Titan

by John Varley

  Cirocco waited patiently. When no one said anything, she snorted.

  "in the middle of Saturn's satellite system? For about five minutes, maybe. The other moons would perturb them."

  "There's that," Gaby agreed.

  "And how would it happen in the first place? The chances against it are tremendous."

  "There's that, too."

  April and Calvin had entered the room. Now Calvin looked up.

  "Isn't anyone going to say it? This isn't a natural arrangement.

  Somebody made this."

  Gaby rubbed her forehead.

  "You haven't heard it all. 1 bounced radar signals off it. They came back telling me Themis was over 1300 kilometers in diameter. Density figures all cockeyed, too, making it less dense than water by quite a bit. 1 thought 1 was getting screwed-up readings because 1 was working at the limits of my equipment. Then 1 got the picture."

  "Six bodies or one?" Cirocco asked.

  "I can't tell for sure. But everything points to one." "Describe it. What you think you know."

  Gaby consulted her printout sheets, but obviously did not need them. The figures were clear in her mind.

  "Themis is 1300 klicks across. That makes it Saturn's third

  largest moon, about the size of Rhea. It must be flat black all over, except those six points. This is by far the lowest albedo of any body in the solar system, if that interests you. It's also the least dense. There's a strong possibility it's hollow, and a good chance it's not spherical. Possibly disc-shaped, or toroidal, like a donut. Either way, it seems to turn like a plate rolling along its edge, once every hour. That's enough spin so nothing could stay on its surface; the centripetal force would overpower the force of gravity."

  "But if it's hollow, and you were on the inside .

  Cirocco kept her eyes on Gaby.

  "Inside, if it's hollow, it would be equivalent to a force of one- quarter gee. "

  Cirocco looked her next question, and Gaby couldn't meet her eyes.

  "We're getting closer every day. The seeing can only get better. But I can't promise you when I could he sure about any of this."

  Cirocco headed for the door. "I'll have to send what you have."

  "But no theories, okay?" Gaby shouted after her. It was the first time Cirocco had seen her less than happy with what she'd seen through a telescope. "At least don't attribute them to me."

  "No theories," Cirocco acknowledged. "The facts ought to be plenty."

  CHAPTER TWO

  INFORMATIONAL DISPATCH #0931

  (REPLY TO HOUSTON TRANSMISSION #5455,5-20-25) 5-21-25

  DSV RINGMASTER (NASA 447D, L5/1, HOUSTON-COPER- NICUS GCR BASELINE)

  JONFS, CIROCCO, MISCOM

  SECURITY INTERLOCK *ON* CODE PREFIX DELTADELTA BEGINS.

  1. Concur your analysis of Themis as interstellar space vehicle of the generation type. Don't forget we suggested it first.

  2. Latest photo follows. Note increased resolution of bright areas. Still no luck finding docking facilities at hub; will keep looking.

  3. Concur your mid-course scheduled 5122.

  4. Request updated tracking as new orbital insertion is approached, beginning 5125 and continuing until insertion commences, then upgraded. I don't care if this means shifting in another computer 1 don't think our on-board will handle this volume.

  5. Turnaround 5122,0400 UT, after the mid-course bum. 22

  WORMA'EONALENDS PERSONAL (CIRCULATION LIMITED TO RINGMASTER MISSION CONTROL COMMN-TEE) BEGINS:

  Re the Contact Committee which has been bending my car: 'buzz off!' I don't care WHO'S on the damn thing. I've been get- ting contradictory instructions that sound like they have the

  force of direct orders. Maybe you don't like my ideas of how to handle this, maybe you do. The fact is it's going to have to be my show. Time-lag alone is enough to make that necessary. You gave me the ship and the responsibility, so 'GET OFF MY BACK!'*

  ENDS

  Cirocco hit the ENCODE button, then TRANSMIT, and leaned back in her chair. She rubbed her eyes. A few days ago there had been too little to do. Now she was snowed under with the status cheek to ready Ringmaster for orbital insertion.

