The Heart of the Comet

by David Brin

  * * *

  “Goddamn! We’re past it!”

  Carl’s amazed face intruded on a 3D design study she was changing. He had used override to break into her mainstream persona.

  “Yes. You can rejoice,” she said warmly.

  “How’d you do it?”

  “Vector mechanics, nothing tougher than that.”

  “You were marvelous!” Lani said beside Carl, her eyes wide with wonder at being alive. Virginia realized distantly that they really had expected to die.

  “I told you the probabilities,” Virginia said. “Surely you—”

  “We figured you were just cheering us up!” Carl laughed.

  “I made the calculation accessible, Carl, you dope.” Virginia sent some light chuckles to follow this sentence, reflecting that if anyone had actually checked her, they would’ve found she had in fact reported a survival probability of three to one when it had really been only fifty-two percent. But she had been sure no one would do the entire complicated calculation. In thirty years, everyone had come to rely on her, just as they counted on Saul’s bio-miracles.

  Lani was bright-eyed, expectant. “When can we go outside? I want to grow some crops in the sun again.”

  “Nearly half a year,” Virginia said seriously. She had found that people took statements more to heart if they were laced with sharper vowels and a few bass tones.

  “Never mind, we’ll have plenty to do inside,” Carl said, slapping Lani on the rump affectionately.

  Virginia knew exactly what he had in mind. It was implicit in his entire psychological profile, true, but her intuition told her more. Carl had bottled himself up emotionally for decades, and that had been crucial in the survival of Halley Core. Now time and circumstance had worked its curious magic and he was free. The youthful Carl could not—did not—respond to Lani’s quiet gifts. This weathered, wiser Carl could, and would, and should.

  Somewhere in the compacted recesses of organic memory, a twinge of humor and irony kindled. He’s getting what he needed, even if it isn’t what he wanted. Virginia made a note to cycle Lani in for a “routine” physical within forty days.

  The prickly storm swelled. Though they had survived the worst at perihelion, a residue of heat still leaked inward. Virginia sent men and women and mechs to seal tunnels which collapsed, whole zones of shafts whose walls began to sputter and evaporate.

  Warmed in vacuum, ice sublimates directly into vapor without becoming liquid. As Halley’s scarred skin blew away, Virginia began her grand experiment.

  Teams of hardened mechs ventured forth from the eroded shaft mouths. They dispersed slabs of amorphous silicates, grit and grime dried and filtered and compacted through the years of mining. Quickly they spread huge fields of linked, slate-black sheets oil well-chosen spots near Halley’s equator. They were too heavy for the subliming vapors below to push them away, and the mechs made doubly sure by hammering cables to anchor the slabs.

  The effect came with aching slowness. Halley spun now with a day of only three hours. At a precisely calculated moment, the silicate shields blocked sunlight from the ice. Over that zone, outpouring gas ebbed. Other areas continued, and this difference in thrust, combined over the turning face of Halley, began to minutely alter its orbit. Astronomers had long noted this “rocket effect” on rotating comets that temporarily exposed fields of dust, but it had always been spontaneous and temporary. Now it was done by design.

  Virginia deployed her mechs remorselessly. Some overheated and failed, others were crushed between the large sheets as they butted and swayed in the sun-driven gale of gas. At her command, they could tilt the slabs end-on, so the protected areas suddenly leaped to life, spurting amber-tinged plumes. Deftly, resolutely, she played a dynamic symphony with the furious hurricane forces that buffeted the mechs and their cargoes. For days, and then weeks, she cupped the outraged steam of Halley to new purposes. Unbalanced thrusts aligned along the comet’s orbit, a persistent hand that swept them along a new orbit.

  Four months beyond perihelion, Virginia waited for the inevitable. She had deployed fresh arrays of infrared and microwave radars, concentrated along the expected cone of the sky.

