Sortie
(1994)*
Hal Clement

	His Aitoff screen was offering one of its occasional, brief, random, views of Sergeant Gene Belvew's real surroundings, cutting him off for half a second from those of Oceanus deep in Titan's atmosphere, when the pipe stall occurred.

	It would, he reflected at one level of his mind. He didn't believe in an unqualified Murphy's Law, which was strictly for civilians, but a scientist of any rank understood Murphy' s Law of Selective Observation. If the jets had chosen any other time, he would have known it was coming, forestalled it easily without real thought, and forgotten it promptly as unimportant. As it was, his first warning was the waldo suit's use of nonvisual input. It administered a sharp chill almost simultaneously in both of his elbows. By the time he could see Titan again, half a second later, thrust was gone and accelerometers showed that Oceanus was being slowed sharply by the dense atmosphere. His reflexes had already operated, of course, just a trifle later than they would have from a visual stimulus. The aircraft had practically no reaction mass in its tanks; he had been trying to replenish that at the time. The big satellite's gravity, which his body in orbit couldn't feel any more than it could the deceleration, was feeble; if the craft slowed too much now, even the vertical dive he was entering wouldn't get him back to ram speed from his present altitude. Diving into the surface would not hurt him physically—the waldo's feedback didn't go that far—but would still be a bad tactical mistake. Ramjets could not be picked from trees, even if there had been trees this far from the sun. For increasingly scary moments the tension mounted as his elbows stayed cold; then ramflow resumed simultaneously in both pipes and the speed of his dive abruptly began rising with the restored thrust. Still reflexively he pulled out into horizontal flight with over a hundred meters to spare, put his nose—his own, not the ramjet's—in the face cup and moved his head slightly to run the Aitoff screen through its half dozen most-likely-useful vision frequencies. He was already pretty sure what had caused the stall, but pilot's common sense agreed with basic scientific procedure in demanding that he check.

	Yes, he was still in the updraft; the screen displayed the appropriate false-color all around him, and the waldo—which doubled as an environment suit, and therefore did not interfere with his breathing system—was reporting the excess methane as a salty taste. As usual, there had been no one but himself to blame. He'd been driving just a little too slowly, trying to see below while filling the mass tanks, and a perfectly ordinary but random and quite unpredictable drop in the density of the rising current had raised the impact speed needed by the jets. If there'd been nothing backing up the interrupted visual sensors he'd have learned too late and had over a hundred meters less leeway.

	No point thinking about that.

	"What happened, Sarge? Or shouldn't I ask?" Barn Inger, Belvew's co-ranker and watch partner, didn't bother to identify himself; only a few dozen people were anywhere near Saturn, and everyone knew the voice of everyone else who mattered. As Belvew's "buddy" one of his jobs was to check with Gene vocally or in any other way possible whenever something unexpected occurred; the "shouldn't I ask" was a standard courtesy. Not everyone enjoyed admitting mistakes, however important they might be as data, and the terminally ill people who formed an even larger fraction of the Titan exploration crew than of Earth's remaining population were often touchy.

	"I rode too close to stall. It's all right now," Belvew answered.

	"Use anything from the tanks?"

	"Nothing to use. There was enough room to dive-start." Belvew did not mention just how little spare altitude he had had and Inger didn't ask.

	"You're still over Carver, aren't you? You could have put down and tanked up from the lake." This was quite true, but neither speaker mentioned why the pilot had dodged that option without conscious thought. Both knew perfectly well; Inger's stress on the "could" had been as close to being specific about it as either cared to go. He changed to a neutral subject.

	"You seem to have the fourth leg about done." Belvew made no answer for a moment; he was spiralling upward to start another pass through the raindrop-rich updraft—at a safer altitude this time. He wanted mass in his tanks as soon as possible, but was now prepared to accept the lower concentration to be found higher up. In standard light frequencies his target was indistinguishable from an Earthly thunderhead—there was even lightning, in spite of the nonpolar nature of the droplets, and Belvew faced the task of making several passes through it fast enough to avoid another ram stall but slow enough to escape turbulence damage to his airframe.

	"Just about," he answered at last. "I still have enough cans to finish Four and most of Five. I hope all the ones I've dropped so far work. I'd hate to have to go back just to make replacements. There's too much else to do." He fell silent again as the waldo began pressing his body at various points indicating that Oceanus was entering turbulence. His fingers, shoulders, knees, and toes exerted delicate pressure—now this way, now that—on the suit's lining, answering the thumps he could feel and forestalling the ones the Aitoff screen was letting him anticipate by sight. For nearly two minutes the aircraft jounced its way through the vertical currents, and as the turbulence eased off and the air around his viewers cleared the pilot gave a happy grunt. He would have nodded his head in satisfaction, but that would have operated too many inappropriate controls.

	"A respectable bite. Nine or ten more runs at this height should give me takeoff or orbit mass."

	"Or several dozen stall recoveries," his official buddy couldn't help adding. Belvew let the remark lie, and two or three minutes passed before anyone else spoke. The rest of the team had their own instruments and could read for themselves the rise of tank levels as the jet's collection scoop gulped Titanian air, centrifuged the hydrocarbon fog droplets out of it, stored the liquid, and returned the nearly pure nitrogen to the atmosphere.

	"There's another odd surface patch a few kilos west of Carver," Maria Collos' voice came at length, as the main tanks neared the seven tenths mark. "It wouldn't take you very far off plan to look at it before you start Leg Five."

	"Like the earlier ones, or something really new?" asked Belvew.

	"Can't tell for sure in long waves. It could be just another bit of melted tar. Even if that's all, we're getting enough of those to need explanation."

	"One would need explanation!" snapped Arthur Goodell, the least patient of the group usually, and excusably because of the endless pain of Synapse Amplification Syndrome. "I can see—so can you—how tars would settle out of the air as dust at this temperature. I can see dust getting piled into dunes even in the three kilo currents that pass for gales here. I can see it looking like obsidian if it gets melted and cooled again. What I don't see is what on this iceball could ever melt it."

	"I've suggested methane rain, dissolving rather than melting the surface of a dune as it soaks in and forming a crust as it evaporates," came the much milder and thinner voice of leukemia case Ginger Xalco.

	"And I've suggested landing and finding out first hand whether those nice, smooth, glassy hilltops are the thin shells of evaporite over a dune, as you're implying, or the tops of magma lenses," snapped Goodell. "When do we do that? You've plenty in your tanks now. Gene. Why not take a good look at this new one—whether it turns out to be just another for Maria's list or something really different? And don't tell me it's against policy; we're here to find things out, and you know it. To quote the poetic character who wrote our original mission plan, 'there's no telling in advance which piece of a jigsaw puzzle will prove to be the key to the picture.' "

	"It's not a matter of set policy," Belvew replied as mildly as he could—he had his own troubles, even if they didn't include SAS. "Avoiding risk to the jets before the surface and weather gear are all deployed is common sense, and you know it. Once they're in action, long term studies can go on even if we lose transport. We've made one landing to deploy the factory, and a couple of others to restock from it, after all."

	"I know. Sorry." Goodell didn't sound very sorry, actually, but courtesy had very high priority. "It'd be nice to be around when some of the results crystallize, though. And you can't count the later landings because they were in the same place and we knew what to expect."

	"Not exactly. The original shelf was gone."

	"The area was plain Titanian dirt, with no cliff to fall down this time. Even I could probably have set down safely." No one contradicted this blatant exaggeration. "The old saw about dead heroes—"

	"Doesn't apply, Arthur." Maria, somehow, was the only one of the group who could manage to interrupt people without sounding rude. "We're already heroes. We've been told so." There might or might not have been sarcasm in her tone. No one else, even Goodell, spoke for a moment. Then Belvew referred back to the landing question.