  Everything was changed, and all by those six tiny points of light in Gaby's telescope. There seemed little sense in exploring the other Saturnian moons now. They were committed to an early rendezvous with Themis.

  She called up the schedule of things still to be done, then the duty roster, saw it had been rearranged again. She was to join April and Calvin outside. She hurried to the lock.

  Her suit was bulky and tight. it murmured at her while the radio hissed quietly. it smelled comfortably like herself, and like hospital plastic and fresh oxygen.

  Ringmaster was an elongated structure consisting of two main sections joined by a hollow tube three meters in diameter and a hundred meters long. Structural strength for the tube was provided by three composite girders on the outside, each of which transmitted the thrust of one engine to the life system balanced on top of the tube.

  At the far end were the engines and a cluster of detachable fuel tanks, hidden from sight by the broad plate of the radiation shield which ringed the central tube like the rat guard on the mooring line of an ocean-going freighter. The other side of that shield was an unhealthy place to be.

  On the other end of the tube was the life system, consisting of the science module, the control module, and the carousel.

  Control was at the extreme front end, a cone-shaped protuberance rising from the big coffee can that was SCIMOD. It had the only windows on the ship, more for tradition than practicality.

  The Science Module was almost hidden behind a thicket of instrumentation. The high-gain antenna rose above it all, perched on the end of a long stalk and trained on Earth. There were two radar dishes and five telescopes, including Gaby's 120-centimeter Newtonian.

  Just behind it was the carousel: a fat, white flywheel. It rotated slowly around the rest of the ship, with four spokes leading up from the rim.

  Strapped to the central stem were other items, including the hydroponics cylinders and the several components of the lander: life system, tug engine, two descent stages and the ascent engine.

  The lander had been intended for exploring the Saturn moons, in particular Iapetus and Rhea. After Titan-which had an atmosphere and was therefore unsuited for exploration this trip-Iapetus was the most interesting body in the neighborhood. Until the 1980's, it had been significantly brighter in one hemisphere, but it had changed over a twenty-year period until its albedo was nearly uniform. Two troughs in the graph of luminosity now occurred at opposite points on its orbit. The lander had been designed to discover what caused it.

  Now that trip had been scrapped in the face of the much more compelling object called Themis.

  Ringmaster resembled another spaceship: the fictional Discovery, the Jupiter probe from the classic movie 2001.. A Space Odyssey. It was not surprising that it should. Both ships had been designed from similar parameters, though one sailed only on celluloid. Cirocco was EVA to remove the last of the solar reflection panels which wrapped the life system of Ringmaster. The problem in a space vehicle is usually one of disposing of excess heat, but they were now far enough from the sun that it paid to soak up what they could get.

  She hooked a safety line around a pipe that went from the carousel hub to the airlock, and faced one of the last panels. It was

  silver, a meter square, made of two sheets of thin foil sandwiched together. She touched the screwdriver to one corner and the device clucked as it found the slot. The counterweight rotated. It gulped the loose screw before it could drift away.

  Three more times and the panel floated away from the layer of anti-meteorite foam beneath. Cirocco held it and turned to face the sun, conducting her own informal puncture survey. Three tiny, bright lights marked where the sheet had been hit by grains of meteoritic dust.

  The panel was held rigid by wires along the edges. She bent two of these in t
he middle. After the fifth fold it was small enough to fit in the thigh pocket of her suit. She fastened the flap, then moved to the next panel.

  Time was at a premium. Whenever possible they combined two chores, so the end of the ship's day found Cirocco reclining on her bunk while Calvin gave her a weekly physical and Gaby showed her the latest picture of Themis. The room was crowded.

  "It's not a photo.," Gaby was saying. "It's, a computer- enhanced theoretical image. And it's in infra-red, which seems to be the best spectrum."

  Cirocco raised herself on one elbow, careful not to dislodge any of Calvin's electrodes. She chewed on the end of the thermometer until he frowned at her.

  The print showed a fat wagon wheel surrounded by broad- based, bright red triangular areas. There were six red areas on the inside of the wheel, but they were smaller, and square.

