Titan (GAIA) (3 page)

Cirocco looked at it for a long time.

“It’s the damdest thing I ever saw on a starplate,” she conceded. “What is it?”

Gaby was strapped to a chair on the other side of the compartment, sucking coffee from a plastic bulb.

“It’s the latest exposure of Themis,” she said. “I took it over the last hour with my most sensitive equipment and a computer program to justify the rotation.”

“I guess that answers my question,” Cirocco said. “But what
is
it?”

Gaby waited a long time before replying, taking another sip.

“It is possible,” she said, sounding detached and dreamy, “for several bodies to orbit around a common center of gravity. Theoretically. No one’s ever seen it. The configuration is called a rosette.”

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. I 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. I thought I was getting screwed-up readings because I was working at the limits of my equipment. Then I 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 roiling 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 be 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 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.”

INFORMATIONAL DISPATCH
#0931

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

5-21-25

DSV RINGMASTER (NASA
447
D, L
5/1,
HOUSTON-COPERNICUS GCR BASELINE)

JONES, 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 5/22.

4. Request updated tracking as new orbital insertion is approached, beginning 5/25 and continuing until insertion commences, then upgraded. I don’t care if this means shifting in another computer; I don’t think our on-board will handle this volume.

5. Turnaround 5/22, 0400 UT, after the mid-course burn.

INFORMATIONAL ENDS

PERSONAL (CIRCULATION LIMITED TO RINGMASTER MISSION CONTROL COMMITTEE) BEGINS:

Re the Contact Committee which has been bending my ear: *buzz off!* I don’t care WHO’S on the damn thing. I’ve been getting 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 check 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 re-arranged 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 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 Saturnian 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 occured at opposite points on its orbit. The lander had been designed to discover what had 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 the 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 I 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 translucent. 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 be 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?”