	"There's no reason I shouldn't make a ground check after finishing the Leg Four, if Maria's radar and my own eyesight can find me a landing and takeoff site. Actually, we're all as curious as Art about the smooth stuff, and it's good tactics to eliminate possibilities as early as we can. Let me top off these tanks just to play safe, and then you can put me back where I left Leg Four, Maria. After that's done I'll scout your new patch for landing risk."

	No one commented, much less objected, and Gene made his remaining passes through the thunderhead with no actual stalls. There were no remarks about his two close calls, either; everyone had flown the ramjets at one time or another except Goodell, whose own senses were drowned in pain too much of the time to let him use a body waldo, and Pete Martucci, whose reflexes, though he was the only one of the dozen not known to be dying of something, had never been good enough for piloting. All knew the ordinary problems of flying.

	"Standard turn left four five point five," Maria said without waiting for Belvew to report that his tanks were full.

	"Left four five point five," he acknowledged, banking promptly to seventy-four degrees. The group had established a half-Earth gravity as a "standard" coordinated turn on Titan. The ramjet's wings, stubby as they were, could still give that much lift at ram speed below ten kilometers or so altitude. He snapped out of the turn in just over sixteen seconds, since mission speed was an equally standard one hundred meters per second when nothing else was demanded by circumstance.

	"Your heading is good. You'll reach the break in Leg Four in two hundred fifteen seconds from—NOW! Nose down so as to reach three hundred meters at that time. I've allowed for the speed increase at your present power setting, so don't change it. On my time call, level off and do a standard right turn of one seventy seven point three. Start dropping cans at standard intervals ten seconds after you finish the turn. The leg ends at the twenty-second can."

	"Got it." Belvew remembered again, with the aid of the blunt needle mounted in the suit under his chin, not to nod. There were no more words until the time call, and no more after it until the last of the pencil shaped and sized "cans"—containers for seismometers, thermometers, ultramagnetomers, and other gear—needed for the fourth leg of the planned seismic network had been ejected.

	"Okay, Maria, take my hand." Belvew nosed the jet upward as he spoke. All the others were listening and watching as their particular instruments allowed except Goodell, who was meticulously testing the output of each of the recently dropped cans. None interrupted the terse directions which formed the response to the pilot's request, and he hurtled northward along the eastern shore of Lake Carver eight hundred meters above its surface with his earphones still silent. He knew they could follow his progress on their duplicates of his own Aitoff, and that he could expect to have his attention called to anything he seemed to be missing, so he concentrated on the screen area a third of the way from center to lower margin. This covered the region he would pass over in the next few seconds. It was only slightly distorted by the projection which let a single screen squeeze the full sphere into an ordinary human field of vision, though this mattered little; everyone had learned long ago to correct in their own minds even for the extreme warping at the edges. No part of the aircraft itself showed; though some of the two dozen cameras mounted in various parts of its skin did have wing, nose, or tail in their fields, the computer which blended their images on the single full-sphere display deleted these.

	Unfortunately.

	The liquid surface was currently glass-smooth ahead and left of the jet, though even Titanian winds could raise waves; gravity was weak and liquid density low, and the highest winds occurred over the lakes themselves where evaporation lowered the air density far more than temperature changes could. Belvew gave the lake only an occasional glance, keeping his main attention on the land ahead where the patch to be examined should be.

	"Three minutes," came Maria's quiet voice. The others remained silent. "Two. You might be able to see it now." The pilot scanned through his vision frequencies again, dodging the longer wave lengths which were more strongly absorbed by methane.

	"I can, I think. Forget timing. I'm slowing to ten meters above stall—no, make that twenty for the first run—and going down to a hundred meters, and I'm cutting out the random reality reminder. If I lose track too seriously with where I really am we can cut my shift short later. I'll recover. The air looks steady, but I don't want another stall at this height."

	No one objected aloud, though there must have been mental reservations. Belvew was the pilot for now; it was up to him to weigh relative risks to the aircraft. Negative comments would have been distracting, and therefore dangerous as well as discourteous.

	The smooth patch grew clearer as the seconds passed. It was larger than most, about half a kilometer across, roughly circular but with four or five extensions reaching out another hundred or hundred and fifty meters at irregular points around its circumference. It might have been an oversized amoeba as far as outline went. The color seemed to be basically black, though it reflected the pale reddish-orange of the Titianian high smog as though from glass.

	No small details could be made out from the present altitude and speed. Gene banked to a much less than standard turn rate for this speed, swung in a wide, slow circle north of the patch, and made a second pass in the opposite direction. This time the reflection of the brighter section of southern sky where the sun was hiding could be made out; the surface looked more than ever like glass, as Maria had described the others on her map, but there were still no informative details.

	He made two more runs, this time at thirty meters above the highest point of the patch and only two meters per second above ramstall, tense and ready to shift to rocket mode—to cap the intakes and send liquid and extra heat into the pipes at the slightest drop in thrust. He was not worried about the wings stalling; even those stubby structures had plenty of lift area in this atmosphere and gravity, and the jet had been designed so that they would go out at higher airspeed than any control surfaces.

	Nevertheless, his attention was enough on his aircraft and far enough from the ground so that it was Barn who spotted the irregularity.

	"There's a hollow about ten meters across half way from the high point to the base of that northwest arm. It did funny things to the jet's reflection as we passed this time, but I can't see it now. I can't decide exactly how deep it is, but it's just a dent, not a real hole."

	"Did anyone else spot it?" asked Belvew. Most of them had, but none could give any better description. The pilot made another pass, this time devoting a dangerous amount of his attention to the surface below, and saw the feature for himself; but he could make out no more details than the others.

	"You know we're going to have to land sometime," Goodell said in what was meant to be a thoughtful tone.

	"I know." Belvew was thinking too. There was half a minute's pause before the remote-lab manager tried again. 

	"What time is better than now?" The pilot could answer that one.

	"When we know more about the strength of that surface. If it's just a crust, as the rain theory suggests, Oceanus could break through and smother the jet scoops in dust, or mud, or dirt, or whatever form the stuff under it happens to have."

	"You have plenty of cans. See what happens when one of them hits. You needn't use its chute; let it hit as hard as Titan can make it."

	"Good idea." The pilot, with much relief, cautiously raised his speed to standard—too sudden a boost to the flame could make the pipe frontfire—and climbed to a full kilometer. There was still no wind, but the patch was a harder target than he had anticipated. Without its parachute the slender container took much longer to lose the jet's speed, as all had expected but none could estimate quantitatively. The first attempt overshot badly. Belvew couldn't see it, but Inger and Collos followed it with other instruments until it buried itself beyond detection in ordinary, firm Titanian "soil" a hundred and fifty meters beyond the edge of the glassy patch.

	The second try, with Barn calling the release moment, was much better and quite informative in its way. The can's own instruments stopped radiating at the instant of impact, ending passive measurements, but Maria's shortest viewing waves showed that the little machine, solid as it was, had shattered on contact. The surface seemed pretty strong. Belvew was less happy than he might have been; if the can had broken through undamaged it would have implied a crust too weak to take the jet's weight, much less the impact of a poor landing just here and now.

	As it was, the next test appeared to be up to him. He thought furiously. Would anything except an actual landing tell them what they needed to know?

	The jet lacked landing gear in any ordinary sense; there were no wheels, floats, or real skids. Its belly was shaped into a double keel meant to give it catamaran stability in an attempted liquid landing and broad support on dubiously solid surfaces, though once stopped the body would sink to something like three quarters of its diameter in the best-guess mixture of Titan's lakes. It would float a little deeper in pure methane. This was why no one wanted to make the first lake landing; it had not occurred to anyone until much too late even to calculate, much less test, the results of attempting a rocket mode start with the pipes totally immersed in liquid. The log of the Earth to Saturn orbit had several similar annoyed entries.

	The keels were adequate landing skids on a solid surface; one could make a pass at just above wing stalling speed, grazing the apparently smooth hump. If he did it right, he might resolve the question of whether the patch was solid or crust. If the latter, of course, there would be no certainty about its ultimate strength until the jet came to a stop and the wings lost all their lift.