  "The big triangles on the outside are the hottest parts," Gaby said. "I figure they're part of the temperature control system. They soak up heat from the sun or bleed off the excess."

  "Houston already decided that," Cirocco pointed out. She glanced at the television camera near the ceiling. Ground control was monitoring them. If they thought of something Cirocco would hear of it in a few hours, asleep or not.

  The wheel analogy was almost literally true, except for the heating or cooling fins Gaby had indicated. There was a hub in the center, and it had a hole which could have taken an axle if

  Themis had actually been a wagon wheel. Radiating from the hub were six thick spokes which flared gradually just before joining the outer portion of the wheel. Between each pair of spokes was one of the bright, square areas.

  "This is what's new," Gaby said. "Those squares are angled. They're what 1 originally saw; the six points of light. They're flat, or they'd scatter a lot more light. As it is they only reflect light to Earth if they're at just the right angle, and that's rare."

  'What kind of angle?" Cirocco - lisped. Calvin took the thermometer out of her mouth.

  "Okay. Light comes in parallel to the axis, from this angle." She moved an extended finger toward the print. "The mirrors are set to deflect the light ninety degrees, into the wheel roof." She touched the paper with her finger, turned the finger, and indicated an area between two spokes.

  "This part of the wheel is hotter than the rest, but not so hot that it could be soaking up all the heat it gets. It's not reflecting it or absorbing it, so it's transmitting it. It's transparent or trans- lucent. it lets most of the light go through to whatever's underneath. Does that suggest anything to you?"

  Cirocco looked up from her careful examination. "What do you mean?"

  "Okay. We know the wheel is hollow. Maybe the spokes are, too. Anyway, picture the wheel. It's like a car tire, big and fat and flat on the bottom to give more living space. Centrifugal force pushes you away from the hub."

  "I've got all that," Cirocco said, slightly amused. Gaby could he so intense when explaining something.

  "Right. So when you're standing on the inside of the wheel, you're either under a spoke, or under a reflector, right?"

  "Yeah? Oh, yeah. So-" "So it's always either daytime or nighttime at any particular spot. The spokes are rigidly attached, the reflectors don't move, and neither can the skylights. So it has to be that way. Permanent day or permanent night. Why do you think they'd build it that way?"

  "To answer that, we'd need to meet them. Their needs must he different from ours." She looked back at the picture. She had to keep reminding herself of the size of the thing. Thirteen hundred meters in diameter, 4000 around the outer rim. The prospect of meeting the beings who built such a thing was worrying her more each day.

  "All right. 1 can wait." Gaby was not that interested in Them- is as a spacecraft. To her it was a fascinating problem in observation.

  Cirocco again looked at the picture.

  "The hub," she began, then bit her lip. That camera was still running, and she didn't want to say anything too hastily.

  "What about it?"

  "Well, it's the only place you could dock with the thing. The only part that's motionless."

  "Not the way it is now. That hole in the middle is pretty big. The first time you reach anything solid, it's moving at a pretty good clip. 1 can calculate-"

  "Never mind. It's not important right now. The point is, only at the very dead center of rotation could you dock with Themis without a great deal of trouble. 1 sure wouldn't want to try it."

  "So? "

  "So there must be a compelling reason why there's no docking facilities visible there. Something important enough to sacrifice that location, some reason for leaving a big hole in the center."

  "Engine," Calvin said. Cirocco glanced at him, got a glimpse of his brown eyes before he turned back to his work.

  "That was my thought. A real big fusion ramscoop. The machinery is in the hub, electromagnetic field generators to funnel the interstellar hydrogen into the center, where it gets burned."

  Gaby shrugged. "Makes sense. But what about docking?" "Well, leaving the thing would be easy enough. just drop out a hole in the bottom and get escape velocity for free, plus some to fool around with. But there ought to he some sort of dingus that would telescope out to the center of rotation when the engine isn't running, to pick up scout ships. The main engine has to he there. The only other way would be to space engines around the rim. I'd want three, at least. More would be better."

