The ungainly vessel sparkled in Endeavor's floodlights. The fifty-foot-long spacecraft cautiously receded from the orbiter, puffs of gas gradually increasing the separation. Bulbous tanks, exposed struts, and an aggressively unstreamlined configuration made plain that the newly disgorged ship was never meant to touch an atmosphere.
The nearby moon, around which both vessels now orbited, cast only a pale, ghostly glow—as far as the human eye was concerned. The torrents of microwaves continued unabated.
"Everyone comfy?" Windy's light tone fooled no one—she wanted, as much as anyone, to walk on the moon. But someone had to stay on the orbiter—it landed on Earth as a glider, hardly a practical approach for alighting on an airless body—and the person best able to bring the Endeavor home, if for whatever reason the lander failed to return, was the logical choice.
"Roger that, Windy," The mission commander answered for the three strapped in on the lander. "Ready to go . . . except for one final detail. Doc?"
It was a moment of high historical drama and great personal honor. The President herself—Harold Robeson's second term had expired before the lander was completed—had asked Kyle to christen the lander. She must have ordered NASA and his USAF crewmates to keep to themselves any opinions on the subject. What could possibly compare with "The Eagle has landed"? Beyond memorability, he wanted a name that conveyed hope and confidence and, despite the ship's wholly American provenance and crew, an entire world's aspirations.
The timer decrementing before him insisted that, named or not, this vessel would begin its deorbiting burn inside five minutes. "Ladies and gentlemen, I give you the good ship Resolute."
The moon-spanning circuitry very precisely, in some way yet unknown, tracked the Earth and focused a myriad of maser beams upon it. No one wanted to learn the hard way whether proximity detection could instigate a close-in defensive retargeting. So, although the tangential approach of the Endeavor had evoked no discernible response, Resolute deorbited above the night side, where the solar-powered masers were inactive. But they couldn't accomplish their mission by hiding in the dark. Speedy set them down inside a small crater, entirely unremarkable but for its position about an Earth day to the predawn side of the onrushing day/night terminator.
"Houston," reported Tricky Carlisle, "the Resolute has landed." He covered the mike with his hand. "Resolutely, I may add."
Applause from Mission Control, after the unavoidable but annoying two-and-a-half second round-trip delay, almost drowned out CAPCOM's equally businesslike "Copy, and congrats." There was a short silence, into which Windy McNeilly from lunar orbit injected her own "Well done," before Houston continued. "Resolute, you're cleared for a stroll."
The few minutes it took to seal the space suits worn for the landing were interminable. Kyle was second through the single-person airlock. He found Carlisle standing on a large mat; more pads, with adhesive backs and Velcro tops, remained in the airlock. Peeling paper sheets from the adhesive, Kyle handed down several pads before climbing gingerly down the landing leg that doubled as a ladder. The crescent Earth floating above the crater wall nearly took his breath away. Carlisle gave him a friendly nudge, reminding him to clear the area. The crater floor glittered and shimmered in the earthlight. Faint crunching sounds accompanied his footsteps, transmitted through mat and boots into his suit—brittle circuits crushed by his weight. Moments later, Speedy reached the foot of the ladder.
Carlisle's voice came over a private radio channel. "One more presidential curse, Doc. Say something catchy."
Kyle, having suspected this was coming, was prepared. He switched to the mission's unencrypted main frequency. "On behalf of all humanity, we reclaim our moon." Faint green digits floating on his head's up display counted down to local sunrise. He returned to a secured band. "Now what do you say we reclaim our first acre?"
They had an aluminized plastic tarp spread across the crater with hours to spare.
Kyle stood on the lip of the crater they now called home. From a thin crescent when Resolute had landed, the Earth had waxed near to half full. An enormous cyclone threatened Japan, and a second, the Philippines. Would those storms have formed absent the alien attack? There was no way to know.
He shivered, and it had nothing to do with the menace they battled. His suit thermostat was cranked low to minimize the drain on the batteries. In the tarp's shadow it was cold enough to liquefy nitrogen. "Speedy, I'm ready to walk the back forty."
"You're on camera," she assured him.
