by Hal Clement
Maria looked around thoughtfully. As she had said, the rain seemed to have ceased. So, not too surprisingly, had the rill trickling along the foot of the cliff. She had already dismissed this as just part of the drainage pattern which returned most of the crater’s rainfall to the central lake and made Settlement Crater a nearly closed weather system.
Water ice is too polar to be at all soluble in liquid methane, and Maria had not been surprised that the temporary brook showed no signs of having cut into the foot of the cliff, not even when she was thinking of possible ways to date the latter. Neither had Ginger Xalco, who had been first on the scene and had started the tunnel. Now something she didn’t remember seeing earlier caught Maria’s eye, and she looked at it thoughtfully for a moment.
“Ginger!”
“Yes?”
“When you started to dig, I know there was no stream along the cliff, so there was no reason to make a sill. Did you start the hole right at the bottom of the face, or a little bit up?”
“At the bottom, of course. We agreed on that, remember? We didn’t want anything to interfere with bringing heavy stuff inside. It was just starting to rain when you took over, and you had water—I mean methane—inside in two or three minutes. That’s why you had to make the sill.”
“That’s how I remember it. Now I see about three millimeters of cliff outside and below the sill. Status, how fast could that stream eat its way down—remembering that it doesn’t seem to undermine the cliff or cut the ground at all?”
“It couldn’t.” Two voices besides that of the computer answered simultaneously.
“Then what, besides a three millimeter lift of the cliff itself since I built the sill, could have happened here?”
Neither Status nor anyone else answered that one. Maria thought furiously for some seconds—no more furiously than any of the others, but she spoke first.
“Status, what summary do we have on this crater? And how far back does the information go?”
“I assume you mean in time,” the computer answered. “There is very little, actually. The area had not been covered by the regular mapping program when Commander Goodell first centered his attention on it. His original data came from jet-based pictures taken from altitudes too high for good data, because of poor air transparency and the jet camera resolution. When he became really interested in the site he secured more material from orbit without calling either your attention or mine to it; I now find that I have good pictures over a period of about one Titan orbit, ending about eighty hours before his landing. I cannot show you these where you are; you would have to come up here or at least board a jet. I can, of course, give verbal and numerical descriptions. If someone will make appropriate requests I can present current data quite soon.”
“What I want to find out is how high this cliff was when Arthur did the area, and most important, whether that height has changed enough to measure since then.”
“I can answer that immediately, since I have your description of the cliff. It was not there at all when Commander Goodell made his investigation.”
“And you never noticed the difference when we started to dig?” asked Yakama.
“The matter was not specifically brought to my attention. Commander Goodell had not filed his information with the regular survey records, so I did not include it in my ongoing comparisons. When the scarp was first noticed and selected for the tunnel site there was therefore nothing to compare it with.”
Maria cut in. “We understand that. Now, Status, do everything you can to make sense out of the fact that the cliff is here now. Especially, tie it in as closely as you can with all the seismic data we have; it looks as though Titan may be alive in a very different sense from what the Project had in mind. And check over all the surface data we have, from the very beginning, to see whether anything of this sort has been happening anywhere we do have records for. Have quake waves from this area reached any of the cans yet?”
“Nothing identifiable as such. As I said, there is frequent seismic activity. What you ask will take some time—not much for record search, but possibly a great deal for comparison and analysis.”
“Just a moment. Another question. There’s some more vibration—Status, I’m at the foot of the cliff, on the side of the fault which should be staying put or going down. It’s the cliff which should be rising. Why was I just tossed into the air?”
The living listeners, the ones with imaginations, said nothing; each was furiously seeking a reasonable, or at least possible, answer to this question. Status alone replied, posing another question which could not have been more annoying to Maria if it had actually been guided by malice.
“How high were you thrown?”
She yielded for a moment to the irritation and answered sarcastically, “Seventy two point three one four millimeters.”
“Center of gravity or boot soles? and how was that measured?”
“Disregard that datum.” She had command of herself again. She was also back on the surface, still standing, and for a moment thought of using her time off the ground to calculate the height she had reached. Then she realized she had no accurate estimate of that, either. But even a guess would mean something, she reflected. “I was off the ground about three seconds. That’s only an estimate.”
“Were your legs straight, or equally bent before and after the event?”
“Straight. I was simply standing when it happened.”
“Then you were lifted approximately one hundred fifty-one centimeters, with an uncertainly depending on the square root of your time estimate error. With your suited mass of two hundred ten kilograms, the force against your feet must have been—”
“Dammit, I don’t care about that. I’m on the down side of the cliff. Why was I thrown up?”
Belvew beat the computer to a response. “Has the three millimeters of cliff under the sill changed?” Maria had to pause to check before answering; being hurled into the air, even when one comes straight down again in practically the same place, is disconcerting.
“It’s about the same. I only estimated it before.”
