“In the other twist, there was no argument that a shaft in the ice of the dark hemisphere, eventually reaching rock some five hundred kilometers down, might well secure reasonably complete information. The dispute, as you know, was over its location. Most useful fossils were expected to be microscopic, things like spores blown to the dark side as dust. We did not know during the planning stage that many more large plants grew in this hemisphere than anyone expected. We still don’t know about animal or equivalent life here. These may leave informative remains, and the wing found a few days ago offers real hope that we may some time find a more complete flier, even one of the present Habras’ remote ancestors.
“However, many felt that more should have been learned about glacial movements before starting the Pits anywhere. Others insisted that such research, while useful and interesting, would take too much time and delay the actual search for meaningful remains. Attractively intense feelings were generated on both sides of the discussion, even among such placid beings as the Samians. Even more remarkably, these feelings did not smooth out after debate ended and it was decided to start digging without complete ice flow data.
“Once we had begun, of course, talk about the alternative line of action became unpopular; administrators dislike even to consider, much less to admit, that their projects may not have had optimum planning. This seems true of all the Six Races, as well as many which are not star travelers, not just my own.”
Hugh rather sympathized with administrative altitudes on this point, and began to wonder whether S’Nash were simply leading up to suggesting a new site for the Pits. He himself saw no reason to keep argument alive on the matter; spending potentially useful time in the “if only we had…” mode irritated him.
“I would certainly not want to waste already expended effort, and I do expect useful and interesting results from the present dig,” S’Nash went on. “I want, however, to keep track of any other work in the dark hemisphere. I want to see studies of the subsurface flow of the ice encouraged. If it does turn out that the Pits are not at the best possible place, I can stand it, of course; they’ll still be useful while they last. A lot of native Habras agree with me about all this; I am not — Rek and I are not — a couple of lone malcontents. We don’t want to hamper this project or lose touch it with, but we want to keep contact with any others going on.”
“And this led to your test of the robot?” keyed Hugh.
“Yes.”
“How?”
“Rekchellet, shall I explain, or would you rather take over?”
“You talk. I’ll draw.”
“Good. You both know Rek’s skills.” It was a statement; the Naxian knew that the flier and the Cedars had worked together before. Neither bothered to answer.
The Crotonite pulled from his harness the drawing pad and stylus he always carried. S’Nash waited silently while its/his partner made a few test marks and cleared the table again in readiness for use. Then it/he resumed talking.
“The upper winds carry water and other volatiles— ammonia, hydrogen cyanide, carbon dioxide — from the sunward side. These eventually fall as snow. In the amplest picture, this snow becomes ever deeper, compressing its lower layers and forcing them to flow back as glaciers toward the warmer hemisphere. In fact, all this motion is heavily complicated by the continuous impacting of the snow into ice, and the ice itself into various phases of differing densities, viscosities, melting points, and mechanical strengths at increasing depths.” So far Rekchellet was making no diagrams; S’Nash was summarizing common knowledge.
“Most snow falls relatively near the warm edge of the dark hemisphere, the terminator, but traces of water and even more ammonia remain in the upper winds even near the dark pole and precipitate there, though much more slowly. Most of the carbon dioxide gets that far. Even if the material did not arrive as gas, gravity would make ice formed nearer the terminator flow downhill, so glaciers exist even at the cold pole, and have thickness comparable to the five hundred kilometers near the boundary — the same as the depth of liquid ocean on the sunward side. The lithosphere of Habranha has to be pretty well centered in the hydrosphere, whether the latter is solid or liquid.
“How much of that thickness stems from ice deposited near the terminator and flowing away from the warm side and how much got there as local precipitation, we simply don’t, know.”
This was still obvious, but the Crotonite did a quick sketch to illustrate the situation. His reason soon became clear.
“Material from these remote glaciers also circulates, though far more slowly. The generally chaotic-situation induced by phase change on Habranha seems to apply in solid as well as in liquid and gas; calculations — mathematical models — fail to agree on the speed and often even the direction of such circulation. No one has been able to decide whether fossil-bearing dust deposited far away from the terminator will or will not make up in age for what it will presumably lack in quantity. You have already found, Janice, that ordinary stratigraphy is as complex in the ice here as in the silicate crusts of more everyday planets. Many of us, as I said, felt that we should not have started to dig until this point had been clarified.”
Neither Hugh nor his wife was surprised at S’Nash’s increasing self-identification with the disapproving party. Rekchellet had started indicating with his usual near-magical clarity currents traveling in various directions in the deep ice of the dark hemisphere. The Erthumoi moved closer to see more clearly; the drawing surface was small.
The diagram included suggestions of flow up toward the surface in places. Neither Erthuma had ever heard such a possibility suggested. It was reasonable enough, though, Hugh reflected; even pure water-ice had phases of differing densities, and on Habranha it would never be pure. There’d be a fair amount of ammonia toward the center of Darkside— more than around here, certainly— and maybe — no, the hydrogen cyanide would be cleared out pretty completely long before that point by the ammonia itself.
“We could check surface ice for N-H-4-C-N,” he keyed. “That would tell us lots even without boring. But how would you get detailed information of ice motion at depth?”
The Naxian’s long form tightened from its heretofore relaxed spiral, and the brilliant gold-brown eyes looked out of their helmet straight into Hugh’s face guard. It took no Naxian sense to tell that a point of intense interest and major enthusiasm to the speaker was coming up. There was a brief pause while only howling wind and hissing snow could be heard.
“Do you know anything about seismology?” it/he asked.
“I know what it is. A sort of quick-and-dirty method of judging the nature of subsurface strata from the way they transmit, reflect, and refract sound waves.”
“Nearly correct, granting a rather broad use of the word ‘sound.’ Your term ‘quick-and-dirty’ is wrong unless my translator badly misjudged its implications. With enough measurements, vast details about the shapes, sizes, depths, compositions, and even motions of the wave-carrying strata may be secured. It’s a common technique. It could be done here. Can you imagine the usefulness of a complete chart of the ice currents of half a world? How it could be applied to quicker, more random liquid and gaseous circulations? What it would mean to the Habras, who have known for ages that their population saturates their world, in their endless problems with their own environment? How it would help the project we are doing right now? Janice, we could even predict where fossils of a given age might be found, and recover them with minimal effort and expense, instead of digging these huge Pits and going through all the complexities of taking laser readings from one to the other to study the dust motes between. We could…”