  The first was slow and tiny, a marvel of stealth technology. She got a glimpse of broad, transparent vanes that radiated away the sun’s heat. Only her phased-array microwave net, operating at ten gigahertz, picked up its faint shadow. She had spread the gossamer wire receivers over a volume spanning a hundred kilometers, to get high definition. If it had been faster she might not have been able to integrate the diverse signals in time. As it was, she crisped the snub-nosed thing ten kilometers away from Halley.

  Behind it, a few moments later, came something large and lumbering. It used the sun for background cover, superimposing itself on a vibrant-blue solar flare that had sprouted only an hour before from a large magnetic arch.

  She caught it with a laser burst, feeling a chill run through her mind. She would never have caught the slight, giveaway ripple of ultraviolet that betrayed the incoming warhead… except that she was monitoring the flare, as part of their ongoing research program. Jeffers had been right when he insisted on retaining the dedicated science diagnostics; it paid to keep learning.

  The third was fast, closing at a hundred kilometers a second, still boosting with a light-ion drive. Virginia wondered why they had left the electrostatic accelerator on, since it made the projectile much more visible. She fired at it with the newly resurrected launchers, and in the two-second delay waited confidently for a kill signature.

  None came. Her phased-array net told her why. The thing was maneuvering sideways, dodging the slugs of iron. Evidently it could pick up the microwave hum of the launchers and see the pellets as they came.

  She immediately fired all her harnessed laser banks.

  They, too, missed. By then only four seconds remained and she did not even have time to sound alarms in the tunnels of Halley.

  Desperate, she drove the power level of the of the gigahertz net up a terawatt and shifted the system from RECEIVE to TRANSMIT. The array had never been used this way. For a brief instant it could have sent a hail to a civilization across the galaxy itself, if anyone along the beam happened to be looking. The spider-web dishes could probe and pinpoint. Virginia fired a pulse of electromagnetic energy at the precise dot that swam in her triangulated worldview.

  They had safe-armed this warhead. As the electromagnetic tornado burst upon it, the chip-mind aboard fired the compressing explosives before they could evaporate. The equivalent of twenty megatons of blistering fusion energy flowered in the black sky above Halley, raising a flash-burn of ivory fog from the weathered ice.

  Throughout the battle Virginia had alerted no one. The men and women and families went on about their lives, untroubled. Only when workers on the surface wondered about the sudden flare of brilliance did she call Carl and deliver the news that their great battle had come and gone in the time it took Carl to put down his cup of coffee.

  CARL

  “Any signs of others?” Carl asked tensely.

  “None;” Virginia said. “I have extended my search to a light-hour all around us, and find nothing.”

  Lani came coasting into Central, her face drawn and pale. “I heard your announcement, Virginia. How close did they get?”

  “As the Duke of Wellington said after Waterloo…” Virginia’s voice shifted to a heavy, aristocratic British accent, “‘It was a damned near thing.’”

  “And they’ll try again, if we continue on our planned trajectory;” Carl said soberly. “They won’t tolerate us using the Jupiter encounter to loop us into the inner solar system. They’ve got years to shoot at us, remember. When we come back inward, they’ll strike again. That attack may fail, too. And the next one. But eventually…”

  “Those murderers! Lani cried. “We were willing to accept quarantine, but that wasn’t enough for them! Just to protect themselves from any chance of exposure to Halleyforms, they’d kill us all.”
>
  Carl felt the inevitability of what he had to say, the end of so many hopes. “Time to face facts. We can’t come back in from the cold.”

  Lani frowned. “But that means…”

  “Right. We’ve got to choose a trajectory that’ll take us outward after Jupiter. It’s the only way to stay out of Earth’s reach.”

  Virginia asked, “You think that will be enough to make Earth stop?”

  Carl shook his head. “We’ll have to hope so. We’ll chart a course that takes us far into the outer solar system.”

  Lani looked at him, biting her lip, silent.

  “Somehow,” Virginia said slowly, “I don’t believe they will be content with anything less than a departure orbit.”