Kyle stepped out from under the awning, the direct sunlight all the more blinding for the contrast with the light-stealing surface. A metallic mesh was embedded in the glass of his helmet's visor, like the window in a microwave-oven door. Exactly like a microwave oven . . . the openings through which he gazed were too small to admit microwaves. Downhill, like a rock garden arranged by drunks, stretched their experimental plots: dozens of regions of varying sizes, shapes, and textures. Pole-mounted videocams swept back and forth, monitoring each plot. It was ironic, Kyle thought, that they'd had to bring solar cells from Earth to power the cameras.
He made his way carefully down an intersector boundary, along what Carlisle had dubbed a carpet runner. Nails driven by rivet gun into the rocky surface held the walkway in place; an adhesived patch had been set carefully over each nail head to seal the hole. The Velcro'ed surface gripped Kyle's boots, holding him to the supposed nanomachine-free safety of the from-Earth path. It wasn't as though on a microscopic scale the adhesive didn't have gaps—they had no choice but to trust the shadows from the patches to keep the nannies underneath inert.
As on every sticky-footed excursion from the Resolute, Kyle felt cheated. He longed to move about in the kangaroo hop made famous on the Apollo missions. Status lights in his helmet reported all three microwave reradiators in his suit were operational.
"Are you done yet?" Carlisle's words, accompanied by a chuckle, were more an old joke than a status inquiry.
"Just medium rare." Humor was the only way to cope with the ever-present danger. Untreated, each square meter of the sunlit surface generated close to seven hundred watts—like the interior of a standard microwave oven at its full-power setting. He was in line of sight of many square meters. Line of sight . . . or line of fire. It was a disconcerting thought. The gauge on Kyle's wrist detected none of the microwaves that, had they been directed at him, should be immediately dispersed by any of the three reradiating systems he carried. Despite the redundancy, he yearned for a physical, foolproof, grounding cable. Alas, a trailing tether would almost certainly slide off the protective runways and onto the nanny-covered lunar surface.
Their crater was a dimple within a great flat plain, one of the lunar maria. Standing on that "sea-level" surface, he could see barely a mile in any direction, the horizon foreshortened by the moon's diminutive size. Small relative only to Earth, of course: the surface area was close to fifteen million square miles. As many stars shone overhead, diamond-brilliant and unwavering.
"Quit your sightseeing," called Carlisle.
"You caught me. Again. Starting with plot one." Bending and crouching, pacing back and forth along a runner, he examined the first plot from several angles.
Soon after landing, in the shadow of plastic sheeting temporarily stretched between poles, this slice of territory had been bulldozed clean of visible infestation by radio-controlled robots. The little RC vehicles would stay behind and be teleoperated from Earth; Las Vegas bookmakers were taking bets on how long the devices would last. Alien circuits began refilling the area as soon as the sun-blocking sheeting came down. The masers and the solar cells powering them were completely restored within minutes.
They'd "fenced" the area with shadows before the robots scraped it clean again. The field regenerated almost as quickly the second time, this time entirely from random spots within the torn-up field. It was, apparently, hard to remove every trace of nanotech "seeds" too small to see. That result reinforced the mission directive against touching the surface. They'd mechanically cleansed plot one repeatedly, and the results never changed: rapid regrowth. Repeating the experiment at scattered test spots gave comparable results. The propagation rate was always in the neighborhood of seven miles per day. "No surprises, Craig. Plot one is entirely regrown since your last inspection. No holes or gaps. I'm moving on."
The next few plots had, like plot one, been wiped clean and allowed to regrow to calibrate growth rates. There was some variation, correlated to robot-measured differences in trace-element concentrations. Plots two through ten had been treated with acids, bases, and other pollutants. No chemical made a significant difference to the regeneration rate. No coating disabled unplowed masers or solar cells for any useful length of time. For completeness—Kyle privately considered it more a matter of desperation—they were trying combinations. "We're not accomplishing a damn thing here."
"Any thoughts why?" asked Speedy.
"Sure. Nanomachines manipulate individual atoms. With such abundant solar energy, the nannies have no problem repairing themselves or cloning themselves or disassembling any inconvenient molecules created by our chemical spills. We must concurrently destroy every smaller-than-microscopic nanomachine, and keep new ones from migrating in from neighboring areas, to make any difference. The little critters are too hardy."
