“How far down did all this happen?” asked Molly.
“Three hundred five kilometers below the cave at which I entered. That’s radial component, not along the travel line.”
“And what’s the temperature there? I know your little robots can’t read it, but surely you have a thermometer in the one you’re riding.” For just a moment, Molly’s breath stopped; if Joe had forgotten that item, she had phrased the remark very tactlessly. Fortunately he had not.
“I read two hundred eight-three.”
“That’s only a little higher than we have. I wouldn’t have thought we could possibly be anywhere near your depth.”
“You may not be. I have a cold wind following me from the surface, and silicate is a poor conductor with a fairly low heat capacity. The temperature deep in the rock around me may be a great deal higher. You are getting air from inside…”
“But a river from outside.”
“True.” Except for the one-word response, Joe ignored the interruption; Molly blushed unseen even by Carol. “Nevertheless, I could be deeper. We will know in due time. I have all my mappers back in service now and am heading deeper myself. It will be interesting to learn whether this porosity extends all the way to Enigma’s center.”
“And what the temperature is there,” added Carol. “I wonder how far down this river will last and how far down the life will go, even if they both turn to water. Onward and downward, comrade.”
“And how stable the caverns at the center are, if they do exist,” added Charley.
“I told people to accompany that thought with the word creep,” Molly said firmly.
“Sorry. I’ll be with you, if these rivers do join up. If we do get flattened, it will creep down on us together.”
“Good try” was Molly’s dry retort.
Joe, traveling by far the fastest, made the next report of real interest, but this was not for several more hours. In the meantime the other three explorers had all gone deeper, presumably by several kilometers, and the river followed by the women was now well above the melting temperature of ice. Molly was following this phenomenon with interest that surprised even Carol, stopping for analysis and thermometer check far more frequently than the Shervah wanted. The Human was following another idea of her own, though she had kept it to herself so far. Ammonia was now below the detection limit of the simple instrument in Carol’s armor. Ice had long since vanished from the rock, and living forms were becoming scarce and stunted.
“It begins to look as though they were ammonia rather than water types,” Carol said thoughtfully, as she threw aside a tangle of filaments that might have been dead roots or a badly designed bird’s nest. “With that disappearing, they aren’t doing very well. Maybe Jenny’s high energy compounds don’t form this deep.”
“You’d think the rivers would carry them at least as far as they themselves flow, if they form on the surface from stellar energy.” Molly was equally pensive. “Ordinary evolution can do a lot, but I suppose it does have its limits. I never heard of a supersonic flyer on any planet, for example. Earth has things that can do with incredibly little water, and these may be the ammonia equivalents; maybe we should sacrifice another of our already collected items and put it in a can.”
Carol hesitated, as Molly had expected. “You’re pretty big. I don’t suppose there’s any space in your armor where you could tuck that thing, is there?”
“Well…” Molly picked it up and considered. “There is room around the removable water and chemical flasks—the ones I bled water from before, for example. Putting foreign matter in there is not exactly good procedure, but the compartments are sealed from the rest of the suit, of course, so I can open them while it’s in use. Maybe—all right. I’ll take a chance. It was my idea about the plants, I’d like to check it out. This thing looks very dry; if a valve leaks and the specimen gets contaminated with water, don’t blame me.”
“Remember the hydrazoic acid!” came Jenny’s voice. Molly hesitated, then reassured herself.
“I’ve already handled this thing pretty roughly. It was growing in soft mud and didn’t take much to pull up, but we dropped it on rock afterward. H-N-three would be liquid at this temperature, so there can’t be enough to matter, anyway.”
“You could have dropped glyceryl nitrate safely on rock in this gravity. Maybe putting that thing in your armor isn’t such a good idea, Molly.” Carol did not actually draw away, but giving danger as much thought as she had just uttered, and allowing the matter to weigh for a moment against the importance of the research, was her equivalent to some people’s screaming and running. Molly was impressed.
Still, she opened the appropriate panel and stowed the tangle away, not entirely without uneasiness. “It’s less likely to get jarred there than in one of the cans, after all,” she said firmly. “Now another temperature check of the water, and we’ll go on.” Carol helped without comment; she had not really expected her big friend to take such a chance, and felt a little guilty. Still, Molly was adult and entitled to take her own risks if she felt the potential gain was worth it; and of course the specimen was worth some risk—why were they here, after all?
It was onward and downward again. For some time the river was just a river; then it fell for long, long minutes from top to bottom of what seemed to be the largest kame yet. The women outraced the drifting drops and found an extensive lake at the bottom. This had a few bits of floating detritus that might or might not have been alive. The edge of the body of water—it was water, according to a quick check—was nowhere in sight, and they set off at random, reaching a cavern wall with no sign of further passages in a few minutes. They followed this around to the left, as had become standard procedure with them, passing half a dozen tunnels but not stopping to investigate until they met one that was serving to drain the lake. They followed the new river without comment.
There was no visible life in or beside it. Its current was slow, though it slanted downward at a steep angle and frequently slithered around rocks that might have fallen into its bed from above. Sometimes there were enough of these to dam it into a pool, whose exit often took several minutes to find in the rubble.
At one of the smaller of these, Molly called for a stop.
“Another temperature check? We did one only a few minutes ago!” Carol’s voice was definitely a complaint.
“Another temperature check. I have my reasons.”
“Which you won’t tell me.”
“Which I’ll show you. Park this thing, please.” Carol stopped the robot, not quite happily, but at least curious.
Molly made a reading, and smiled, invisibly since all the light was concentrated on the instrument. “Three hundred seventeen. It has to be water. There couldn’t be enough ammonia staying with it to smell at that temperature.”
“You’re using it to replace what you used? Why worry? Surely your recycling equipment would handle that sort of impurity.”
“Yes, it would. Probably I should top off my buffer tanks; thanks. I hadn’t thought of that.”
“Then what are you going to do? Drink it? You’d be crazy. You can’t be that tired of reprocessed stuff.”
“I certainly could be, but I’m not yet. Help me get this suit off.”
“You are crazy—oh! Of course.”
“Yes. Of course. Sorry you can’t join me, but you’d parboil in a few seconds.” Molly had undamped her helmet and now removed it carefully, keeping the mask and breathing connections tightly over her nose and mouth. Carol took the helmet and put it down for her, while the Human went to work on the body seals and presently opened and removed the waist-up section. Then she sat down and drew herself carefully out of the walking and recycling part, leaving it sitting on the bank of the pool.