[Transcriber's Note: This etext was produced from
Galaxy Magazine August 1963.
Extensive research did not uncover any evidence that
the U.S. copyright on this publication was renewed.]
Mercury had no atmosphere--everyone knew
that. Why was it developing one now?
I
The wind which had nearly turned the _Albireo's_ landing into a
disaster instead of a mathematical exercise was still playing tunes
about the fins and landing legs as Schlossberg made his way down to
Deck Five.
The noise didn't bother him particularly, though the endless seismic
tremors made him dislike the ladders. But just now he was able to
ignore both. He was curious--though not hopeful.
"Is there anything at all obvious on the last sets of tapes, Joe?"
Mardikian, the geophysicist, shrugged. "Just what you'd expect ... on
a planet which has at least one quake in each fifty-mile-square area
every five minutes. You know yourself we had a nice seismic program set
up, but when we touched down we found we couldn't carry it out. We've
done our best with the natural tremors--incidentally stealing most of
the record tapes the other projects would have used. We have a lot of
nice information for the computers back home; but it will take all of
them to make any sense out of it."
Schlossberg nodded; the words had not been necessary. His astronomical
program had been one of those sabotaged by the transfer of tapes to the
seismic survey.
"I just hoped," he said. "We each have an idea why Mercury developed
an atmosphere during the last few decades, but I guess the high school
kids on Earth will know whether it's right before we do. I'm resigned
to living in a chess-type universe--few and simple rules, but infinite
combinations of them. But it would be nice to know an answer sometime."
"So it would. As a matter of fact, I need to know a couple right now.
From you. How close to finished are the other programs--or what's left
of them?"
"I'm all set," replied Schlossberg. "I have a couple of instruments
still monitoring the sun just in case, but everything in the revised
program is on tape."
"Good. Tom, any use asking you?"
The biologist grimaced. "I've been shown two hundred and sixteen
different samples of rock and dust. I have examined in detail twelve
crystal growths which looked vaguely like vegetation. Nothing was alive
or contained living things by any standards I could conscientiously
set."
Mardikian's gesture might have meant sympathy.
"Camille?"
"I may as well stop now as any time. I'll never be through. Tape didn't
make much difference to me, but I wish I knew what weight of specimens
I could take home."
"Eileen?" Mardikian's glance at the stratigrapher took the place of the
actual question.
"Cam speaks for me, except that I could have used any more tape you
could have spared. What I have is gone."
"All right, that leaves me, the tape-thief. The last spools are in the
seismographs now, and will start running out in seventeen hours. The
tractors will start out on their last rounds in sixteen, and should be
back in roughly a week. Will, does that give you enough to figure the
weights we rockhounds can have on the return trip?"
* * * * *
The _Albireo's_ captain nodded. "Close enough. There really hasn't been
much question since it became evident we'd find nothing for the mass
tanks here. I'll have a really precise check in an hour, but I can
tell right now that you have about one and a half metric tons to split
up among the three of you.
"Ideal departure time is three hundred ten hours away, as you all know.
We can stay here until then, or go into a parking-and-survey orbit at
almost any time before then. You have all the survey you need, I should
think, from the other time. But suit yourselves."
"I'd just as soon be space-sick as seasick," remarked Camille Burkett.
"I still hate to think that the entire planet is as shivery as the spot
we picked."
Willard Rowson smiled. "You researchers told me where to land after ten
days in orbit mapping this rockball. I set you just where you asked. If
you'd found even five tons of juice we could use in the reaction tanks
I could still take you to another one--if you could agree which one. I
hate to say 'Don't blame me,' but I can't think of anything else that
fits."
"So we sit until the last of the tractors is back with the precious
seismo tapes, playing battleship while our back teeth are being
shaken out by earthquakes--excuse the word. What a thrill! Glorious
adventure!" Zaino, the communications specialist who had been out of a
job almost constantly since the landing, spoke sourly. The captain was
the only one who saw fit to answer.
"If you want adventure, you made a mistake exploring space. The only
space adventures I've heard of are second-hand stories built on
guesswork; the people who really had them weren't around to tell about
it. Unless Dr. Marini discovers a set of Mercurian monsters at the last
minute and they invade the ship or cut off one of the tractors, I'm
afraid you'll have to do without adventures." Zaino grimaced.
"That sounds funny coming from a spaceman, Captain. I didn't really
mean adventure, though; all I want is something to do besides betting
whether the next quake will come in one minute or five. I haven't even
had to fix a suit-radio since we touched down. How about my going out
with one of the tractors on this last trip, at least?"
"It's all right with me," replied Rowson, "but Dr. Mardikian runs the
professional part of this operation. I require that Spurr, Trackman,
Hargedon and Aiello go as drivers, since without them even a minor
mechanical problem would be more than an adventure. As I recall it, Dr.
Harmon, Dr. Schlossberg, Dr. Marini and Dr. Mardikian are scheduled to
go; but if any one of them is willing to let you take his or her place,
I certainly don't mind."
The radioman looked around hopefully. The geologists and the biologist
shook their heads negatively, firmly and unanimously; but the
astronomer pondered for a moment. Zaino watched tensely.
"It may be all right," Schlossberg said at last. "What I want to get
is a set of wind, gas pressure, gas temperature and gas composition
measures around the route. I didn't expect to be more meteorologist
than astronomer when we left Earth, and didn't have exactly the right
equipment. Hargedon and Aiello helped me improvise some, and this is
the first chance to use it on Darkside. If you can learn what has to be
done with it before starting time, though, you are welcome to my place."