  Lani’s eyes widened. “What? Leave the solar system entirely?”

  “Effectively.” Virginia said sympathetically, “They will then be convinced that Halleyforms will never reach Earth.”

  Carl nodded. “No point to chasing us. Too expensive, anyway.”

  “What’ll we do out there?” Lani asked incredulously.

  “We’ll live. We’ll die.” Carl stared, unseeing, at the main screen where numbers rippled. “Into the Oort Cloud…” he said distantly. “There are supposed to be trillions of iceworlds there, asteroid-sized. That’s what Halley was, before some nudge, maybe from a passing star, tumbled it into the inner system.”

  Lani asked doubtfully, “And once we’re there? Can we use those for resources?”

  He shrugged. “Maybe. We’ll have hundreds of years to think about it on the way out.”

  Lani settled into a webbing, her face composed. “We’ll all be dead before then, even with sleep slotting.”

  Carl felt an odd, distant resignation. Somehow he had known that he would never leave this place. They were consigning not only themselves, but all further Halley generations as well, to an outer darkness of limitless unknowns. Fleeing into the abyss.

  Lani said, “I suppose we must… plan for what we can do, not what we’d rather do.”

  Life’s a series of overcoming dooms, one at a time, Carl thought. He knew they could do it, too, if they simply refused to give in to despair. If we have something to live for.

  SAUL

  Year 2141

  Half of Stormfield Park had been turned into a nursery. The old centrifugal wheel had been reinforced to spin faster, providing a full tenth of an Earth gravity to help young bones grow strong. That was hard on some of the older generation, but still they came often, when off work, to listen to the high, piping voices shrieking in play and laughter.

  Saul felt that way as he walked carefully along the grass-lined, curving path at the rim of the wheel-park, where holograms gave the illusion of a cityscape just beyond a low hedge, with skies spotted with warm, moist clouds. Mothers and nursery workers tended their growing crowd of boisterous charges nearby, watching their games, admiring the infants’ clear-eyed, long-limbed beauty.

  The children had saved Halley Colony… if in no other way than by lightening the spirits of those who now knew they would never see Earth, Mars, the asteroids, or any unfamiliar human face ever again.

  We are the first starship, Saul had come to realize, two orthree centuries ahead of schedule.

  Oh, Halley was still tied to old Sol’s apron strings, but their ship home was irreversibly on course toward the outer cloud now, where trillions of iceballs drifted in the not-so-entirely-empty range between the stars. Alien ground. They would live or die on their ingenuity, and on whatever they had taken with them.

  On that subject Saul had just completed an important study, an inventory of the genetic pool available for the coming generations. The question was an important one, for it might mean the difference between the colony’s survival or a long, slow decline into degeneracy and death.

  There’s plenty, enough heterozyqosity, he had decided A broad cross section of the types that populate old Earth. It should provide enough variety. Especially with the mutation rate we can expect. The bigger problem will be maintaining a large enough population.

  Halley had enough resources, for now, to keep the colony going into the indefinite future. Deuterium mined from the ice would fire the fusion piles—now relocated out on the surface to minimize waste heat—until they managed the skill to put together a proton-power generator from one of the Phobos designs. Their skill at recycling and ecological management was already impressive, and would grow.

  If husbanded carefully, the trillion tons of ice and hydrocarbons might keep a couple of hundred humans at a time—along with their plants and animals—alive for a hundred generations or so.

  Just enough time. For in a couple of thousand years, the comet’s hurtling velocity would ebb as it approached its new aphelion, out where the Hot was only the brightest star. And out there, drifting slowly, were hundreds of billions of other great lumps of primordial matter left over from the birth of the solar system. Once their present near-hyperbolic velocity had leaked away to mere meters per second, there ought to be plenty of chances to snag other comet heads.