Status cut in. “I advise setting up two more lines of seismometers each one hundred kilometers long, at right angles to each other, and intersecting as close to the center of Settlement Crater as may be practical. There are enough cans already manufactured to do this.”
“Where?” asked Belvew.
“Aboard Crius,”
“Which is headed up to you. Are there any on Theia?”
“Enough for about half of one of the lines I suggested.”
Maria made an instant decision, and used her authority. Like the others, she needed no explanation why Status wanted the on-the-spot deep scan. “Get Theia here as fast as possible, and have it make the two lines with four times normal can spacing. You can get lots of information, even if resolution won’t be as high—blast! I just got tossed again. We are really having quakes. And this time the three millimeters went up to about five. The cliff went up; I should have had the ground drop from under me, if anything. What’s happening?”
“How high were you thrown this time?”
“Is there another cliff somewhere behind you?” came the questions of Status and Belvew simultaneously.
“I didn’t notice this time, either.” Collos took the machine’s question first. “I wasn’t expecting it. Get that jet over here! Who’s driving it now?”
“I have it. On the way,” responded Ginger Xalco’s voice. Belvew repeated his question.
“I haven’t seen one, but if I’m on the high side and it’s any distance away I wouldn’t expect to. Which is more important, Status? Going west to find another fault, which is probably there but probably not important, or getting back to work on the tunnel?”
“Stay out of there!” Ginger and Belvew’s cries were almost together.
“Check the tunnel as far as you can see without actually entering it, for evidence of new faults,” was the computer’s contribution.
&nb
sp; Maria glanced toward the top of the scarp, and then to each side along its foot. Neither ice nor sediment seemed to have been shaken down by the recent shocks; and if anything were, she reflected, it wouldn’t be falling far or fast. She could dodge, and if she didn’t dodge fast enough the stuff wasn’t likely to be dangerous. They did need to know as soon as possible whether the whole idea of an underground station would have to be abandoned. Could they build any sort of surface structure? How? From what materials?
The choices were ice and smog sediment—tar dust. She was distracted from the problem for a moment as the ground trembled again, not hard enough this time to throw her clear of it. Aftershock? Was the show nearly over? Would Status be able to decide about that even with the new lines in place?
The computer was not, of course, infallible; should she follow its rulings—no, suggestions—uncritically?
Of course not; but she couldn’t act without them, either. She resisted the urge to call Ginger to hurry; Theia was, she was sure, at full thrust already.
“Any faults in the tunnel?” Belvew’s voice recalled her to the present.
She approached the opening, and, after a moment’s hesitation, took a single step inside. At least the sediment at the cliff top, which seemed more likely than the ice to be knocked free by any more temblors—it was a dirt-compared-to-rock situation, really—wouldn’t hit her here. She examined the tunnel walls carefully with the aid of a hand light. Even Titanian outdoor light below the smog was seven or eight stops darker than a sunlit Earth landscape.
“I can’t see anything,” she said at list. “The walls aren’t perfectly smooth, but the only grooves I can see are along them. I must have made them myself with the digger.”
“You should resume digging,” said Status calmly.
“No you don’t!” Belvew almost screamed. Maria frowned silently for a moment.
“Sorry, Gene,” she said. “We need the new station.”
“Not the way we need live brains!”
“I think it’s safe enough.”
“How safe is safe enough—oh.” The man fell silent. The commander gave no answer, but started back down the tunnel.
“You wouldn’t have let me do it.” Gene’s voice was much quieter.
“You don’t know that.” Maria resumed work with the chipper.
“Nehemiah Scudder didn’t know the earth was made in six days.” Belvew omitted the “he just believed it” part of the remark; there was no point either in being grossly insulting or leaving himself open to a devastating retort. Maria probably wouldn’t have made one, but still . . .
The rest of the group were all listening, after all.
“I’ll be there in about ten minutes,” Ginger interjected tactfully. “I’m letting down now. Status, does the absolute direction of the can lines matter? You said to make them at right angles to each other, but nothing more.”
“Even the right angle needn’t be exact,” was the answer. “In any case, the absolute orientation will be known when we calibrate them. You can drop the first one on your initial pass over the crater.”
“Only if you tell me when I’m at the right distance. I know I’m heading right, but I can’t see far enough ahead to spot the crater from fifty k’s out.”
“I can take care of that,” came Manucci’s voice. “I have your position and vector through one of the relays—the Station is below your horizon. Tell me when you’re down to drop height.”
“Five more seconds,” the pilot answered promptly.
“Then cut to sowing speed right now, or you’ll overshoot.”
“Right.” Both speakers were physically in the Station, of course; it would have been easier to let Pete take over the jet directly had he been competent to fly it. No one mentioned this.
“You start to drop in six minutes from—NOW. Remember the wide gap on these lines; is your intervalometer reset?”
“It is now. Thanks. Maria, any more jolts?”
“Yes, but nothing to send me off the floor.”
“And nothing to shear the tunnel?” asked Belvew.