"That sounds a lot like admiration, Doc," said Carlisle. "By the way, no progress here, either." The commander was inspecting another stretch of plots, these heat-treated. They'd tried, among other methods, a rocket-fuel flame thrower, an electric-arc furnace, and a large, sunlight-concentrating, paraboloid mirror. It took three thousand degrees to purge a shadow-fenced area. No one could imagine a way to apply the technique on a moonwide scale.
"It is admiration, but don't worry." Kyle straightened from the crouch in which he'd been eyeing yet another plot. "Respect for their ruggedness doesn't detract from the scariness." If only there were some way to tame these beasts.
It didn't help Kyle's mood that by the time he headed back to the ship a new typhoon was forming in the Indian Ocean.
Kyle resisted the inane urge to wave at the fast-moving glimmer that was Endeavor. "How's the R&R, Windy?"
The pilot mocked retching. "It's no holiday when all the food is reconstituted."
The meals down here were squeezed from tubes. There hadn't been weight margin or physical space in the lander for a fancy, shuttle-style galley. Of course, Windy would trade places with him in an instant. "How's our farm looking from up there?"
"Huh. I thought the idea was to not grow stuff."
"Ahem?"
"Lessee." There was the unmistakable flipping of paper in a clipboard. "Okay, these are my notes. I'll downlink the details in a minute. For fields one through eighteen and twenty through thirty-six, the emissions as always correlate nicely with the size of the plot and the regrowth rate you're reporting from the ground."
"And nineteen?" Kyle didn't let himself get excited. Most anomalies were data-collection glitches.
"This is interesting. Right after our noble commander last flame-broiled nineteen, not only did nineteen turn off, but I noticed that a whole region around that plot stopped emitting."
That was interesting. "And did that larger area come back on when plot nineteen did?"
"Roger, Doc." There was more rustling of paper. "And guess what: plot nineteen is smack in the middle of the larger blanked-out region. What do you suppose it means?"
"I am without clue." With a fat gloved finger, Kyle poked at the keypad on his suit's left sleeve. His head's up display showed that three of their little robotic tractors were idle. "Windy, how much longer are you in range?"
"Directly? Three minutes plus. But one or more of the satellites we deployed always has Resolute in line of sight."
He should have remembered that. The eighteen-hour days were taking a toll. Best to confirm his thinking. "Beside comm, they detect microwaves, too? Show if an area is on or off?"
"They have to be pretty much right above to spot beamed microwaves, but then, yes."
The planet overhead had passed full and was waning. In a few Earth days, lunar night would fall and they would pack up and rendezvous with Endeavor for the trip home. There could be no more unique clock, nor a better reminder of why they were here.
How much longer did they have to save the Earth? Climatologists, when pressed, threw up their hands. Before The Big Dim, they had invested years, even decades, on competing models of global warming—simulations envisioning nothing remotely like recent conditions. The not-for-attribution best guesses were that temperatures would creep up and up until upper-atmosphere vapor levels crossed a much debated threshold . . . followed by runaway greenhouse effect. After that, planetary temperature would skyrocket.
Can you say Venus?
His exhausted mind had wandered again. "Trickster? Speedy? Were you listening?" Both responded in the affirmative. "I'd like the untasked robots to go over plot nineteen with a fine-toothed comb."
"Agreed," said the commander. "Windy, you and your flock of birds keep an eye on us."
Neither the patiently surveying robots nor their human controllers had noticed anything different about plot nineteen when, once more, it and the surrounding region went inert.
"Good morning, Resolute," called the familiar voice. "This is Carlene Milford."
"Good morning, Madam President," answered the three crew. It was morning in Washington, but here lunar nightfall was fast approaching. They were nearly packed and entirely eager to go home, even though they had left not a single bootprint on the moon's surface. The Resolute's landing stage, like the mats and runners on which they had trod, would stay behind with its certain contamination of dangerous nanotech.
"My compliments, and the world's appreciation, for your bravery and discoveries. We wish you a safe journey home."
At least, thought Kyle, the rest of the world has finally accepted reality: that the aliens had been a threat. "Madam President, are you linked into our video system?"