  Saul stopped at a point where the guardrail hedge opened at the rim of the curving wheel. He was still thinking about the images Virginia had shown him, just a few minutes ago, in the little glade beneath her tea house… a simulation of those days, so long from now, when the men and mechs of Halley would nudge their tired, depleted old home near fresh new ice-specks in the great blackness. Perhaps they would seize two, three, or more, and drift apart again on their new colonies.

  And from there? Virginia’s simulation projected no limits. The Oort Cloud was vast, and humans were noted settlers.

  And our own sun’s Oort Cloud brushes against the comet shoals of other stars…

  The image she had presented was daunting. She already contemplates in terms of aeons… it’s going to take me a lot longer to get used to thinking that way. My own style of immortality is different. It retains the feel of Time as no friend.

  He passed Lani Nguyen-Osborn, sitting on a park bench under a dwarf maple, nursing her new son. Her eldest child—little Angel Angelique—played in the grass nearby.

  Lani smiled and waved. Saul grinned. They had spoken only an hour ago when he was on his way to see Virginia. He was due to have dinner with Carl’s family later tonight. In the meantime, he still had work to do.

  The vista of an Earthy city cleared as his section of the wheel approached ground level. He stepped through the break in the guard hedge into the microgravity of Halley’s caverns, and let himself drift into the soft sand braking embankment. A cloud of particles puffed outward as he landed, then slowly settled to the floor.

  He launched off toward the exit leading to his laboratory. The half-living sphincter lock cycled him through to the tunnels with a soft, moist sigh.

  The gene-pool survey had been very good news—even if it had reminded him that neither he nor Virginia would ever contribute. All of his clones were sterile, and her physical body had long ago become part of the ecosphere.

  Perhaps it was for the best, at that. For his clones would be round as the generations came and went. The decedents of Carl and Lani and Jeffers and Marguerite would be mixing their genes, sorting and restoring until a new species of humanity emerged. If all of those “Saul Lintz” models also kept having children, over the centuries, it would muck up the process.

  Heaven forbid! He laughed at the thought. He had long ago come to terms with the irony of his situation…the clever design of his blessing and his curse.

  Now, though, another bit of research occupied him. Something even more significant. More amazing.

  Down at the end of one little-used corridor, Saul spoke a code phrase in Aramaic and a door hissed open. He slipped past the gene-crafted guard-cockatrice into his private lab. He had his neural tap socketed into place before his frame even settled horizontally onto the webbing.

  Program… Rock of Ages… hecommanded his personal computer. Colors shimmered and steadied.

  The image on the
central holo tank was of that deep, secret room down at the heart of the Weirder domain, where Suleiman Ould-Harrad had met his faith, in his own way. The horned, carved-stone bier rotated in the holographic image.

  To the right, another display showed a sample taken from that ancient rock—symmetrical fossil ribs tracing the outlines of a creature of a very ancient sea.

  More screens rippled with data, with microscopic closeups, with detailed isotopic profiles.

  For a year now. Saul had been in touch again with Earthside specialists. With Halley confirmed to be on a near-hyperbolic trajectory, the hysteria had dampened on Earth. Guilt and shame played on what passed for news channels, these days. Some of the gifts the colonists had beamed back had also deepened the feeling that contact should be maintained until the planets merged with the roiling noise of the sun and all talk between brethren ended in the hiss of static.

  The Earth scientists had worked on his data, confirming in detail what he had already worked out in general.

  Nearly five billion years ago—in one of the gassy, dust-rich spiral arms that laced the Milky Way like filmy pinwheel spokes—a young, massive, hot star had raged through its short life and exploded in the titanic outburst of a supernova. In so doing, it had seeded nearby space with glowing clouds of heavy elements, from carbon and oxygen to plutonium and osmium… all cooked up while the blue giant had coursed through its brief but glorious youth. Save hydrogen and helium, all the elements that made up the planets—and human beings—had originated in that way, from great outbursts of primeval heat and light.

  This supernova not only spewed great gouts of heavy matter into space. It also drove mammoth shock waves, which compressed the interstellar gas and dust, forming eddies and whirling concentrations.