There was a brief pause while the digger looked back along the bore. “Nothing I can see inside. Ginger, is anything funny ahead? The sky looks paler than usual, at least the little bit I can see through the entrance.”
“Nothing shows from here. Not even the crater, yet. The sky from here is the usual orange-tan, or whatever you like to call it, with a few cumulus. Maybe you’re seeing one of those.”
“Maybe. I can check that out later. I’ll dig until I have to rest again, or until there’s some other reason to go outside, everything here seems solid enough, now that the mud I plastered on the ceiling has all fallen back down. The real shocks seem to have stopped, but there’s a fairly steady continuing vibration.”
“Keep an eye on the tunnel mouth,” Gene suggested. “If the motion along that fault reverses, you could be in a fairly tight spot.”
“Why should it do that? Do they ever?”
“Ask me again when I know why it’s there at all—I mean in detail; we already know Titan builds mountains.”
“And why should I worry? I have the digger with me, and here’s only a few meters of ice overhead.”
“You can’t go straight up. I doubt if you can slant up at twenty degrees. That reads quite a few meters of tunnel. Think time, not distance—Commander.”
“True. I have about twenty-eight hours to go in this suit before tapping emergency storage, and two after that.”
“And that includes two or three to get up here, depending on when you start. At least, take your breaks outside.”
“We should have built recharging equipment into the jets,” remarked Martucci.
“There are a lot of things we’d have done if we’d known enough.” Anyone, including Peter himself, could have made that remark, and most of them did; Seichi beat the rest by a split second. There was silence for a few minutes while Maria continued to chip ice and Ginger’s aircraft approached Settlement Crater.
“Twenty seconds to first drop. You’re on heading, assuming no wind,” Peter announced at last.
“A Titan hurricane wouldn’t make that much difference, I ‘ve set start and interval—there goes the first!”
“Can you see the crater yet?”
“Not at fifty kilometers. I’d guess visibility about twenty, ordinary for this height. I’d rather not play with wave lengths while I fly a line; you’re all getting the same picture, though, some of you can try for more penetration.”
Again Seichi was first; he had probably been scanning the spectrum before Ginger had made her suggestion.
“I have the crater. You’re headed all right, Ginger. There’s something funny there, though.”
“What?” again several voices overlapped.
“A very low cloud, I’d say, nearly white in this wave band. It has a very sharp, straight edge on the west side, running almost north and south. It starts about a kilometer south and three west of the lake, less than a k from the near rim, and runs nearly straight north into the northwest wall. It’s interrupted there, but resumes and continues for at least one crater diameter—seven kilos or so—outside. The cloud itself is about two or three kilos wide, though the east side is a lot less sharp. It fades out pretty well by the time it reaches the north-south diameter of the ring, so I can see the lake all right. That may be what’s lightening your sky, Maria.”
“Should I investigate, or lay out the cans first?”
“The cans.” Status’ voice of course showed no emotion, but the answer came quickly enough to sound emphatic.
“That’s three quarters of an hour at standard, Maria—Commander—maybe you should go outside and at least take a look,” suggested Belvew. “The only clouds I’ve ever seen here are cumulus, formed over lakes and raining back into them or near them. This isn’t connected with the lake.”
“Status?” Maria uttered the one word.
“Sergeant Belvew is probably right. There is a good ch
ance you can obtain useful data.”
“And a better chance of your living though the next big shock.” Gene made no effort to keep the words to himself, but no one else commented on them. Not even Maria.
She kept the chipper with her as she leaned forward twenty degrees or so to Titan walking attitude and started back up the tunnel. The visible area of sky increased as she approached the entrance, but to her surprise she could distinguish no ground even when she was within a few meters of the opening and her line of sight over the sill was very clearly downward. Surely the cliff hadn’t . . .
There was nothing but the vaguely orange-tinted grey, much lighter than the familiar color produced by the suspended smog—tar—particles constantly forming high above.
Only when she was outside and several meters from the scarp did the regular orange-tan become visible to the east, beyond the cliff. Overhead and to the west the color paled steadily until, looking toward where the horizon should be, there was only a featureless and impenetrable near-white.
“I can see it now. It’s moving. It’s blowing from west to east,” came Ginger’s voice. “There must be some wind. Can you tell, Maria?”
The commander took a glovefull of the ice dust which had been blown from the tunnel, raised it to helmet level, faced south, and let it spill from her palm.
“Yes. Not much, even for Titan, but the air’s moving east. More to the point, the surface west of me has been covered with something; it’s almost white, too. That’s why I thought I couldn’t see the ground from inside the tunnel. It’s as near as no matter the same color and brightness as the sky in that direction.”
“Are you still sensing vibrations?” asked Status.
Maria paused before answering. “Yes. I’m getting used to it, I’m afraid. I may not be able to give an objective report about it before long.”
“I suggest you walk slowly westward, looking for changes in visibility and thickness of the white ground covering as you go, Commander.”
