“Assuming, of course, that the boat gets us back to the tent to work over our data—or is that inconsistent with a favorite hypothesis?”
“Are you worried?” asked Charley. The Shervah turned her head so that both her side-placed eyes could cover the speaker at once; then she rolled them both away from him in opposite directions.
“No.” The eye that had come to rest covering Molly winked. The Human wondered what that could mean; her translator had no way of handling gestures. Even with a private channel available, she decided, this was not a good lime to ask. She glanced toward Joe.
“All that I need there is on the boat,” Joe responded.
“Your robots, too? Everybody else ready to go?”
“One drifter and its slaves are in the tent. I’ll set them out when we get back. I’m ready, yes.” The others spoke or gestured agreement, and Molly keyed the boat off the surface.
Even without the wind, there was still precipitate; visibility in short waves—short enough for Molly—was only a kilometer or two. This was not dangerous, since the radar maps had shown very little relief on the planet’s surface and they were flying high enough to clear all of this, but it was boring. Molly shifted her pickup farther into the infrared, converting it at the screen to light that she could see but that was not short enough in wavelength to bother the others. It would have been possible to hood the screen and keep her face buried in it, but with only her own personal friends present she preferred to feel free to look around. The others, she saw, were also examining the surface flowing past below them. Not real work, by Joe’s standards.
So far there was no sign of liquid, in spite of Jenny’s pressure report; they might have been over Enigma’s Arabian Desert. Dunes, easily recognized from above by their crescent shape, were numerous when they started, but before reaching the first vertex of Joe’s imaginary dodecahedron, the sand gave way to what looked more like bare rock. Molly was tempted to land for a sample, but decided against it; she would be busy enough with the scheduled stops, and more specimens could always be obtained if needed. She did not like to display impatience, especially before Joe. She knew he would understand, but didn’t want him to have to.
The boat announced the approach to the first site, and a few seconds later came to a halt a few hundred meters above the ground. The five spent only seconds examining the surface, which was not very impressive: bare rock, very smooth on the finer scale, rippled and hummocked with larger irregularities averaging a few dozen meters across and one or two in height. Nothing showed any sign that liquid had ever flowed there, but the surface might well have been polished by wind-blown sand. Without waiting for suggestions from anyone else, Molly keyed the boat to slow descent. It settled to the rock half a minute later.
Joe had already resumed his armor and was out of the conning room before they were down. Carol went with him. Three minutes later the robot—much taller than the one the Shervah had ridden to Joe’s rescue, since its slaves were now riding its top—was standing on the polished stone. Charley was outside cutting samples from the hard parts of the surface and scooping up bits of loose material that were lying in smaller hollows. Each went into a separate container, carefully labeled, and Molly recorded the whole procedure visually from on board. Carol was back inside before the Kantrick had finished, but Joe remained beside his machine, fussing with its various controls, until everything else scheduled for the site had been done.
By the tenth landing, everything was both routine and, for some of the students, boring. Twice they had put down on lakes. Sampling was more interesting there; Jenny had gladly submerged and obtained liquid, solid, and mud specimens. Any of them could have done the same, as their armor was quite adequate for such an environment, but she was the only one used to a liquid environment, and the others felt the usual discomfort at not being able to see normally below the surface. Even Jenny was a little unhappy at so much clear liquid; she was used to the tangled vegetation of the swamps of Hrimm, where the combination of climbing and swimming for which her form was so well suited was the standard way to get around.
The twelfth stop was desert again, this time with little evidence of wind. They were on the night side of Enigma now. As they descended, Molly wondered whether really different material would ever turn up. She was getting a little puzzled; the overall size and gravity of the world had matched her comet hypothesis, as had the atmosphere, but the specimens collected so far had not.
The planet’s average density, from size and gravity, was about five thirds that of water, which by any reasonable standards suggested that a good deal of its makeup was ice—water, ammonia, carbon dioxide, or methane. The atmosphere strongly supported this notion, but the rocks, at nearly twice the planet’s average density, did not. Molly, very prematurely—before coming within sight of the place, in fact—had convinced herself and Charley that Enigma was simply a young ice-and-silicate body that any decently programmed translator would call a comet, but which was far too big and had far too high an escape velocity to show a tail even in Arc’s impressive stellar wind.
The ice, it was beginning to appear, was already largely gone from much of the surface; it looked as though she would have to drill for it, and she had not come prepared to do any such thing.
This was embarrassing. She had been given laboratory assignments at School obviously intended to remind her of the need to be prepared for the unexpected. Worse, her present companions had taken the assignments with her. Worse yet, she had done well on them, receiving even Joe’s commendation on the way she had gotten the group out of trouble when it had looked for a time as though they had done a prematurely destructive test on a problem sample.
The present situation was not only embarrassing but hard to believe. She had encountered plenty of ice bodies, small and large. There had been comets; there had been Pluto and Titan and Callisto in the Solar system, and Think and Sink in the School one. She knew what ice could do, given a set of temperature and pressure parameters.
If it were all buried, it could not be contributing very rapidly to the atmosphere, and the latter had no business being anything like as dense as it was. At cloud-top temperature, methane and ammonia would escape in a few decades at the outside, even without bothering to consider Arc’s ultraviolet and the still faster loss of free hydrogen. The Human did not really enjoy mathematical modeling, but it looked as though she were going to have to play at it.
After the present supply of data had been gathered and organized, of course. There might be easier explanations.
“We’re coming down in a crater.” Joe’s quiet tones cut into Molly’s cogitation. Her fingers moved on the keys.
“There don’t seem to be any real craters here,” objected Jenny. “Nothing suggesting them showed on the radar maps.”
“Nothing suggesting impact features,” admitted Joe. “The hole we are just avoiding would look volcanic except that there is very little buildup around its edge, and the bottom is well below the surrounding ground level. There were many such on both the original map and the one we made during approach. If they had been mentioned in the original description we had of Enigma, we would certainly have been expected to offer an explanation for them.”
“Shouldn’t we anyway?” asked Jenny.
“If you can think of one, and the requisite work doesn’t interfere too greatly with what is already planned. Allowing oneself to become distracted by the unexpected is one of the more certain ways to keep from finishing any task, it seems to me.”