Hal Clement - Still River

“Wait. Don’t start back yet; we’ll try to think of something else.”

“I wasn’t going to. I’m awfully tired.”

“All right, rest. We have some work here and will be back with you soon.”

But Carol did not rest. She drove the robot slowly and carefully twice around the perimeter of the cavern, a few meters above the surface of the mud. Not finding what she wanted, she repeated the maneuver fifteen meters higher. This time she located four openings that might conceivably lead to additional tunnels. Explaining to Molly what she was doing, she parked the robot at the mouth of each in turn and explored it briefly by herself. She was not exactly on foot, though her status was not yet quite free fall.

Two of the passages seemed to go on indefinitely; she followed each for a hundred meters or so before returning. One of the others went horizontally for some fifteen meters and reached a dead end, the barrier closing it formed apparently of hardened mud. The last of the four slanted sharply downward and also came to an early end, but for some reason was entirely free of sediment.

Carol sternly suppressed the urge to stop everything and try to figure out how this could have happened; she did not even look for small drains or wind vents. After some thought she brought the robot to the mouth of the last passage, helped Molly untie herself, and guided her inside. For the moment she left the machine at its mouth.

“Stay here, and sleep if you can,” she said briefly. “I have something to try out. I’ll be back soon. Call if you’re worried; I won’t be far.”

“All right.” Molly did not like to ask for details; her work and friendship with Joe had instilled a good deal of the Nethneen courtesy code into her. In any case, she was quite willing to sleep. Nothing could happen while they weren’t traveling, of course.

The Shervah half floated, half walked out toward the center of the cavern. The mud floor, pierced with the wind vents that repeatedly tried to pick her up when fatigue made her careless, was nearly three kilometers across. Again she was tempted to stop to figure out the feedback mechanism that must have existed to cause the vents to form so uniformly. Something to do with drying rates? The way in which the liquid returned—no, Carol. Stick to business.

The nearly nonexistent gravity both helped and threatened to spoil her plan. She had a digging tool of sorts: her sampling hammer, an ordinary geological pick. She approached one of the vents, as nearly at the cavern center as she could judge, and began swinging.

Her cut was a nearly circular groove over a meter across, wide enough for her small hands to work to some depth. She was hoping that the surface of the mud would be harder than that lower down, and was relieved to find that this was the case. When she thought the groove was deep enough, she worked both hands and the hammer down one side and pried.

A small part of the edge cracked out, giving her a fragment of hardened mud massing perhaps five or six kilograms. This was not what she wanted, and she tried again, digging deeper before she pried. This time the entire circle lifted, though it broke in two before she had it quite out where she wanted it. She accepted that. There was one more test.

She carried one of the pieces over to the nearby vent and used it as a cap, circulation overspeeding and breathing stopped as she waited to see whether the wind would lift it against the feeble gravity.

It stayed. She gave her grotesque equivalent of a smile and began digging again.

Three and a half hours later, nearly exhausted, she had twenty-five of the mud caps or reasonably large fragments of mud caps each lying beside a vent.

She swept her light around to make sure she knew the direction to the robot and Molly, and began placing the caps, one after another, as quickly as she could, over wind vents. In ten minutes or less, there was an area at the center of the cave free of updraft, and a quick glance upward warned her that gravity was doing what she had hoped. The drops—School grant they were peroxide, but she hadn’t dared make the obvious test—were settling in the center. She got out of their way quickly, but stopped near the edge of the plugged area to watch the results of her work in detail.

Her tiny fists clenched as the first of the blobs of liquid touched the warm mud. It stuck, and began to soak in, and slowly she relaxed. More drops were coming, and slowly she retreated toward the robot and her blinded friend.

Long before she got there, the supply of liquid was exceeding the capillary capacity of the mud, but hydrogen bonding was doing its work. The drops that touched the surface, or touched other drops on the surface, stuck, and a growing, pulsing dome of liquid was swelling where the wind had been stopped.

Satisfied, Carol made her way back to the side cave in a few careful leaps.

“All right, Molly? Get any sleep?”

“Some. What have you been up to?”

“You’ll see in a moment.”

“See?”

“Quite possibly. Joe, you still there?” “Yes. Jenny has not reached the hollow yet.” “All right. Your computer is set to detect any change in the surface, didn’t you say?” “Yes.”

“Your mappers are covering as much of the polar mud cap as possible?” “Yes.”

“All right. I’m going to give a quick countdown. At zero, start timing and start watching your model for changes. There may be more than one, and at more than one time, so if you see something don’t stop watching. Are you ready?”

“Yes.”

“All right, give me a few seconds to get our machine as far inside this hole as possible. That isn’t very far, but we may need the shelter. There. Where’s my light? I can sic the liquid—yes, clearly enough. Here comes the count. Four. Three. Two. One. Zero.” Carol’s testing laser unloaded.

Even Molly saw the flash through her closed lids and from deep in the tunnel. The ground shock took over a second to reach them and was not very energetic; the mud, as Carol had hoped, transmitted the wave very poorly. The sound, arriving slightly later, was much worse, but their armor held.

“I took a seismology course once,” the Shervah remarked complacently. “How about it, Joe?” There was a pause.

“Most of the mud cap is moving. The area is spreading out…”

“Gravdh! Did you spot where it started?”

“Oh, yes. About forty-five kilometers northwest of where Charley emerged. You couldn’t have been on the same river, I guess. And now there’s more. Four sites near the starting point are changing further—there is material erupting from several of the tunnel mouths.”

“I hadn’t counted on that. I suppose there was enough mud knocked loose all the way along the tunnels to supply the material, but I didn’t expect it to travel far upwind. It couldn’t have. Surely it’s already blowing back toward the tunnels?” Again there was a pause.

“Yes, it seems to be.”

“All right. Actually, that’s very lucky. I was expecting the seismic jolt would zero the area where you could resume your mapping with a really good chance of meeting us, but I didn’t think there was going to be quite such a perfect guide to where we are. It’s just as well. I’m afraid our robot is out of action from the blast wave; you’ll have to come and get us. Just follow any of the four passages that erupted, and don’t worry about getting buried. There can’t be anything left in them that your mapper could possibly knock loose. We’ll be waiting for you out in the open, once we’ve gotten around the remains of this machine. It’s kind of jammed into our shelter, but your radar should spot it all right. Be sure you map the route, so Jenny can follow you if she has to. She shouldn’t, of course, but ...”