"Yes, Dr. Gustafson. Those are cramped quarters you've been living in."
While true, the Apollo astronauts had managed in a fraction the space. "If you can, ma'am, I suggest you switch to our camera six." Presidential calls are scheduled well ahead of time, giving Kyle ample opportunity to pre-position the videocam. One of the lander's monitors showed the recommended fisheye-lens view of the pallid surface, across which, if one looked closely, several black rectangular mats were distributed.
"You've worked with presidents, Doctor. You know how busy are our schedules. I've been briefed, of course, but I'd like to hear from you directly a short summary your findings."
The operative word, Kyle knew, being short. What on her docket was more urgent than preventing life's extinction on Earth? "Yes, ma'am. You're aware the aliens covered the moon with self-growing, self-regenerating masers, and solar cells to power the masers. These structures are tiny, on the scale of inches. We also knew there had to be, but did not at first find, components for control. There had to be sensors for locating the Earth in the lunar sky."
Viewed from the moon's surface, Earth spanned a mere two degrees of arc. Due to the tilt of the moon's axis and the ellipticity of the moon's orbit, Earth from the same lunar vantage point migrated around a celestial box of about fifteen degrees by thirteen—movement the astronomers called libration. These weren't details any politician wanted or needed. "As there has to be computing power somewhere giving very precise directions to the masers." Any single maser was a physically rigid structure, the direction of whose output was fixed. By precisely controlling the emissions of sets of masers, however, those outputs could be aggregated into vast steerable beams. It worked just like a military phased-array radar.
"Not my specialty, Doctor, but it seems logical."
Kyle fancied he heard the sound of eyes glazing. Simplify! "Our work involved altering test plots on the lunar surface. As expected, a cleared region did not radiate until the masers regrew. To our surprise, however, one experiment rendered inert an area much larger than had been temporarily cleansed. We had happened upon a sensor that gave steering guidance. When that sensor could no longer spot Earth, the masers that it controlled stopped firing." Emissions from a blinded region would likely interfere with an adjacent well-aimed beam; suppressing an area whose sensor was for any reason targetless made sense.
"It sounds like we finally got lucky," said the President.
Now that the explorers could recognize the sensors, they knew how widely those sensors were dispersed. They had actually been unlucky, considering how much landscape had been tested, to go as long as they had before randomly encountering a sensor. "We've been using our utility robots to blind sensors with opaque scraps." While nanotech quickly regrew a destroyed sensor, an intact sensor could be covered. The nannies didn't distinguish shadow from nightfall.
"And the robots can spot sensors?"
If only it were that easy. "You might have heard of archeologists hunting for lost cities with space-based, ground-penetrating radar. Major McNeilly"—he caught himself before calling her Windy—"used Endeavor's radar to map beneath her orbit. A subsurface view, and only using a narrow range of frequencies, reveals a nonobvious large-scale structure. The alien infestation repeats on the scale of a square kilometer. There's a sensor at the center of each region.
"This is what we do. Using the radar survey, we guide a robot to the center of a region. As the robot trolls back and forth, we use its videocam to hunt for a small and subtle discontinuity in the artificial surface: the sensor. The robot then parks atop a suspected sensor until a satellite passing overhead can confirm that the surrounding area has stopped emitting. The robot sets a scrap of asbestos over the confirmed sensor, then heads off to the next region." At a snail's pace.
"It sounds ingenious, Doctor. Is it too soon to say our problem is solved?"
He suppressed an oath. The moon was big. "I'm afraid, ma'am, that it is too soon. Disabling all the masers this way will take an armada of moon-orbiting satellites and myriads of moon-crawling robots. There are millions of sensors to be blinded, one by one." And, perhaps, again and again. Kyle expected the nanotech to eventually, atom by atom, carry away the obscuring mats—as they had, on the day of The Big Dim, removed the last thin skin of lunar dust that had disguised the spreading infestation.
"It sounds like an epic undertaking, Dr. Gustafson, but nonetheless something we can undertake. We have far greater cause for hope than before this expedition. I look forward to discussing it with you, and to meeting with the whole crew, very soon."
The President did not articulate the thought in everyone's mind. The four astronauts were returning to a remote quarantine, their exit from which was far from certain.