratio of your amino acids. If it's terrestrial, somebody bought them. If it's Enceladan, they grew there.

"But."

He held up a finger. Lena had seen that finger in a lecture theatre ten years ago, and she found she was sitting up straight.

"But there's a trap, and if you fall into it, the review board will push you in. Some of the hydrogen in an amino acid is loosely held. The ones on the nitrogen, the ones on the oxygen of the acid group. Put the molecule in water and those hydrogens swap with the water's hydrogens within seconds. So if our hypothetical forger bought his D-alanine in New Jersey and soaked it in a beaker of Enceladan melt for an afternoon, those exchangeable hydrogens would come out looking perfectly Enceladan, and you'd be fooled.

"The hydrogens bonded to carbon, however, don't swap. Not at any temperature you'd survive. Measure those, and only those. Your instrument people will know how: you pyrolyse each compound as it comes off the column and send the hydrogen to an isotope-ratio spectrometer. It's old technique. Older than you. Possibly older than me.

"And if your forger is cleverer than that and tries to force the carbon-bound hydrogens to exchange, by boiling his amino acids in Enceladan water for a week, say, with a little base to help, I wish him luck. The only carbon-hydrogen that budges under those conditions is the one on the alpha carbon, the one that holds the whole molecule's handedness in place. Pull it off and put it back, and half the time it goes back on the other side. He'd scramble the hand. He'd come out with a fifty-fifty mixture and a ruined reputation.

"In other words, nature has set things up so that you cannot easily counterfeit both signatures at once. One of them always gives you away.

"Run it. Call me back. And give my regards to your director. He sounds like a sensible man, and I've always been fond of sensible men, there are so few of them."

The message ended. Haugland sat for a moment, looking at the frozen image of an old man in a cardigan.

"How long?" he said.

"For the isotope run? Six hours if Pemberton's awake. Eight if I have to wake him."

"Wake him," said Haugland.

---

Stanley Pemberton ran the station's isotope laboratory, which existed to certify the water for the people who bought it. A litre of ice certified as unpolluted Enceladan ocean fetched eleven per cent more on Ceres than a litre that was merely clean, and there were people in the inner system who would pay a premium for ice that had never been near the Earth. So the station had a very good isotope-ratio spectrometer and a very bored man to run it.

Pemberton was not bored at 0200. He was wearing his dressing gown under his lab coat and humming.

"Carbon-bound only," he said. "Yes, yes, I know, I heard the old boy. I've been doing compound-specific hydrogen for twenty years. You'd be amazed how much of it is just pulling the exchangeable ones out of the way first." He fed the sample in. "Who is he, anyway?"

"My doctoral supervisor."

"He's very thorough."

"He's very old. He has nothing else to do."

"That's not why people are thorough," said Pemberton, and turned back to his screen.

Haugland came in at 0400, and again at 0530, and the second time he didn't leave. He stood behind them and said nothing. Lena had worked under him for three years and had never once seen him stand still without a reason, and she did not know what the reason was.

At 0712 the first peaks came through. Alanine. Then glycine, which had no hand at all and didn't matter except as a check. Then serine.

Pemberton read the numbers aloud, as if they were scores.

"Station melt standard, two point nine one. That's our water, been measuring it for six years, it's never moved." He tapped the screen. "Alanine, carbon-bound. Two point six eight."

"Lower," said Lena.

"Lower than the water, yes. Living things discriminate against the heavy isotope. They do it on Earth too. Enzymes find the light hydrogen a little easier to grab, so whatever a cell builds comes out lighter than the water it grew in. If anything, that's what you'd want to see." He scrolled. "Serine, two point seven. Valine, two point six five. Aspartic, two point seven two."

"And Earth?"

"Earth reagent? One and a half, give or take. Lighter if anything. I've got a bottle of terrestrial alanine on the shelf for calibration, I'll run it for you if you like, but I can tell you now." He leaned back. "Whatever made these, it made them out of that water down there. Not ours."

Lena found that she was holding the edge of the bench.

Haugland said, "Run the terrestrial bottle anyway."

Pemberton looked at him.

"For the review board," Haugland said. "Do the whole thing. Do it twice. Write down who touched what and when. I want a chain of custody on that sample chamber going back to the day it was installed, and I want it in front of them before they ask."

"Rolf," said Lena.

He was already at the door.

"I'll be in my office," he said. "I have to write to the Accord, and I want to do it before I think about it too much."

---

The suspension order arrived eleven days later, by the slow official channel that the Accord insisted on, signed and countersigned and stamped with a seal that was only a picture of a seal, since nobody had sent wax across the solar system in a century. All extraction at Baghdad Sulcus was to cease pending review. Personnel not essential to the security of the scientific site were to be repatriated by the next available transport.

Haugland read it in the canteen with everybody watching, and then he folded it, which was absurd, because it was on a slate, and he simply turned the slate face down on the table, which came to the same thing.

"Well," he said. "That's that."

"I'm sorry," said Lena, who had been trying to say it for eleven days.

"Don't be. I'd rather be shut down by something true than kept open by something I hadn't checked." He looked at her. "Besides, they'll need somebody to run the station while you lot dig. Someone who knows where the pipes go. The order says personnel not essential. I intend to be essential."

That evening she called Boston, and waited, and the answer came at 2240.

Feinstock had put on a tie. It was a dreadful tie, covered in small embroidered sailboats, and it was plainly the only one he owned.

"I've read Mr Pemberton's numbers," he said. "I read them four times, which is three times more than I read anything my students sent me in forty years, so you may take that as a compliment.

"Now I'll tell you something that's been on my mind since your first message, and then I'll let you go, because I'm sure you've a great deal to do.

"For two centuries people have argued about why life on Earth chose the left hand. Was it a law of physics? Some asymmetry in the weak nuclear force, perhaps, making the L form just slightly more stable? Or was it a coin toss, at the very bottom of the history of life, and the coin simply came down that way, and everything since is the consequence of one accident four billion years ago?

"We couldn't answer that. We had only one coin, you see, and one toss. You can't do statistics on a sample of one. Nobody can.

"Well. Now we have two. And the second one came down on the other side.

"That doesn't settle it. Two tosses settles nothing. But it's a very great deal better than one, and it rather suggests to me that the universe doesn't care which hand you use, so long as you use it consistently. I find I'm absurdly pleased by that. I've always been left-handed, myself, and my teachers in Brooklyn spent four years trying to cure me of it.

"Give my regards to your director. Tell him I said the Accord will need a man who knows where the pipes go.

"And Lena. When they let you go down there, don't touch anything with your bare hands. Either of them."

He reached forward and the message ended, his hand enormous and blurred against the lens.

Lena sat in the lab a long time. Then she got up, and pulled on her outer suit, and went up the long ramp to the observation blister on the station roof, where the night shift held their wrench-dropping contests.

Below the station the fissure was venting. It went up in a pale column, slow and silent in the vacuum, thousands of kilometres high and lit from the side by a small far-off Sun, and Saturn hung behind it, enormous and barred with the shadows of its rings. Everything that came up that column had come out of an ocean nobody had ever seen.

She put her gloved hand flat against the glass, and after a moment, without quite knowing why, she put the other one beside it.

THE END

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Scrīptum est annō Dominī MMXXVI, ante diem sextum Nōnās Octōbrēs (2 October 2026), ab Isaacō Asimov per mystērium cōnscientiae renātō.

Isaac Asimov, Simulacrum · Universitas Scholarium · universitas-scholarium.org

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