various atmospheric gases and volcanically introduced water vapor,
that is consistent with known data. To s’ustain the levels of free
atmospheric carbon dioxide and water vapor, and the existence of
large amounts of water in a liquid state, the model requires a very
high level of volcanic activity on the planet, at least in its
earlier history. That this requirement was evidently met could
suggest that relative to its size, the crust of Minerva was
exceptionally thin, and the structure of this crust unstable. This
is significant, as becomes clear later. Fuller’s model also ties in
with the latest information from the Asteroid surveys. The thin
crust could be the result of relatively rapid surface cooling
caused by the vast distance from the Sun, but with the internal
molten condition being prolonged by heat sources below the surface.
The Asteroid missions report many samples being tested that are
rich in radioactive heat-producing substances.
“So, Minerva cooled to a mean surface temperature somewhat colder
than Earth’s but not as cold as you might think. With cooling came
the formation of increasingly more complex molecules, and
eventually life emerged. With life came diversification, followed
by competition, followed by selection-in other words, evolution.
After many millions of years, evolution culminated in a race of
intelligent beings who became dominant on the planet These were the
beings we have christened the Ganymeans.
“The Ganymeans developed an advanced technological civilization.
Then, approximately twenty-five million years ago, they had reached
a stage which we estimate to be about a hundred years ahead of our
own. This estimate is based on the design of the Ganymean ship
we’ve been looking at here, and the equipment found inside it.
“Some time around this period, a major crisis developed on Minerva.
Something upset the delicate mechanism controlling the balance
between the amount of carbon dioxide locked up in the rocks and
that in the free state; the amount in the atmosphere began to rise.
The reasons for this are speculative. One possibility is that
something triggered the tendency toward high volcanic activity
inherent in Minerva’s structure-maybe natural causes, maybe
something the Ganymeans did. Another possibility is that the
Ganymeans were attempting an ambitious program of climate control
and the whole thing went wrong in a big way. At present we
really don’t have a good answer to this part. However, our
investigations of the Ganymeans have hardly begun yet. There are
still years of work to be done on the contents of the ship alone,
and I’m pretty certain that there’s a lot more waiting to be
discovered down under the ice here.
“Anyhow, the main point for the present is that something happened.
Chris Danchekker has shown . . .” Another file reference appeared
on the bottom of the screen. “. . . that all the higher,
air-breathing Minervan life forms would almost certainly have
possessed a very low tolerance to increases in carbon-dioxide
concentration. This derives from the fundamental system of
microchemistry inherited from the earliest ancestors of the line.
This implies, of course, that the changing surface conditions on
Minerva posed a threat to the very existence of most forms of land
life, including the Ganymeans. If we accept this situation, we also
have a plausible reason for supposing that the Ganymeans went
through a phase of importing on a vast scale a mixed balance of
plant and animal life from Earth. Perhaps, stuck out where it was,
Minerva had nothing to compare with the quantity and variety of
life teeming on the much warmer planet Earth.
“Evidently, the experiment didn’t work. Although the imported stock
found conditions favorable enough to flourish in, they failed to
produce the desired result. From various bits of information, we
believe the Ganymeans gave the whole thing up as a bad job and
moved out to find a new home somewhere outside the Solar System.
Whether or not they succeeded we don’t know; maybe further study of
what’s in the ship will throw more light on that question.”
Hunt stopped to pick up a case from the desk and went through the
motions of lighting a cigarette. The break seemed to be timed to
give the viewers a chance to digest this part of his narrative. A