* * * * *
The communicator got to his feet fast enough to leave the deck in
Mercury's feeble gravity.
"Lead me to it, Doc. I guess I can learn to read a home-made
weathervane!"
"Is that merely bragging, or a challenge?" drawled a voice which had
not previously joined the discussion. Zaino flushed a bit.
"Sorry, Luigi," he said hastily. "I didn't mean it just that way. But I
still think I can run the stuff."
"Likely enough," Aiello replied. "Remember though, it wasn't made just
for talking into." Schlossberg, now on his feet, cut in quickly.
"Come on, Arnie. We'll have to suit up to see the equipment; it's
outside."
He shepherded the radioman to the hatch at one side of the deck and
shooed him down toward the engine and air lock levels. Both were silent
for some moments; but safely out of earshot of Deck Five the younger
man looked up and spoke.
"You needn't push, Doc. I wasn't going to make anything of it. Luigi
was right, and I asked for it." The astronomer slowed a bit in his
descent.
"I wasn't really worried," he replied, "but we have several months yet
before we can get away from each other, and I don't like talk that
could set up grudges. Matter of fact, I'm even a little uneasy about
having the girls along, though I'm no misogynist."
"Girls? They're not--"
"There goes your foot again. Even Harmon is about ten years older than
you, I suppose. But they're girls to me. What's more important, they no
doubt think of themselves as girls."
"Even Dr. Burkett? That is--I mean--"
"Even Dr. Burkett. Here, get into your suit. And maybe you'd better
take out the mike. It'll be enough if you can listen for the next
hour or two." Zaino made no answer, suspecting with some justice that
anything he said would be wrong.
Each made final checks on the other's suit; then they descended
one more level to the airlock. This occupied part of the same deck
as the fusion plants, below the wings and reaction mass tanks but
above the main engine. Its outer door was just barely big enough to
admit a spacesuited person. Even with the low air pressure carried
by spaceships, a large door area meant large total force on jamb,
hinges and locks. It opened onto a small balcony from which a ladder
led to the ground. The two men paused on the balcony to look over the
landscape.
This hadn't changed noticeably since the last time either had been out,
though there might have been some small difference in the volcanic
cones a couple of miles away to the northeast. The furrows down the
sides of these, which looked as though they had been cut by water but
were actually bone-dry ash slides, were always undergoing alteration as
gas from below kept blowing fresh scoria fragments out of the craters.
* * * * *
The spines--steep, jagged fragments of rock which thrust upward from
the plain beyond and to both sides of the cones--seemed dead as ever.
The level surface between the _Albireo_ and the cones was more
interesting. Mardikian and Schlossberg believed it to be a lava sheet
dating from early in Mercury's history, when more volatile substances
still existed in the surface rocks to cut down their viscosity when
molten. They supposed that much--perhaps most--of the surface around
the "twilight" belt had been flooded by this very liquid lava, which
had cooled to a smoother surface than most Earthly lava flows.
How long it had stayed cool they didn't guess. But both men felt sure
that Mercury must have periodic upheavals as heat accumulated inside
it--heat coming not from radioactivity but from tidal energy. Mercury's
orbit is highly eccentric. At perihelion, tidal force tries to pull it
apart along the planet-to-sun line, while at aphelion the tidal force
is less and the little world's own gravity tries to bring it back to
a spherical shape. The real change in form is not great, but a large
force working through even a small amount of distance can mean a good
deal of energy.
If the energy can't leak out--and Mercury's rocks conduct heat no
better than those of Earth--the temperature must rise.
Sooner or later, the men argued, deeply buried rock must fuse to magma.
Its liquefaction would let the bulk of the planet give farther under
tidal stress, so heat would be generated even faster. Eventually a
girdle of magma would have to form far below the crust all around the
twilight strip, where the tidal strain would be greatest. Sooner or
later this would melt its way to the surface, giving the zone a period
of intense volcanic activity and, incidentally, giving the planet a
temporary atmosphere.
The idea was reasonable. It had, the astronomer admitted, been
suggested long before to account for supposed vulcanism on the moon.
It justified the careful examination that Schlossberg and Zaino gave
the plain before they descended the ladder; for it made reasonable
the occasional changes which were observed to occur in the pattern of
cracks weaving over its surface.
No one was certain just how permanent the local surface was--though
no one could really justify feeling safer on board the _Albireo_ than
outside on the lava. If anything really drastic happened, the ship
would be no protection.
The sun, hanging just above the horizon slightly to the watcher's
right, cast long shadows which made the cracks stand out clearly;
as far as either man could see, nothing had changed recently. They
descended the ladder carefully--even the best designed spacesuits are
somewhat vulnerable--and made their way to the spot where the tractors
were parked.
A sheet-metal fence a dozen feet high and four times as long provided
shade, which was more than a luxury this close to the sun. The
tractors were parked in this shadow, and beside and between them were
piles of equipment and specimens. The apparatus Schlossberg had devised
was beside the tractor at the north end of the line, just inside the
shaded area.
It was still just inside the shade when they finished, four hours
later. Hargedon had joined them during the final hour and helped
pack the equipment in the tractor he was to drive. Zaino had had no
trouble in learning to make the observations Schlossberg wanted, and
the youngster was almost unbearably cocky. Schlossberg hoped, as they
returned to the _Albireo_, that no one would murder the communications
expert in the next twelve hours. There would be nothing to worry about
after the trip started; Hargedon was quite able to keep anyone in his
place without being nasty about it. If Zaino had been going with Aiello
or Harmon--but he wasn't, and it was pointless to dream up trouble.
And no trouble developed all by itself.