	The convexity of the surface complicated the problem slightly. If he hit too hard, easy to do on the upslope side, the question of whether the crust was stronger than the jet's belly and keels would also become relevant.

	The initial landing, Earth days before, had been on a smooth shelf of ice near the foot of the steep side of what looked like a tilted block mountain; Titan seemed still active tectonically. There had been no trouble anticipated in detail, though of course the pilot—Inger, at that time—had kept alert for the unforeseen. This was fortunate, since the exhausts had started a thermal-shock crack in the ice which chased the jet for most of its landing slide. The pilot had just managed to avoid riding to the foot of the hill on several million tons of detached shelf by a final, quick shot of thrust. The three hours it had taken for the factory pod to climb to the bottom, get to a safe distance from the cliff face and the new pile of ice rubble, put down roots and start growing had been spent in a high state of tension. Not just by Inger.

	When it seemed certain that no more pods would have to be sent out, the fact that only a short length of ice shelf remained for takeoff had to be faced. Inger had been forced to use more than normal thrust, and while he concentrated his attention straight ahead, the rest of the group watched another crack chase him along the shelf, and more ice rubble fall, bounce, and roll toward the new factory. There was no longer any ice platform to land on when he did get into the air. The two later descents to pick up cans, once the factory had matured, had been on "ordinary" ground and proved uneventful. The drag on the skids, which all had feared might stress the aircraft too highly—this was why the ice shelf had been chosen for the first touchdown—had been sharp but not dangerous, and the subsequent takeoffs had presented no problems except a rather larger demand for reaction mass than had been hoped.

	Belvew remembered the ice landing vividly as he planned his present one. Some dangers were more foreseeable this time, but there was the chance that concentrating on these might lessen his readiness to respond to something unforeseen as promptly as his friend had done.

	Well, Theia and Crius were still available at the orbiting station, and the chance had to be taken sometime. No one would blame him for losing Oceanus.

	At least, not aloud.

	He called for a wind check—even a few kilometers an hour could make a difference—and held a constant heading for ten kilometers while Inger adjusted a superimposed grid on his own screen's image. Eventually the moving ground features followed one of the lines and let him tie their apparent motion.

	"Only one point seven, from eighty seven," was the verdict. Belvew swept out over the lake without asking Maria for a heading, lined up with the patch from a dozen kilometers to the west, and eased back on his power. He nosed up enough to split the result between descent and speed loss, and reached the shore fifty meters above the liquid and a scant two meters a second above ram stall. Chewing his lower lip, which fortunately affected no waldo controls, he closed the ram intakes and fed the liquid to the plasma arcs. There was a grunt of admiration which might have come from Goodell; the shift to rocket mode was almost perfectly smooth. The longitudinal accelerometer swung promptly to a negative reading, and stayed there as Belvew turned down his fires even more. He was approaching wing stall now, and began increasing the camber of his lifting surfaces toward the barrel-section shape which had been used so few times before, and never by him. He should, he suddenly realized, have done a few practice stalls two or three kilometers higher. He convinced himself quickly that breaking off the approach and going up to do this now was not really necessary but didn't ask for anyone else's opinion.

	The rippled dust was fifty meters down—forty—thirty ...

	The glassy convexity loomed ahead, rising to meet his keels. He nosed up even more, killing descent briefly while airspeed continued to drop. The bulge kept rising toward him. Without orders, Inger began calling speed. The wings should maintain lift down to sixteen meters per second, Belvew knew, and the stall then should be smooth. Some levels of theory were pretty solidly established.

	"Twenty-two zero—twenty-one nine—twenty-one eight ..."

	The keels were two meters from the bulge, and he nosed up still farther to keep them so as the airspeed continued to fall. That wouldn't work much farther; past the top of the dome he'd have to drop the nose to make contact before stall, and that would speed him up. Not much in Titan's gravity, but any would complicate the maneuver.

	The side edges of his screen, representing the view to the rear, darkened suddenly, but he kept his attention ahead. If there was anything really important aft, someone would tell him, though he hoped they wouldn't before he was stopped. For an instant he wished he were actually riding the jet, so that he could feel when touchdown occurred.

	But he knew anyway. The accelerometer and three human voices supplied the knowledge simultaneously. He stopped reaction mass flow and quenched the plasma fires almost completely, but kept ready to use fractional rocket power on one side or the other if a swerve developed. Any yawing could roll the Oceanus onto its back, and it seemed most unlikely that whichever wing was underneath could take such treatment.

	"You're down!" came Ginger's voice, this time separate from the others. Belvew snorted faintly, and spared enough of his attention to utter a bit of doggerel which had survived in various forms from the time of fabric-covered aircraft.

	"A basic rule of fliers, and all who've ever hopped: a ship is never landed until it's really stopped."

	But deceleration was now rapid as the keel friction made itself felt, and a quarter minute later the landing was complete. Belvew knew he wouldn't feel it, but his stomach tightened up anyway for several more seconds as he watched screen and vertical motion meters for evidence that the ship was breaking through a crust.

	Apparently it wasn't, and at last he felt free to let his attention focus on the view aft.

	The screen darkening was from a slowly spreading cloud of black smoke, its nearest edge well over a hundred meters astern. It could not, the pilot saw at once, have been produced by friction between his keels and the surface; his landing slide hadn't started that far back, and his thermometers showed that the keels were at about a hundred and fifty kelvins. They were cooling, but not so rapidly as to suggest they had been hot enough to boil Titanian tar in the last few seconds.

	Not that anyone really knew what temperature that would take, he reflected fleetingly.

	More to the point, a fairly deep trough in the surface, starting just below the near side of the smoke cloud and extending as far back along his approach path as he could see, confirmed that whatever had happened to the surface had come before touchdown. The most obvious cause was the exhaust from his pipes.

	The smoke was being borne very slowly away from him by the negligible wind. The trough, perhaps half a meter deep and ten or twelve wide, remained uniform as the receding cloud revealed more and more of it, extending down the slope of the convexity. The jet had come to rest almost exactly at the top of the bulge, it seemed; both pitch and roll axes read within a degree or so of horizontal.

	"If it's a crust, it's pretty thick," Goodell remarked.

	"Unless the jets melted their way down and just produced more of it," rejoined Ginger.

	"Could be." Being human, Goodell liked his own idea better; being a scientist of rank, he knew that alternative hypotheses, however unlikely, should always be developed as early as possible in hope of maintaining objectivity. "Let's get samples."

	Belvew had powered down the flight controls, except for those which might be needed for emergency takeoff, and could safely nod his head, not that anyone could see him from their quarantine compartments.

	"All right, in a few minutes. Non-destructive examination first. I assume everything in sight's been recorded; now let's look."

	"Right." Goodell's voice was a fraction of a syllable ahead of the others. Belvew activated the short-focus viewers on the lower part of his fuselage, and allowed their images to take over the Aitoff screen as his friends above chose—no, not above, he reminded himself; he was above with them; another real-surroundings reminder must be due. No one, however, said anything for several minutes; the surface still resembled obsidian at every magnification available and at every point the viewers could reach. The depression seen from the air was now hidden by the curve of the hill ahead, even though they were looking from its top, and the nearest point of the track presumably made by the exhaust was too distant for a really good look.

	"I guess we dig," Pete said at last. Belvew nodded again, as uselessly as before, but operated more of his controls.

	The object which dropped from between the keels might almost have been an egg-shaped piece of the surface itself, as far as texture went, about fifty centimeters in its longest dimension. Until it reached the ground, which took an annoyingly long two seconds or so in Titan's gravity, it appeared totally featureless. When it did strike, it flattened on the bottom to keep from rolling, uncovered a variety of optical sensors on the top and sides, and extended handling and digging apparatus, coring tools, and locomotion equipment.