  She turned to face the camera. "Send me what you can about hydrogen ramscoop engines," she said. "See if you can give me some idea of what to look for if Themis has one".

  "You'll have to take your shirt off," Calvin said.

  Cirocco reached up and switched off the camera, leaving the sound on. Calvin thumped her back and listened to the results while Cirocco and Gaby continued to study the picture of Themis. They came up with no new insights until Gaby brought UP the matter of the cables.

  "As far as 1 can tell, they form a circle about midway between the hub and the rim. They support the top edges of the reflecting panels, sort of like the rigging on a sailing ship."

  "What about these?" Cirocco asked, indicating the area between two of the spokes. "Any idea what they're for?"

  "Nope. There's six of them, and they run midway between the spokes from the hub to the rim, radially. They pass through the reflects panels, if that tells you anything."

  "Not exactly. But if there's any more of these things, maybe smaller ones, we should look for them. These cables are about- what did you say? Three kilometers around?"

  "More like five."

  "Okay. So one that's just a tiny thing-say about as big around as ringmaster-might be invisible to us for a long time, especially if it's as black as the rest of Themis. Gene's going to be nosing around there in the SEM. I'd hate for him to hit one."

  "I'll get the computer on it," Gaby said. Calvin began packing his equipment.

  "As disgustingly healthy as usual," he said. "You people never give me a break. If 1 don't try out that five-million-dollar hospital how am 1 going to make them believe they got their money's worth?"

  "You want me to break somebody's arm?" Cirocco suggested.

  "Nah. I already did that, back in medical school."

  "Broke one, or fixed it?"

  Calvin laughed. "Appendix. Now there's something I'd like to try. You don't hardly get busted appendixes anymore."

  "You mean you've never taken out an appendix? What do they teach you in medical school these days?"

  "That if you get the theory right, the fingers will follow. We're too intellectual to get our hands dirty." He laughed again, and Cirocco could feel the thin walls of her room shaking.

  "I wish 1 knew when he was serious, " Gaby said.

  "You want serious?" Calvin asked. "Here's something you might never have thought of. Elective surgery. You folks have one of the best surgeons around-" He paused to allow the rude noises to die away. "One of the best surgeons there is. Does any- one take advantage of it? Not hardly. A nose job, now
that's going to cost you seven, eight thousand back home. Here you got it on the Blue Cross."

  Cirocco drew herself up and gave him an icy glare. "You couldn't he talking about me, could you?"

  Calvin held out a thumb and sighted along it to Cirocco's face, squinting. "Of course, there's other types of elective surgery. I'm pretty good at all of them. It was my hobby." He moved his thumb lower. Cirocco aimed a kick at him and he ducked out the door.

  She was smiling when she sat down. Gaby was still there, the picture tucked under her arm. She perched on the tiny folding stool beside the cot.

  Cirocco raised one eyebrow.

  "Was there something else?"

  Gaby looked away. She opened her mouth to say something, didn't manage to make a sound, then slapped her bare thigh with her palm.

  "No, I guess there wasn't." She started to get up, but didn't. Cirocco looked at her thoughtfully, then reached up and

  turned the television sound off. "Does that help any?"

  Gaby shrugged. "Maybe. I would have asked you to turn it off anyway, if I could ever have started talking. I guess I figure it's none of my business."

  "But you felt you ought to say something." Cirocco waited. "Yeah, okay. It's your business how you run this ship. I want you to know I realize that."

  "Go on. I can take criticism."

  "You've been sleeping with Bill."

  Cirocco laughed quietly. " I don't ever sleep with him. The bed's too small. But I get the idea."

  Cirocco had hoped to put Gaby, at case, but apparently it hadn't worked. Gaby stood and paced slowly, even though she could only go four steps before she reached the wall.

  "Captain, sex is no big thing to me." She shrugged. "I don't hate sex, but I'm not all that crazy about it, either. If I don't have sex for a day or a year, I don't even notice it. But most people aren't like that. Especially men."

  "I'm not like that, either."

  "I know. That's why I wondered how you.... just what your feelings are toward Bill."