“But that doesn’t mean the Builders must be gone completely. Maybe they are still around in other parts of this arm.”
“They might be. I’m quite willing to admit the possibility of two races of super-beings. But you know how Julian Graves reacted. He talked about the ‘undesirability of concatenating implausibilities.’ As if we were not sure of the existence of the Builders themselves, when we have seen evidence of their existence all over our own spiral arm. I’m hoping that what we find on Iceworld will persuade Julian Graves to change his mind.”
“My idea wasn’t new, was it? You had the same thought yourself, long ago.”
“Possibly something very like it. But keep thinking. It could be that the Builders became extinct when they stopped thinking.”
“You don’t really believe that, do you?”
“No, I don’t. On the other hand, I’ve been wrong about the Builders so many times in the past, you shouldn’t accept my views—or anyone else’s—as gospel.” Darya saw that Rebka and Blesh were examining something in the autochef, and Ben Blesh was laughing. She concluded, “If you have more ideas when we reach Iceworld, I’d like to discuss them.”
It was intended to be an easy way to end the talk and hurry over to protect her own stomach, but it produced a surprising response. Lara lowered her voice and said, “There is something else I’d like to talk you about. But not right now. I want to speak privately.”
It didn’t sound as though Lara wanted another conversation about the Builders. That was a pity. Darya herself would be more than ready for that, especially after they’d had a chance to examine Iceworld.
Maybe Hans was right after all. Maybe “obsession” was the best word for it.
They had traveled to an alien arm of the galaxy where humans had never been before. They were within an alien star system, and only a day ago they had left a dead and alien world. But alien was relative. There were degrees of alienation. The planet they had come from, with its air and oceans and mountains and what had once been a thriving civilization of intelligent beings, felt like home compared with Iceworld.
Darya sat by Hans Rebka’s side and alternated her attention between the displays of the ship’s sensors and the planet around which the Savior now orbited. She had to think of it as alternating attention, because they could not see the world in any conventional sense. To human eyes, Iceworld was no more than darkness visible, a black disk revealed by the absence of the stars that it occulted.
Every other imaging sensor, at every frequency from hard X-rays to long-wavelength radio, told the same story. They detected no emitted signal. The planet was simply not there. Only one seldom-used instrument, a low-resolution imaging device normally used to measure cosmic background radiation, admitted a presence. It reported a unique world where the maximum temperature was little more than one kelvin, and that only in isolated places. In many places the temperature was too small to register—which meant that it had to be less than one hundredth of a degree absolute.
Nothing in the universe was so cold, nothing in the universe could be so cold. Radiation falling onto a planet’s surface must warm it, raising it at the very least to the 2.7 kelvins of the cosmic microwave background.
“So it doesn’t exist,” Rebka said. “But there it is.”
“Will we be going down?” Ben Blesh was crowding Darya, pushing her aside in his eagerness to see everything.
“Eventually.” Rebka was in the command pilot’s seat. “Before that happens I’d like to learn as much as we can from orbit. It may take a day or two, but I want to fly over every square kilometer and tickle the ground with something a bit more active.”
The Savior was moving along a spiraling orbit that would in time cover Iceworld’s whole surface like wool being wound evenly onto a great ball. The ship was less than two hundred kilometers above the surface. Such a close orbit would normally decay rapidly because of air drag, but Iceworld lacked the faintest trace of an atmosphere. The planet also seemed perfectly spherical. The gravity field supported the idea of an equally symmetrical interior, and nothing perturbed the Savior’s flight. Only Rebka’s natural caution prevented them from flying lower yet, fifty kilometers or five kilometers up.
“What do you mean, tickle?” Darya asked. “Don’t damage anything down there, Hans. I want to see the place in its unspoiled condition.”
“It’s a big planet, Darya. Twenty times the surface area of Miranda. And we’ll only be using the laser in a pulse mode, one burst every five seconds. Don’t worry. We’ll get enough burn to give us an emission spectrum for the points of impact, but we’ll be touching less than a billionth of the total area.”
“We’ve never experienced anything so cold before. Can you be sure you won’t ruin anything?”
“Not completely sure. But if it’s a choice of risking a little local damage down there, versus risking our skins when we descend, which do you prefer? Hmm.” Rebka was peering at a screen that displayed a graph composed of sharp peaks and valleys. “Darya, this is the return spectrum—it looks the same for every laser pulse. But it seems your name for the planet wasn’t the greatest choice.”
“Iceworld?”
“Right. This is a spectrum of the raw return signal, and over there we have the results after the spectrum analyzer has done its work. It’s reporting not a trace of ice—any kind of ice. No water, no carbon dioxide, no methane, no oxygen, no nitrogen, no chlorine, no fluorine.”
“No condensed gases of any kind?”
“Worse than that. The spectrum doesn’t match any material in our spectral signature library, solid, liquid, or gas. You were right, Darya, this place wasn’t formed naturally. It’s not made of any known material.”
“Are you sure that our laser isn’t disturbing things below the surface?” Lara Quistner was watching another display, this one showing a larger area than the immediate vicinity of the illuminated spot.
“As I said, not so we should notice.” Hans Rebka checked a dial. “We’re at low power and long wavelength. The top tenth of a millimeter of the ground should account for all the return.”
“Maybe it does—or maybe low power means something different down there. Do you want to see what I think I’m seeing? Zoom in on a line that trails behind the laser beam, and wait.”
It took a while, because as long as the moving light of the laser was in the field of view it dominated what the eye could detect. Even when the image moved far enough to put the pulse out of sight, Darya was at first convinced that Lara was imagining things. At last she saw it, so faint that it was at the very limit of visibility. A blue glimmer like a dust devil spurted up at the place where the laser beam had hit. It seemed to boil out of the surface for a moment, then was gone.
Lara whispered, “They come about twenty seconds after the laser has moved on. What are they?”
“No idea.” Rebka was changing control settings. “Let’s try some signal enhancement, see if we can get a spectrum we recognize.”
Before he could finish, a flash of orange startled their eyes. It was bright enough to obliterate all signs of the blue dust devils, then at once it too had vanished. Darya was left with a zigzag afterimage like a bolt of lightning. She blinked, waiting for her retinas to adjust after the overload.