	Structurally and functionally, it straddled the accepted arbitrary borderline between nanotech equipment and pseudolife; it had been grown like the cans, not manufactured, and much of its internal equipment was of molecular size.

	"Take it, Art. Where to?"

	"Aft, I'd say. I'll sample at each meter until we reach the exhaust trail, and then really dig. The smellers report ready."

	The "smellers" were of course the analytical equipment, and everyone began to tense up again as the egg crawled to its first sampling point and scraped up a specimen.

	"How hard?" queried several voices at once,

	"About three. If it's a crust, it must be pretty thick to take Oceanus' weight."

	"Composition?" This answer was slower in coming, naturally, but overall percentages were ready in less than a minute.

	"Carbon fifteen point seven one; nitrogen eighteen point eight eight; hydrogen four point one one; oxygen twenty-eight point two five; phosphorus—"

	"Phosphorus?" Again, several voices merged. The first three species had all been observed in samples of the atmospheric smog, and there was nothing surprising about the oxygen, since water ice had been seen; but this was the first element past the second period to be detected on Titan. It was also something more hoped than expected. Study of prehistoric substances had high mission priority, but no one had been sure there would be anything of the sort to study; and even the now pretty certain tectonic activity might not bring material from very deep in the satellite. That would depend on the still unknown cause of the activity.

	Regardless of the fact that only two thirds of the sample mass had been accounted for, Ginger Xalco called out emphatically, "Structure, for goodness' sake."

	No one suggested that the elemental analysis be finished first, certainly not Goodell, who might have pulled rank if he had chosen, but who shared her feelings. He set appropriate internal machinery to work while the lab crawled on to its next sample site, and its next, and its next.

	"It's a gel, really," he said at last. "The solvent—pardon me, dispersing agent—is methanol. Most of the rest of the material seems to be polymers of one sort or another. Some of it's carbohydrate, a lot has nitrogen, but it's going to take a while to find whether we're dealing with what we'd consider proteins—polypeptides made of the same amino acids we are." 

	"Left or right?" asked Collos and Martucci together. 

	"You'll have to wait even longer for that—" 

	"Wait a minute!" Inger cut in. "Even at this temperature and gravity a gel has no business holding up a jet for very long. Gene back to outside coverage! Quick!"

	Belvew didn't need to ask what his partner had in mind; he flicked his Aitoff back to the outside scene instantly. For a moment he felt relief, and then took a second look at his keels. Without word, warning, or delay he fed energy and mass to the plasma arcs and watched the main accelerometer, wishing once again that he could feel the jet's response directly.

	For a moment the meter stayed at zero; the surface seemed to be clinging to the keels, which had sunk into it for several centimeters, and Belvew slowly increased the thrust. Then the landscape suddenly jerked backward, and a moment later Oceanus was airborne.

	Goodell gave an indignant cry as his lab, caught by the exhaust, stopped sending data. The pilot paid no attention for the moment, as he concentrated on reaching ram speed as quickly as possible while using a minimum of mass; it was Inger who answered the complaint.

	"Sorry, Art. We can grow more labs, but not more jets. Did anything else come in before we blew your machine away?"

	"No. And we don't have the sample, either." Inger pondered for a moment, then suggested, "Maybe we can find it. The lab should have held up; the exhaust cools pretty quickly, and we'd have been getting the data by beam to the plane. That would have been thrown off line. Order it to broadcast, and Gene can make some low passes back along the track; maybe we can get its signals."

	"What if it reached the lake? It must have been blown that way."

	"So much the better. We could use a reading on the composition of that juice. If anything is certain, it's that it's different from what we take from the clouds. Look at the bright side, Art."

	The answer was a grunt which might have meant anything. Barn's instruments, however, showed that Goodell had indeed sent the "Broadcast" command to the lab; whether he was waiting more eagerly for resumption of data flow or for a chance to go on complaining was anyone's guess.

	Gene had been listening, even with his attention on piloting. In spite of his sympathy for Goodell's feelings, he went up to a little over one kilometer, steered out over the lake to find a cumulus cloud and replaced the reaction mass he had just used. Then he increased thrust and nosed down—he was actually as impatient as any of the others, and more optimistic than most of them—and headed back toward shore and former landing site. He was down to fifty meters by the time the glassy patch showed ahead.

	He cut back thrust and allowed the jet to slow to ramstall-plus-twenty, and made four passes over the area at that speed, first following and then paralleling the line of the earlier landing and takeoff.

	No signals registered. With a grim expression which no one could see, and some muttered remarks which he took care no one could hear, he reset the camber, closed the ramjet intakes, and went back to rocket mode; but two more passes at a bare fifteen meters altitude and just above wing stall—neither Goodell or anyone else was going to say he hadn't tried, whatever they might think of his flying judgement—still produced no signals. The lab had either been wrecked, though that still seemed rather unlikely, or was too deep in the lake for its signals to be picked up. The presumably nonpolar liquid shouldn't interfere greatly with radio waves, but in broadcast mode any great depth certainly would. Titan was a strange place, but the inverse square law still applied. There was no basis yet even for guesses at the depths of the liquid bodies; that item had a very low priority in the program, though it would come eventually.

	"Sorry, Art," Belvew said at last as he increased thrust, returned to ramjet mode when speed sufficed, and began to climb away from the area. "I had hopes too, but I guess we've lost it. Have you any ideas what could produce a gel here?"

	"I have enough trouble guessing what could produce methanol."

	"Why?" retorted Belvew. "The makings are all there. Ice and methane could do it directly, with release of hydrogen. Maybe some of the pre-life catalysts you're hoping we'd find are actually here, if you think the reaction would go too slowly at ninety K's."

	"Naughty, naughty!" cut in Maria. "Catalysts wouldn't help. That's endothermic to the tune of over a hundred kilojoules." For a moment Gene felt an impulse to kick himself. He knew the woman hadn't had that datum in her head, but he, too, could have called it up before making himself sound silly. Then he saw a way out.

	"The energy could come from local heat," he said, trying to keep smugness out of his voice.

	"At ninety kelvins?"

	"Sure. I did mention the other product. Hydrogen would leave the scene, so no back reaction—"

	"That would happen only if it could leave the scene." Goodell had pounced on the hypothesis, and was enjoying himself. "That would be at or very near the surface, not deep underground—"

	"Or in or just under a lake," Ginger cut in. "We'll have to look for bubbles."

	"And lower than ordinary temperatures," Belvew finished. "All right, we'll look. Do some planning, you types with imaginations. I'm going to hit Line Five. Give me direction and time, Maria."

	The fifth planned seismic array was a quarter of the way around Titan from Lake Carver, ten or eleven hours flight at standard jet speed and over two even at full thrust in the thinner air tens of kilometers up. Belvew set everything on automatic, turned his watch over to Maria, and decided to eat and sleep. He needed the rest. A healthy twenty-five-year-old might have gone through the last hour casually, but he belonged to neither category. There were few now on Earth who did. Evolution of disease organisms had gotten farther and farther ahead of medical research: several dozen, counting new variations of older ailments such as leukemia, were now on the list of major health problems. Four of these involved sterility, three of them in women. Earth's human population had actually halved in the last four decades, and the average age was barely twenty years in spite of, or because of, the species' usual reaction to any major threat.

	Suggested explanations among the panicked survivors were legion; satisfactory ones nonexistent. Even supernaturalists had had to fall back on Noachian-flood-type divine wrath at general materialism rather than specific sins. The scientists had done better, but not very much; each virus and other causal organism had been identified beyond reasonable doubt, but the information had not yet produced much effective treatment. There were two favored notions—they showed little sign of graduation to theories—among scientists about the basic cause of the trend: the organisms had been tailored by people with unspecified, but presumably insane by most standards, motives; or the sudden appearance of so many almost at once was merely a statistical event like a baseball batting slump or winning streak.

