If Hargedon saw this, he said nothing. He set Zaino to picking up every other instrument, as any partner would have, making no allowance for the work the youngster was doing for Schlossberg. This might, of course, have had the purpose of keeping the radioman too busy to think about discomfort. Or it might merely have been Hargedon’s idea of normal procedure.
Whatever the cause, Zaino got little chance to use the radio once they had driven into the darkness. He managed only one or two brief talks with those left at the ship.
The talks might have helped his morale, since they certainly must have given the impression that nothing was going on in the ship while at least he had something to do in the tractor. However, this state of affairs did not last. Before the vehicle was four hours out of sight of the Albireo, a broadcast by Camille Burkett reached them.
The mineralogist’s voice contained at least as much professional enthusiasm as alarm, but everyone listening must have thought promptly of the dubious stability of Mercury’s crust. The call was intended for her fellow geologists Mardikian and Harmon. But it interested Zaino at least as much.
“Joe! Eileen! There’s a column of what looks like black smoke rising over Northeast Spur. It can’t be a real fire, of course; I can’t see its point of origin, but if it’s the convection current it seems to me the source must be pretty hot. It’s the closest thing to a genuine volcano I’ve seen since we arrived; it’s certainly not another of those ash mounds. I should think you’d still be close enough to make it out, Joe. Can you see anything?”
The reply from Mardikian’s tractor was inaudible to Zaino and Hargedon, but Burkett’s answer made its general tenor plain.
“I hadn’t thought of that. Yes, I’d say it was pretty close to the Brightside route. It wouldn’t be practical for you to stop your run now to come back to see. You couldn’t do much about it anyway. I could go out to have a look and then report to you. If the way back is blocked there’ll be plenty of time to work out another.” Hargedon and Zaino passed questioning glances at each other during the shorter pause that followed.
“I know there aren’t,” the voice then went on, responding to the words they could not hear, “but it’s only two or three miles, I’d say. Two to the spur and not much farther to where I could see the other side. Enough of the way is in shade so I could make it in a suit easily enough. I can’t see calling back either of the Darkside tractors. Their work is just as important as the rest — anyway, Eileen is probably out of range. She hasn’t answered yet.”
Another pause.
“That’s true. Still, it would mean sacrificing that set of seismic records — no, wait. We could go out later for those. And Mel could take his own weather measures on the later trip. There’s plenty of time!”
Pause, longer this time.
“You’re right, of course. I just wanted to get an early look at this volcano, if it is one. We’ll let the others finish their runs, and when you get back you can check the thing from the other side yourself. If it is blocking your way there’s time to find an alternate route. We could be doing that from the maps in the meantime, just in case.”
Zaino looked at his companion.
“Isn’t that just my luck!” he exclaimed. “I jump at the first chance to get away from being bored to death. The minute I’m safely away, the only interesting thing of the whole operation happens — back at the ship!”
“Who asked to come on this trip?”
“Oh, I’m not blaming anyone but myself. If I’d stayed back there the volcano would have popped out here somewhere, or else waited until we were gone.”
“If it is a volcano. Dr. Burkett didn’t seem quite sure.” “No, and I’ll bet a nickel she’s suiting up right now to go out and see. I hope she comes back with something while we’re still near enough to hear about it.”
Hargedon shrugged. “I suppose it was also just your luck that sent you on a Darkside trip? You know the radio stuff. You knew we couldn’t reach as far this way with the radios. Didn’t you think of that in advance?”
“I didn’t think of it, any more than you would have. It was bad luck, but I’m not grousing about it. Let’s get on with this job.” Hargedon nodded with approval, and possibly with some surprise, and the tractor hummed on its way.
The darkness deepened around the patches of lava shown by the driving lights; the sky darkened toward a midnight hue, with stars showing ever brighter through it; and radio reception from the Albireo began to get spotty. Gas density at the low ion layer was high enough so that recombination of molecules with their radiation-freed electrons was rapid. Only occasional streamers of ionized gas reached far over Darkside. As these thinned out, so did radio reception. Camille Burkett’s next broadcast came through very poorly.
There was enough in it, however, to seize the attention of the two men in the tractor.
She was saying: “—real all right, and dangerous. It’s the. . thing I ever saw. . kinds of lava from what looks like. . same vent. There’s high viscosity stuff building a spatter cone to end all spatter cones, and some very thin fluid from somewhere at the bottom. The flow has already blocked the valley used by the Brightside routes and is coming along it. A new return route will have to be found for the tractors that. . was spreading fast when I saw it. I can’t tell how much will come. But unless it stops there’s nothing at all to keep the flow away from, the ship. It isn’t coming fast, but it’s coming. I’d advise all tractors to turn back. Captain Rowson reminds me that only one takeoff is possible. If we leave this site, we’re committed to leaving Mercury. Arnie and Ren, do you hear me?”
Zaino responded at once. “We got most of it, Doctor. Do you really think the ship is in danger?”
“I don’t know. I can only say that if this flow continues the ship will have to leave, because this area will sooner or later be covered. I can’t guess how likely. . check further to get some sort of estimate. It’s different from any Earthly lava source — maybe you heard — should try to get Eileen and Eric back, too. I can’t raise them. I suppose they’re well out from under the ion layer by now. Maybe you’re close enough to them to catch them with diffracted waves. Try, anyway. Whether you can raise them or not you’d better start back yourself.”
Hargedon cut in at this point. “What does Dr. Mardikian say about that? We still have most of the seismometers on this route to visit.”
“I think Captain Rowson has the deciding word here, but if it helps your decision Dr. Mardikian has already started back. He hasn’t finished his route, either. So hop back here, Ren. And Arnie, put that technical skill you haven’t had to use yet to work raising Eileen and Eric.”
“What I can do, I will,” replied Zaino, “but you’d better tape a recall message and keep it going out on — let’s see band F.”
“All right. be ready to check the volcano as soon as you get back. How long?”
“Seven hours — maybe six and a half,” replied Hargedon. “We have to be careful.”
“Very well. Stay outside when you arrive; I’ll want to go right out in the tractor to get a closer look.” She cut off.
“And that came through clearly enough!” remarked Hargedon as he swung the tractor around. “I’ve been awake for fourteen hours, driving off and on for ten of them. I’m about to drive for another six; and then I’m to stand by for more.”