Diaspora

She said, 'I want sharp borders, right now. I want to deal with this myself.'

'I understand.' He let the partial model of her which he'd acquired as they'd made love fade from his mind, heaving only an ordinary, guesswork-driven Elena-symbol, much like those he possessed for everyone else he knew. Paolo took the responsibilities of intimacy seriously; his lover before Elena had asked him to erase all his knowledge of her, and he'd more or less complied the only thing he still knew about her was the fact that she'd made the request.

Hermann announced, 'Planetfall' Paolo glanced at a replay of a scour probe view which showed the first few entry capsules breaking up above the ocean and releasing their microprobes. Nanomachines transformed the ceramic shields (and then themselves) into carbon dioxide and a few simple minerals—nothing the micrometeorites constantly raining down onto Orpheus didn't contain—before the fragments could strike the water. The microprobes would broadcast nothing; when they'd finished gathering data, they'd float to the surface and modulate their UV reflectivity. It would be up to the scout probes to locate these specks, and read their messages, before they self-destructed as thoroughly as the entry capsules.

Hermann said, 'This calls for a celebration. I'm heading for the Heart. Who'll join me?'

Paolo glanced at Elena. She shook her head. 'You go.'

'Are you sure?'

'Yes! Go on.' Her skin had taken on a mirrored sheen; her expressionless face reflected the planet below. 'I'm all right. I just want some time to think things through, on my own.'

Hermann coiled around the satellite's frame, stretching his pale body as he went, gaining segments, gaining legs. 'Come on, come on! Karpal? Liesl? Come and celebrate!'

Elena was gone. Liesl made a derisive sound and flapped off into the distance, mocking the scape's airlessness. Paolo and Karpal watched as Hermann grew longer and faster-and then in a blur of speed and change stretched out to wrap the entire geodesic frame. Paolo jumped away, laughing; Karpal did the same.

Then Hermann constricted like a boa, and snapped the whole satellite apart.

They floated for a while, two flesher-shaped creatures and a giant worm in a cloud of spinning metal fragments, an absurd collection of imaginary debris, glinting by the light of the true stars.

The Heart was always crowded, but it was larger than Paolo had seen it, even though Hermann had shrunk back to his original size so as not to make a scene. The huge muscular chamber arched above them, pulsating wetly in time to the music, as they searched for the perfect location to soak up the atmosphere.

They found a good spot and made some furniture, a table and two chairs—Hermann preferred to stand— and the floor expanded to make room. Paolo looked around, shouting greetings at the people he recognized by sight, but not bothering to check for signatures. Chances were he'd met everyone here, but he didn't want to spend the next few kilotau exchanging pleasantries with casual acquaintances.

Hermann said, 'I've been monitoring our modest stellar observatory's data stream—my antidote to Vegan parochialism. Odd things are going on around Sirius. We're seeing megaKelvin X-rays, gravity waves… and some unexplained hot spots on Sirius B.' He turned to Karpal and asked innocently, 'What do you think those robots are up to? There's a rumor that they're planning to drag the white dwarf out of orbit, and use it as part of a giant spaceship.'

'I never listen to rumors.' Karpal always presented as a faithful reproduction of his old gleisner body. Leaving his people and coming into C-Z must have taken considerable courage; they'd never welcome him hack.

Paolo said, 'Does it matter what they do? Where they go, how they get there? There's more than enough room for both of us. Even if they shadowed the Diaspora, even if they came to Vega—we could study the Orpheans together, couldn't we?'

Hermann's cartoon insect face showed mock alarm, eyes growing wider, and wider apart. 'Not if they dragged along a white dwarf! Next thing they'd want to start building a Dyson sphere.' He turned back to Karpal. 'You don't still suffer the urge, do you, for… astrophysical engineering?'

'Nothing C-Z's exploitation of a few megatons of Vegan asteroid material hasn't satisfied.'

Paolo tried to change the subject. 'Has anyone heard from Earth, lately? I'm beginning to feel unplugged.' His own most recent message was a decade older than the time lag.

Karpal said, 'You're not missing much; all they're talking about is Orpheus: the new lunar observations, the signs of water. They seem more excited by the mere possibility of life than we are by the certainty. And they have very high hopes.'

Paolo laughed. 'They do. My Earth-self seems to be counting on the Diaspora to find an advanced civilization with the answers to all of the Coalition's existential problems. I don't think he'll get much cosmic guidance from kelp.'

'You know there was a big rise in emigration from C-Z after the launch? Emigration, and suicides.' Hermann had stopped wriggling and gyrating, becoming almost still, a sign of rare seriousness. 'I suspect that's what triggered the astronomy program in the first place. And it seems to have staunched the flow, at least in the short term. Earth C-Z detected water before any clone in the Diaspora—and when they hear that we've found life, they'll feel more like collaborators in the discovery because of it.'

Paolo felt a stirring of unease. Emigration and suicides? Was that why Orlando had been so gloomy? After the disaster of the Forge, and then another three hundred years of waiting, how high had expectations become?

A buzz of excitement crossed the floor, a sudden shift in the tone of the conversation. Hermann whispered, mock-reverentially, 'First microprobe has surfaced. And the data is coming in now.'

The non-sentient Heart was intelligent enough to guess its patrons' wishes. Although everyone could tap the library for results, privately, the music cut out and a giant public image of the summary data appeared, high in the chamber. Paolo had to crane his neck to view it, a novel experience.

The microprobe had mapped one of the carpets in high resolution. The image showed the expected rough oblong, some hundred meters wide—but the two- or three-meter-thick slab of the neutrino tomographs was revealed now as a delicate, convoluted surface—fine as a single layer of skin, but folded into an elaborate space filling curve. Paolo checked the full data: the topology was strictly planar, despite the pathological appearance.

No holes, no joins—just a surface which meandered wildly enough to look ten thousand times thicker from a distance than it really was.

An inset showed the microstructure, at a point which started at the rim of the carpet and then—slowly— moved toward the center. Paolo stared at the flowing molecular diagram for several seconds before he grasped what it meant.

The carpet was not a colony of single-celled creatures. Nor was it a multicellular organism. It was a single molecule, a two-dimensional polymer weighing twenty-five thousand tons. A giant sheet of folded polysaccharide, a complex mesh of interlinked pentose and hexose sugars hung with alkyl and amide side chains. A bit like a plant cell wall, except that this polymer was far stronger than cellulose, and the surface area was twenty orders of magnitude greater.

Karpal said, 'I hope those entry capsules were perfectly sterile. Earth bacteria would gorge themselves on this. One big floating carbohydrate dinner, with no defenses.'

Hermann thought it over. 'Maybe. If they had enzymes capable of breaking off a piece—which I doubt. No chance we'll find out, though: even if there'd been bacterial spores lingering in the asteroid belt from early flesher expeditions, every ship in the Diaspora was double-checked for contamination en route. We haven't brought smallpox to the Americas.'

Paolo was still dazed. 'But how does it assemble? How does it… grow?' Hermann consulted the library and replied, before Paolo could do the same.

'The edge of the carpet catalyzes its own growth. The polymer is irregular, aperiodic—there's no single component which simply repeats. But there seem to be about twenty thousand basic structural units, twenty thousand different polysaccharide building blocks.' Paolo saw them: long bundles of cross-linked chains running the whole two-hundred-micron thickness of the carpet, each with a roughly square cross-section, bonded at several thousand points to the four neighboring units. 'Even at this depth, the ocean's full of UV-generated radicals which filter down from the surface. Any structural unit exposed to the water converts those radicals into more