	Belvew, who liked people, preferred the latter idea, but was too good a scientist to feel sure of it. CPRS, the ailment which would finish turning his own bones to something like eggshell china in another two or three years, would have taken only a little manipulation to produce from a normal human gene.

	He shifted to full automatic control, cutting out the waldo entirely, and extracted himself from the suit. It could use servicing too; he floated back to his own cell and napped while its various life support devices were recharged, cleaned, and otherwise readied for further use. The suits were not full-recycling, indefinitely lasting affairs; they had been designed foremost as waldoes. They did, of course, have fusers and life support capacity designed for Titan's environment, but could keep the wearer comfortable for only thirty hours or so there, and alive for perhaps twenty more.

	Calcium-phosphorus recrystallization syndrome also, while robbing him of energy, kept him from sleeping for very long at a time, so he was back with Oceanus well before it reached the planned site of the next seismic array. There was nothing to do but watch scenery and, of course, hypothesize on the cause of the various features. He could see the ground well enough from this height, since he could use frequencies able to pierce the small amount of smog which was below him. There were block mountains and rift valleys; there were lakes large and small. The background, as well as the covering of nearly all the more or less horizontal area, might be the hypothetical tar dust; the factory had been planted on such a surface, but at the time no analysis had been possible. Neither cans nor labs had yet been grown.

	None of the lakes was large enough to be called an ocean, as mapping from orbit had made clear enough. However, it now seemed that fully a tenth of the satellite's surface was occupied by such bodies, ranging in size from Carver, about the area of Earth's Lake Victoria, down to puddles. The Collos Patches were neither as numerous nor as large, but far from rare.

	The locations of the lakes were to some extent controlled by topography, of course; water is a unique liquid, but not in its tendency to flow downhill. Nobody, however, had yet found any order or sense in the size, location, or arrangement of the smooth patches. Belvew amused himself, as he had before, in trying to organize patterns out of those he passed over. He reached his target area without coming up with anything more meaningful than constellations.

	Maria, who had also slept, warned that it was time to decrease thrust. The jet began to slow and settle. A real-surroundings interruption occurred just after the descent started, and Belvew wondered briefly whether he should override the device. He decided against it; his tanks were full, he would be travelling high enough and fast enough to preclude any kind of stall as he sowed the cans, and vertical disturbances could be seen at a safe distance. It was only while inside them, slowed down to collecting speed, that there was any danger.

	Any known danger, he reminded himself. Any known danger except indentifying too closely with the aircraft, which the interruptions were intended to prevent. He brought his attention back to the job as Maria began issuing more specific directions.

	He had lined up on course, reached standard speed and delivery altitude, and released the first dozen of the Line Five cans when an interruption came from a voice no one had heard for weeks. It had announced then that the last of the six relay stations which kept the station in potential instant contact with all of Titan's surface was properly adjusted in orbit, and thus cleared the crew to get the actual project under way. They had mostly forgotten it since.

	"There is a change in map detail at the factory site. Please evaluate." The speaker was Status, the data handler dedicated to constant rechecking of the surface, the orbits of the station and relay units, the operation of the closed-cycle life support systems, and the current medical condition of each of the explorers. Its announcement automatically put Maria, responsible for surface mapping, in charge. As usual, the voice with which she responded was calm.

	"Gene, you're on track. You still have forty-four cans on board, which will complete about two-thirds Line Five. When they're gone, your heading back to the factory starts at three eleven. I'll get back to you with more headings for the Great Circle when you need them, or brief Status if it seems likely I'll be too busy. Barn, standard: keep an eye on Gene. Art, get any readings you can from the factory itself while I check the details Status couldn't handle. The rest of you carry on. I'll keep everyone informed." She fell silent for several minutes while she examined the surface around the factory with every frequency at her command.

	"The change," she resumed at last, "seems to be the appearance of another of our glassy patches. Its texture is identical with the others, as far as I can tell. It is almost perfectly circular, just over twenty meters across, and its center is one hundred-forty four meters from the opening of the factory's release port and directly in line with that opening—that is, directly north. Azimuth zero."

	"How long did it take to reach that size?" asked Goodell. "Can Status tell us when the last check of the site was made? And are there enough observations to tell whether it appeared all at once or grew from a center?"

	"Less than four hours, yes, and no," replied the mapper. "That's the time of the last check, and there was no sign of the patch then. Does the factory itself have any data?"

	" 'Fraid not. It's been making twenty cans and one lab an hour and paying no attention to above-ground surroundings since it ripened."

	Everyone was hearing this exchange, of course, and Belvew cut in without allowing his eyes to leave his screen.

	"Above ground? But how about below? Do any of its roots go toward the patch?"

-

	Goodell was silent for some seconds, and finally answered in a rather embarrassed and surprised tone, "I can't tell. Roots went out in all directions, of course, and I can tell pretty much what materials have been coming in through each major one, but we never thought of needing to know just which absolute direction any one root was taking."

	There must have been a spectrum of reactions to this announcement, but neither laughter nor anger was audible. The jet ejected several more cans before its pilot could think of another useful question.

	"The root which went east, toward the cliff, would be picking up water sooner or—well, sooner. The factory couldn't have started production without oxygen. Does any one of them show a richer water take than the others?" 

	"Yes. Much richer. Number 12." 

	"Then it's a reasonable guess that that one went toward the mountain, which seems to be a block of ice. Whichever is ninety degrees counterclockwise from Twelve must be pretty close to under the new patch, right?" 

	"Right. Unfortunately—"

	"Unfortunately? You mean you don't know the relative directions either?"

	"No. I don't know whether the numbers go one way or the other, or even if the numbers are in order. I labelled them as they started to pick up raw material. Sorry. Even if we'd wanted to, there was no other way to distinguish that."

	"So there goes any chance of analyzing that patch with the factory."

	"I'm afraid so."

	"So I go back and plant more labs around the factory." 

	"You drop the rest of your cans first," Maria cut in. "It won't make much difference in time. You'll be a couple of hours getting back, and it's where you'd be going anyway for more cans. There's no reason to believe there's any hurry; we don't know what causes these patches, and we can find out enough by watching this one grow if it does."

	"There could be need if the factory itself has anything to do with its appearance," Goodell pointed out. Belvew started to say something, but Maria was first.

	"We'll worry about that if it seems in order. I'll watch how fast, and which way if any special one, this thing grows. If it does. Art, keep really close tabs on the factory's behavior; that's the only other thing I can think of which might let us know of any such connection. Any other ideas?"

	"Five cans to go," Belvew answered, with no obvious relevance. "What was that return heading again?"

	Maria told him, and he finished his run in silence. He then climbed to compromise height—air thin enough for low resistance while still dense enough for the ramjets—eased in full thrust, took up the Great Circle heading back to the factory, set Oceanus on automatic control, and shifted his screen to the instruments being used by Art, Maria, and the others. There would be no verticals at this height, and he refused to worry over unknown dangers, especially when Barn was also watching. On top of everything else, as far as his own attitude went, while scientific/military procedure was of course an important and sometimes even a life-and-death matter, freedom to pay attention to a problem was equally so. The usual rank distinction between theorists and mere observers was absent here. The smooth patches might not be a military or any other kind of risk, but they now involved a basic situation change near the only equipment source currently on Titan—one which would take days at least to replace, if they did have to plant a new factory—and the more minds engaged on the problem the better.

	Barn Inger felt just the same, and he couldn't see the jet's wings either.

	It was daylight at the factory site, and would be for several more Earth days. The aircraft was on the night side, though Belvew expected to see the fuzzy, reddened blob of the sun—much of the smog was still above him—in another few minutes. Both factory and flyer were on the hemisphere away from Saturn; to see the big disc, pierced by the needle of its edge-on rings, he'd have had to shift to a real-surroundings view. Even that might not work, since the station naturally spent over a third of the time in Titan's Saturn-shadow, and usually neither he nor any of the others knew just where they were in its orbit. That was something for Status to keep track of.

