David Brin - The Heart of the Comet

“That’s all right, Virginia. I… I’m grateful for the help.”

There was a brief pause. Then a holo-unit display to his left came alight and Virginia Herbert’s face wavered and smoothed, a replica in rich color that still hinted of salt breezes and tropical sun. Her long black hair flowed over her shoulders, slightly puffed, as if it had been hurriedly brushed just moments ago.

“I’m glad you’re not angry with me for butting in.”

“Angry!” Saul laughed. “You saved one of us, either me or this obdurate machine!”

Virginia smiled. “Well, it’s a relief to know I did the right thing. Actually, that’s pretty complicated stuff you’re dealing with there, Saul. I can’t pretend to understand any of it. I’m just a glorified numbers jockey.”

“I disagree.” Saul shook his head firmly. “You are an artist.”

Virginia ’s olive skin darkened perceptibly. Her “Thank you” was barely audible. Saul shared a long smile with her.

Virginia ’s eyes darted. “Um, if you’d like, you could come on down here and we’ll put JonVon to work on your problem. He’s a stochastic processor, you know. And I happen to believe that makes him a lot more applicable to the kind of problem you’ve got there than these old parallel precision machines.

“I’m sure we can whip up a simulation to make that one there look like a stick figure cartoon.”

Saul nodded. “Only if you let me bring a bottle, Virginia. I have a feeling we’re going to need it.”

“ Done! ” she said gladly.

As Saul was getting up though, a stretched image of Virginia ’s arm reached out across his desk—like an India-rubber man—to tap with one finger at the glowing, throbbing line of gold lettering at the top of the tall pyramid of data.

“What is that anyway, Saul? Is it something special?”

He shrugged. “Well. I guess you could say so, Virginia. It’s the chemical symbol for something called a purine base. A rather simple one, really, called adenine.”

Virginia withdrew her ghostly, representative hand. “Well, I hope it’s important. But whether it is or not, I’ll bet we’ll be taking this a whole lot farther. I have a feeling for these things, you know.”

She smiled brilliantly.

“See you down here in a few minutes, Saul. VKH out.” Her image vanished.

Saul stood still for a moment. “Yes, dear,” he said at last to the presence she seemed to have left behind. “I do believe we are going to take it quite a bit farther.”

MOLECULAR STRANDS, LIKE MULTICOLORED STAIRCASES…LIGHTING FLASHING IN THE DARKNESS…

At the simulation’s finest scale, the molecule was little more than a stylized ladder put together from standard pieces—bright, slivers of blue, green, and red—amino acids, phosphates, and simple sugars linked like ill-sorted parts of an intricate jigsaw puzzle.

The chain seemed to twist and writhe as it tumbled in a churning stream. A tracery of silvery lines stitched out electric currents, crackling unevenly through the salty fluid.

Shiny golden radicals smacked into the growing polymer. Most bounced off again in sudden flashes of light. Occasionally one knocked a fragment loose into the flow, diminishing the molecule, leaving a hanging, ragged corner. A little more often, the colliding chunk found a niche with the right shape, and stuck.

As the polymer grew, the scale of the scene enlarged, as if a camera were drawing back. A new strand joined the first, then another, twining together in a jumbled mass. The cluster fell toward a great ocher wall that loomed from below, a rusty plain pocked with jagged holes.

The edge of one of the black openings caught the molecular skein, one end draping into the gap. The cluster tipped for a few seconds, then toppled inside.

“It’s a clay… something like montmorillonite, I believe. Notice how the chain slips right into the open latticework. Only a few of the shapes being synthesized in the open stream will be able to enter this way.

“It’s an early step in the long process of selection. Some theories say it happened this way on Earth lone ago. At last the molecules are sheltered from the tumbling give-and-take of the electrified stream. Only certain radicals can get at them in there… and the shape of the cavity aligns the molecules just so. The buildup—slow and chaotic beforehand—begins now in earnest.

“Funny it being a clay, though. I would have expected it to be.something like iron oxide. But see how the peptides actually seem to catalyze the growth of new clay layers? Amazing. I’d forgotten about that!”

Virginia let Saul ramble on, sharing his excitement but too busy to reply unless he asked a direct question. Right now it was a challenge just integrating all the diverse elements in his complicated program.

She was used to bright pictures and vivid simulations anyway. No, what impressed her was the intricacy of this world of molecules and currents, of clashing atoms and chiming balance. It was a maelstrom of tiny tugs and pulls computed in a eleven-dimensional matrix space, and still the diversity of forms amazed her.

The screen showed only the most superficial part of it—the averaged sampling of JonVon’s stochastic correlator. It was the math , down below, that really kept Virginia occupied. Only occasionally did she look up to see how the images were coming along.

Right now the simulation was following the developing molecules down into their new home. They nestled into crannies in the complex clay latticework, leaving a central passage through which fresh material entered from the outside. New pieces were added, and old ones discarded as dross to float away. The shape of the still-growing chain kept changing, now as a simple helix, elsewhere doubling back on itself, switching handedness left and right.

Saul commented again.

“I’m cheating a bit, here, for the sake of speed. We’ve set up initial conditions and are letting huge numbers of simulated molecules ‘evolve,’ leaving it to your wonderful machine to pick out the most successful line out of billions… coaxing the most promising to do the best it can under these conditions.

“We’ll see if a nudge here and there can take this primitive thing and give us…”

Virginia found her job growing easier, now that JonVon’s expert system was picking up the basic rules of this game.

Or was it because Saul was getting better at his end?

They lay next to each other on a broad, web-hammock in her laboratory, each linked by cable to the intricate hardware/software unit. For Virginia it was a familiar experience, wearing a delicate induction tap and playing her fingers lightly like a pianist on the pattern keys. Saul, on the other hand, was more awkward with his controls. The bulky cortex helmet he wore lacked the compact deftness of her specially designed link.

Yet, he was getting over his clumsiness quickly. And his excitement was contagious. His subvocalised thoughts arrived directly along her, acoustic nerve.

“This is wonderful, Virginia ! Far; far more than a mere simulation program, this construct of yours explores possibilities!”

“JonVon’s processor is bio-organic, Saul. A matrix of pseudo-proteins in a filament mesh. Back home they dropped that approach years ago, because its point-error rate is pretty high. In fact, you’re treated like some sort of nut if you even talk about it, today.” She hoped none of her bitterness carried over into her words.

“Hmmm. More point errors, sure. But you can pack so many circuits into a tiny area that it doesn’t matter, does it?

Virginia felt a thrill. He understands.