Zaino was not only still alive but still reasonably popular when
the first of the tractors set out, carrying Eileen Harmon and Eric
Trackman, the _Albireo's_ nuclear engineer.
It started more than an hour before the others, since the
stratigrapher's drilling program, "done" or not, took extra time. The
tractor hummed off to the south, since both Darkside routes required a
long detour to pass the chasm to the west. Routes had been worked out
from the stereo-photos taken during the orbital survey. Even Darkside
had been covered fairly well with Uniquantum film under Venus light.
The Harmon-Trackman vehicle was well out of sight when Mardikian and
Aiello started out on one of the Brightside routes, and a few minutes
later Marini set out on the other with the spacesuit technician, Mary
Spurr, driving.
Both vehicles disappeared quickly into a valley to the northeast,
between the ash cones and a thousand-foot spine which rose just south
of them. All the tractors were in good radio contact; Zaino made sure
of that before he abandoned the radio watch to Rowson, suited up and
joined Hargedon at the remaining one. They climbed in, and Hargedon set
it in motion.
At about the same time, the first tractor came into view again, now
traveling north on the farther side of the chasm. Hargedon took this as
evidence that the route thus far was unchanged, and kicked in highest
speed.
The cabin was pretty cramped, even though some of the equipment had
been attached outside. The men could not expect much comfort for the
next week.
Hargedon was used to the trips, however. He disapproved on principle
of people who complained about minor inconveniences such as having
to sleep in spacesuits; fortunately, Zaino's interest and excitement
overrode any thought he might have had about discomfort.
This lasted through the time they spent doubling the vast crack in
Mercury's crust, driving on a little to the north of the ship on the
other side and then turning west toward the dark hemisphere. The
route was identical to that of Harmon's machine for some time, though
no trace of its passage showed on the hard surface. Then Hargedon
angled off toward the southwest. He had driven this run often enough
to know it well even without the markers which had been set out with
the seismographs. The photographic maps were also aboard. With them,
even Zaino had no trouble keeping track of their progress while they
remained in sunlight.
However, the sun sank as they traveled west. In two hours its lower rim
would have been on the horizon, had they been able to see the horizon;
as it was, more of the "sea level" lava plain was in shadow than not
even near the ship, and their route now lay in semi-darkness.
The light came from peaks projecting into the sunlight, from scattered
sky-light which was growing rapidly fainter and from the brighter
celestial objects such as Earth. Even with the tractor's lights it was
getting harder to spot crevasses and seismometer markers. Zaino quickly
found the fun wearing off ... though his pride made him cover this fact
as best he could.
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
be 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 dark-side 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 again 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 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. I'll 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."
"Would you like me to do some of the driving?" asked Zaino.
"I guess you'll have to, whether I like it or not," was the rather
lukewarm reply. "I'll keep on for awhile, though--until we're back in
better light. You get at your radio job."