	Even by day, visible light was no use for examining the factory from above the atmosphere; much longer waves were needed, and for these to have really high resolution the readings from at least a few kilometers of orbit travel had to be combined into single 'pictures' by the data processors. Maria could not, quite, watch her surface images closely in real time. By now, it had occurred to everyone in the group how nice it would have been to provide the factory with a camera, but no one mentioned this aloud. "If onlys" were against military, scientific, and medical discipline as well as common sense; all of these demanded dealing with things as they were.

	How things were was slowly becoming more apparent. Before Belvew could see the sun, Maria announced that the patch was six centimeters broader on the east-west line and eight on the north-south than it had been when first measured. Half-an-hour later both amounts had increased by another ten centimeters, and the distance from the centroid of the patch to the factory's nearest point was smaller by nearly a meter.

	"Suggests it's actually moving, not just growing more one way than the other," Bam pointed out.

	"Suggests I was wrong about its being caused by rain," was Maria's less enthusiastic comment.

	"Are you sure? Would the factory report rain?" asked Belvew.

	"No, but my viewers would. It hasn't rained there since we planted the rig. And I know rain when I see it; there's been plenty of it here and there on Titan. You ought to know, Gene."

	"I do. It's always been from verticals either over the lakes or very close to them. The general winds are so slow that a thunderstorm always dies before it can get very far from the lake that spawned it."

	"It seems to," was Goodell's more pessimistic word. "In any case, if all these things are gel like the one we started to examine, you'd have to explain how liquid methane turned into methyl alcohol."

	"There was a suggestion about that, and the factory is close to an ice source," Ginger pointed out.

	"But not to a lake," Maria admitted, still rather sadly.

	"So Gene drops another lab the second he gets there."

	"Of course," replied the pilot. "That'll still be nearly an hour, though. Aren't there a good many ready at the factory? Why not get one of those on the job—or two or three, if that'll make things faster?"

	"Pete, you're the strongest of us by a good deal. If I unseal my room, would you take the chance of a quick visit and kick me? You can hold your breath long enough."

	"No, Art," replied Martucci, "but not because I'm afraid of breaking quarantine. I'll come and stay as long as you want if it will help your lab work, but I don't see how it would."

	"Don't rub it in. I have a lab on the way, Gene." Goodell was obviously embarrassed, as the others would have been for him if they had not been equally guilty, and neither his morale slip nor the general oversight was mentioned again.

	"Better do samples on the way to the patch, not just after the lab arrives. We'll need to compare the patch with the ground in its neighborhood," pointed out Ginger. This obvious suggestion made everyone feel better; they could all share the onus of not thinking to use labs from the factory long before, and the point had been stressed that Goodell needn't deem himself the only sinner.

	The readings from the lowly travelling lab held everyone's close attention while the jet neared mountain and factory and began its letdown. Since neither Belvew nor Inger could have seen the white accumulation which started to grow on the leading edges of its wings shortly after the descent began, this made no real difference. Even when the pilot shifted full attention to his job as final approach and landing neared, neither his eyes nor his waldo sensors told him what was coming, though the accumulation was now projecting nearly three centimeters. In effect it sharpened the leading edges, but did not yet make real difference in either lift or drag. With a few hundred more flying hours experience at a wide enough variety of altitudes and speeds, Gene might have come to recognize the tiny discrepancy between thrust and airspeed. Had he actually been riding in the jet for that much time, he might even have felt it.

	And if the material had remained where it was until after he had touched down, no one might ever have known about it. There were instruments to read and report on skin temperature at many points on the machine, but not there; even with nano-and pseudo-life technology, and their effect of making complex devices almost costless to build, there were limits to how much could be installed on even a fusion powered flying machine. The heat which leaked from the pipes and was at once carried away by the airstream, so that all but the few centimeters of wing adjacent to the ramjets themselves stayed at ambient temperature, now began to creep farther out as the speed dropped to and below tens of meters per second.

	The changing camber applied by Belvew as wing stall approached may or may not have contributed to what finally happened. The operator's tiny pitch and yaw corrections as he maintained a straight and steady descent also may have contributed, or may not. A trace of turbulence in Titan's own air may even have been all that was needed.

	Whatever the cause, the sharp white rim on the front of the left wing suddenly fell or blew away from the slightly warmed surface, and the lift on that side, already more dependent on wing area than on shape, dropped. It decreased only a little, but did it suddenly, and probably not even an automatic control could have done anything useful at such low airspeed.

	The wing, short as it was, grazed the ground with its tip, and Oceanus' nose whipped down and to the left. Belvew felt a simultaneous kick from practically all his turbulence sensors. At the same instant most of the central area of his Aitoff went blank, and the mosaic of sections which should have shown the view to the rear displayed only Titan's pale peach sky.

	There was nothing useful to say for the moment, and Gene again made sure no one heard him saying it. "There couldn't have been any turbulence there!" was too much like an excuse for an adult, much less a disciplined and moderately high ranking scientist, to utter aloud. Everyone's thoughts reached the same point on the logic route, though the milestones didn't always pass in the same order.

	No ground camera views. No transport until. Seismic nets not finished. Weather tracers not even started. Labs now available only at their source, and something odd happening there.

	Humanity is a visually oriented species, and in seconds Maria was building a new image of the factory site, whose details improved moment by moment as data poured in from different directions. The factory itself was simply a square with rounded corners, a little over five meters on a side now that it had finished growing, saved from resembling a child's toy block by rain-gathering, light reading, gas ejecting and other apparatus on its roof. No one was looking at it yet, however.

	The jet's nose was crumpled back almost to the wings; the ground it had tried to displace had yielded very little. The left wing and ram pipe were hidden under the fuselage, whose tail pointed upward at about sixty degrees. The right wing and engine, also pointing upward but less sharply, seemed undamaged, but image resolution was not yet down to single centimeters.

	"So much for Oceanus. Is Theia ready?" asked Goodell finally.

	"I'll check her out," came Ginger's voice. "I think I'm nearest, and I've just slept and done my suit.

	"Are you willing to drive again, Gene?" Belvew hesitated only a moment. The crash was presumably his fault, but there was no reason to suppose that anyone else could have avoided it; and the psychology behind the custom of a pilot's flying again as soon as possible after an accident was still valid even when the pilot wasn't in the aircraft at the time.

	"Sure. I'm fresh enough. I'll nap, though, during the preflight. Call me when she's ready, will you, Ginger?"

	"Should I hurry?"

	"No!" Goodell was emphatic. "Theia hasn't been flown at all yet. Cover everything on the list, and anything else you can think of. If Maria reports some other change we may have to hurry, but not unless or until."

	"I'll be good. Gene needn't worry."

	"Who worries?" asked Belvew. He received no answer, and relaxed in his suit. It seemed unlikely that there would be time enough to get out of it for a real nap. This estimate, of course, was based on foreseeables, not human behavior.

	The station was far too massive for anyone to feel the reaction when a person pushed off from or stopped against a wall, but the departure of the jet was noticed by everyone. It was also identified, since everyone had felt it before. Reactions differed. Goodell and one or two others wondered momentarily whether they had been asleep and missed the end-of-checkout report. Peter Martucci made a wry face, as though something he had expected had happened in spite of his hopes. Gene Belvew was, for a fraction of a second, the most surprised, and of course Ginger Xalco was the least.

	But Belvew was quick on the uptake.

	"Ginger! Why?"

	"My suit's fullest, and it'll save time."

	"We don't need to save time!"

	"How do you know? I certainly don't!"

	"My suit was serviced almost as recently as yours," Belvew tacitly conceded the other argument. "It has nearly as much supplies."

	"And I use less than three quarters the food and oxygen you do. Stop being futile; I've already cut speed."

	Everyone by now understood the situation, but no one was silly enough to suggest, much less order, that the woman return with the jet. All relevant instruments showed that she had already killed enough of her station orbital speed to take the craft into atmosphere, and used most of the little reaction mass in Theia's tanks to do so. Return was not possible until she had refilled on Titan.

	Nor was there any question of taking over from the rebel even if this had been useful. Her waldo suit was in the space designed for it on the jet, and any suit there had control priority unless the wearer deliberately ceded it. "Dead-man" override from outside was not possible; such a need had not been foreseen until much too late. Construction and energy were extremely cheap, but design was not; people charged more heavily than ever for their skilled services. As a result, many structures and machines were produced with performance well short of ideal, and even the best usually turned out to lack something. The situation was not entirely new in history, but greatly aggravated by modern conditions.

	Even Goodell said nothing for general hearing. There was nothing useful to say for the moment, and what would be said later would never mention penalties, or violation of rules, or disobeying orders. Science, the search for understanding, had replaced much of the desire for personal territory, influence over others' behavior, or glory which had motivated so many of humanity's earlier high risk activities; but the need-for-knowledge culture had not evolved along quite the same lines as the religious-economic-military one. Social awareness—idealism or patriotism, though now for the whole species—was fully as great in the now vaguely militarized ranks of science, and demanded as much team effort as war, but not the same prompt and blind submission to orders which the latter had had to evolve when the opponents were other human beings rather than a universe with no personal survival urge.

	Not quite so prompt and certainly not nearly so blind, but still involving risk. Ginger knew exactly what she was doing, and why; so, in spite of his hasty question, did Gene and the others. Nothing critical was said during the hour and a half Theia took to reach atmosphere and kill her two kilometer per second relative velocity; and even when she was flying rather than orbiting, navigation instructions from Maria and flying advice from the others made up most of the conversation.

	The advice was not really needed, since Ginger had spent as much time in simulators and roughly as much actually flying Oceanus as any of the others, but somehow those still in orbit felt a need to keep meaningful conversation going—to "stay in touch."

	Xalco, after tanking up, deliberately landed at higher speed than Belvew had done, but there was no way yet to tell whether this made the difference. Theia slid to a stop half a kilometer west of the factory. She would have come closer, but there were numerous objects on the surface between cliff and factory, and some even west of the latter, which had been tentatively identified by Maria's equipment as boulders of ice from the fallen shelf. One of Goodell's labs had confirmed this; three separate specimens were nearly pure water ice, with a trace of carbonate dust. A debate on why this was not silicate had taken up much time between the discovery and the jet's landing, but no conclusions had been reached except that the news had better get to those on Earth as soon as possible. No one knows in advance which will prove the key piece of a jigsaw puzzle, but the unexpected screams for attention.

	The landing approach had not been directly over the mystery patch, but the exhaust had melted or blown a shallow trough in the regular surface and raised a cloud of smoke apparently identical to that of Belvew's earlier landing. This had not happened before, when landing had been made to pick up cans and labs from the factory. Something seemed to have changed, though admittedly the other approaches had been along different tracks. Possibly the apparently uniform area-uniform except for ice blocks and the still growing patch-differed here and there in composition. Goodell had all ripe labs now out and in action, and was sending out others as quickly as the factory completed them. Most, including Ginger, were listening to the analyses which Maria was numbering, tabulating, and locating on a map which usurped part of everyone's Aitoff, and trying to make sense out of them. Belvew was the only exception. His attention was aimed more narrowly.

	The form of the crashed Oceanus showed a few hundred meters from her sister jet, much closer to the strange patch, and he was trying to see why it had fallen. If the cause were actually turbulence there would probably be no evidence, but he still found this hard to believe.

	"Art, could you spare a lab to sample around the wreck?" he asked at length.

	"We'll get there pretty soon anyway. Any reason for special haste?"

	"Well, Ginger landed hot, but there'll be a couple of seconds after lift-off when she'll be as slow as I was. It might be worth at least a check. Maybe the ground was warmer or colder, for some reason and grew verticals."

	"How could it be?" The question, from Peter, was ignored by all but Barn.

	"We're looking for chemical action," he pointed out, "and there's methyl alcohol to explain."

	"All right," admitted Goodell. "Two labs on the way. Tell me where you want your samples, Gene."

	Belvew went back to the view provided by Theia's eyes, and strained his own looking for points of special interest on and about the wreck. It would be a few minutes before the slow-moving labs reached the spot.

	Several of Theia's cameras covered the remains, and with Ginger's consent he had first one and then another of them feed the proper spots on the screen and process their images with interferometer routines, trying to produce the clearest possible view. For some time he concentrated on the ground ploughed up by Oceanus, but could detect nothing special, and finally shifted to the jet itself. The labs had arrived and without his specific instructions were starting to collect dirt samples before he saw the interrupted white ridge along the leading edge of the uptilted right wing. Parts of it, especially toward the tip, had not been shaken off by the crash. He pointed it out to the others.

	"That shouldn't be there! How could I get wing ice here?"

	"How do you know it's ice?" asked Barn reasonably.

	"I don't, but it's where you pick up ice in Earth's atmosphere, and it had the same effect!"

	"You're blaming it for what happened?" came Maria's quiet voice.

	"Well, not yet." Jumping to conclusions was one of the cardinal sins. "Can you get a lab up there, Art?"

	"I doubt it. They weren't designed to climb a smooth surface."

	"That skin's hardly smooth anymore."

	"True. I'll try." He suited the words with action, and for over fifteen minutes sent one of his devices rolling and clawing its way along various upward-leading wrinkles in the crumpled fuselage. Each, sooner or later, narrowed enough to let the machine topple back to the ground, undamaged but ineffective. Goodell finally gave up. Belvew, less skilled but more anxious, tried from some time himself, with no better luck.

	"It looks as though some of the stuff has fallen off," Inger pointed out at last. "There should be bits of it on the ground."

	"If there are, I can't see them," replied Belvew. "I suppose we can just do lots and lots of tests all around the wreck, but how will we be sure that any offbeat result can be blamed on the white stuff?"

	"We can be quicker than that." Ginger assured them.

	"How?" asked Gene.

	"I'll show you." Several of the listeners guessed what was coming, but kept their mouths shut; there was nothing they could do about it, and objectively Xalco was being smart. She was economizing on her suit time.

	Those who failed to read the implication from her words understood a few seconds later as an environment suit with "GX" stencilled front and back entered the field of view of the jet's eyes. The walk was unsteady; even Titan's less than fourteen percent of Earth gravity was a lot more than any of the group had experienced for many months. She made good speed, however, never actually fell, and reached the wreck very quickly.

	"I don't see anything white on the ground," she said. "It either fell off further back or got buried in the dirt Oceanus ploughed up. Here, Art." She needed to jump only a short distance to bring one glove against the rime on the wing. It stuck to her suit when she tried to set it down beside the nearest lab, and she had to shake it off, leaving some liquid on her palm. All watchers tried to draw inferences while the lab unit did its work.

	"Mostly ethylene, a trace of acetylene," Goodell reported tersely after a moment.

	"Melting points?" Gene asked promptly, sure that Maria would have them on her screen at once. He was right.

	"About 104 and 192 respectively," she reported promptly. "Check you own wings, Ginger; if you picked any up after you cooled down from entry, it would still be there."

	"It is. I see it. It's lucky I landed fast, I guess. I'll wipe it off right now." Her suit disappeared intermittently, its image reappearing as odd patches and parts from time to time as she moved into and out of the view fields the computer was using for Aitoff projection.

	"Why did we pick that up these two times, and not on any of the earlier landings? And why pick it up at all, for that matter? There isn't much of either of those in the atmosphere." Gene was still puzzled.

	"I think I can guess," Barn said slowly. "You don't need much, after all; water vapor usually doesn't compose very much of Earth's air, but it freezes on wings if they're cold enough. These landings are the only ones made so far right after the jet had spent significant time up at compromise altitude, and really got its wings chilled. We can test that, if there's ever time, by going back up there for a while and doing stall exercises, at a safe altitude of course, after we get down again." He did not suggest reprogramming the Aitoff computer to show wings. None of them could have done this.

	"And until then, we make it a point to land a little hotter than we have been." Gene was relieved. "Good work, Ginger. You'd better come back up; you've used up a lot of suit time already."

	"I have plenty more. I'm going to take a close look at this patch while I'm here."

	"I don't mean to be insulting, but you're budgeting time to fill your tanks, I trust," Goodell interjected.

	"l am. But thanks for asking. Don't apologize." Her suited figure dwindled on the screens.

	"The labs can do gas analyses, can't they?" She asked suddenly.

	"Sure." 

	"Then hadn't we better look for free hydrogen? Remember the idea about the methanol production."

	"We'd need water, too," pointed out Barn. Ginger kicked at one of the boulders, almost overbalancing in the weak gravity.

	"These look like ice," she assured him.

	"They are. I checked them before," growled Goodell. "If you want a repeat—"

	"I know. That can wait. I want to see this smooth stuff." She moved a few gliding steps farther, and squatted down. A lab moved slowly toward the boulder, guided from above, but the oldster said nothing aloud. Of course this would be ice, too.

	"Give!" Came mingled voices. Ginger's suit had no camera.

	"It looks and feels through my gloves like black glass; it could still be the melted tar someone suggested. I can't scratch it with a glove claw. Labs, please."

	"Already there, as you should have noticed," answered Goodell. "Analysis so far matches the other one; it's a methanol gel, basically. I'm still working on the polymers."

	He would be. Belvew thought. Arthur, of all the group, was the most optimistic about finding prebiotic material on Titan, and the most expert on autocatalysis and similar phenomena presumably involved with the chemical evolution stage preceding actual life. He was also hoping desperately, his companions knew, to find a key piece of the biological jigsaw puzzle while he still lived, even if that piece failed to provide a cure for his particular ailment. He was as close to being a pure idealist as anyone in the group—a scientific Nathan Hale, though no one was tactless enough to make the comparison aloud.

	The screen brought Belvew's attention back from this brief wandering. Ginger had started to rise from her squatting position, and was putting on a rather grotesque show.

	She had been slightly off balance as she straightened her knees, and reached vertical with her center of gravity a little outside the support area outlined by her feet. There is a normal human response to this situation, acquired usually during the first year or so after birth: one picks up the foot nearest the direction of tilt and moves it farther in that direction to extend, the support area, though not so far as to make reaction initiate a fall the other way. The woman started to do this, but her right food refused to pick up. The couple resulting from pull on this one and Third Law push on the other tilted her even farther to her right. By the time she reached thirty degrees all eyes were on their screens, and at least three theories were being developed.

	"You've melted yourself in!" cried Martucci. Inger, whose idea involved close contact between soles and surface plus Titan's high air pressure, said nothing but thought furiously. Goodell, already wondering how simple the chemistry for a thermotropic reaction could possibly be, called, "See whether it's pulling in around your boots, or if you're just sinking!"

	Ginger Xalco was moved to answer this. "Just sinking? I'm stuck, you idiot! What do I do?"

	"Find out why," Arthur replied calmly from the safety of a seven hundred kilometer high orbit.

	"Try to tilt and slide one boot at a time," proffered Inger. "Can anyone guess how much jet exhaust a suit will take?" asked Belvew. "I assume no one knows."

	While the woman tried unsuccessfully to implement Barn's suggestion, and then less enthusiastically to follow Goodell's instruction, Gene, already in his waldo suit, silently preflighted Theia. Xalco had filled the tanks conscientiously on the way down, and the landing had depleted them only a little; there was well over enough for a takeoff. Keeping careful watch on the gauges he fired up the plasma arcs and fed liquid to the pipes. Carefully checking the relative whereabouts of woman and factory, but not letting himself worry about a few labs, he raised thrust on the right jet enough to drag Theia in a curving trail—the keels wouldn't let it simply pivot—until it was heading toward Ginger. He then equalized both sides and sent the machine dragging forward until it was only fifty meters from the still anchored suit. Rather than attempt another tight turn he went on past, leaving Ginger on his left and turning only slightly to the right, until the exhaust was streaming past her only three or four meters away.

	"Better let me take it," the woman said at this point. "I can tell if it's too close, and the response will be quicker." Gene made no argument, and relinquished control. Using waldo while standing up was more awkward than Ginger had expected, and for a few seconds she was almost tempted to let Belvew take over again; but she resisted the urge, recognizing the strength of her own arguments and possibly for other reasons.

	The jet blast was now sweeping over part of the patch, behaving just as it had before: the tar, it that's what it was, was sinking or possibly vaporizing into a shallow groove along the track of the warm gas, while a dark cloud of smoke appeared above the affected region and swirled and billowed slowly away from Theia.

	Ginger examined as closely as she could the slow widening of the trench, and very carefully increased thrust on the left pipe to swing the gas stream closer to her position. The higher power widened the stream as well as turning the jet, and she almost overdid it. The unspoken question in all minds was whether the removal of surface could be managed without cooking her suit. She finally stopped the turn by cutting back on the left unit and raising power in the other. Luckily this did not provide enough total thrust to move the aircraft farther away and complicate matters even farther.

	"I still can't tell whether it's vaporizing, melting and sinking, or just crawling out of the way," she reported, her voice once more calm.

	"Is it crawling over your boots?" asked Goodell. Xalco squatted once more.

	"No," she replied after a moment. "It's more like melting in. I'm deeper than before, but the stuff isn't closing in around me. You know, this might work."

	"Damn!" said Arthur with feeling. Not even Ginger criticized. All watched tensely while the trench widened toward her and finally reached the left boot. Here it seemed to stop, and after several impatient minutes she raised the thrust a few percent.

	"Your tanks are getting a bit—" Gene didn't even try to finish the sentence. Ginger answered only by trying, hard, to slide her boot toward the once more widening trench.

	The material which had pressed up and outward like fairly stiff clay around the sole was vanishing; she squatted to watch closely, curiosity once again in the ascendant, as it blew away in a trail of smoke which she could clearly see forming from half a meter. She reported verbally to the others.

	"Can you move your foot?" cried Belvew. "Your tanks!"

	She stood and pushed sidewise again, and her left boot slid out into the exhaust stream, suddenly free.

	She brought it next to the right one and pressed down hard; it had, after all, taken a while for her to 'stick' earlier. She kept trying, shifting the position of the free boot every few seconds just in case, but the right one stayed firmly in place until the warm gas actually reached her armor and began to eddy around it. For several more seconds no one breathed, much less spoke; then the right foot came suddenly free, and Ginger made an unplanned but quite lengthy jump which took her off the smooth patch.

	If the released breaths from the watchers had been free to leave the station, its orbit might have been changed measurably.

	Ginger, safely on ordinary ground, did not make her way at once back to the jet. She picked up, labelled, and pouched several dirt samples from points as close to the edge of the patch as she could move the stuff. She even made a point of working loose a specimen where soil and smoothness seemed to blend. Then, without haste, she returned to the aircraft and vanished from the screens.

	"Don't hit the factory on takeoff!" Arthur cried, then, "Sorry."

	Ginger made no answer. A few seconds later Theia slid into the air, and a minute after that had reached ram speed with something under a hundred kilograms of mass in her tanks.

	"There's a thunderhead at forty kilometers, two hundred degrees," Maria informed her.

	"Right. Thanks. Is there anything I should do while I'm here, after I juice up? Or have I already earned a mission credit? I did pick up a lot of data."

	Belvew wondered whether she would have thought of using the jet to free herself, but was far too polite to suggest this explicitly.

	"How about splitting the credit?" he asked innocently.

The End