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out, escalated, and got out of control. Both the previous
objections carried less weight when viewed in this context; in the
end, this explanation was accepted as possible. That left only one
other possibility: some kind of chemical change in the Minervan
atmosphere to which the native species hadn't been capable of
adapting but the terrestoids had. But what?
While the pros and cons of these alternatives were still being
evaluated on Jupiter Five, the laser link to Earth brought details
of a new row that had broken out in Navcomms. A faction of Pure
Earthists had produced calculations showing that the Lunarians
could never have survived on Minerva at all, let alone flourished
there; at that distance from the Sun it would simply have been too
cold. They also insisted that water could never have existed on the
surface in a liquid state and held this fact as proof that wherever
the world shown on Charlie's maps had been, it couldn't have been
anywhere near the Asteroids.
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Against this attack the various camps of Minerva-ists concluded
a hasty alliance and opened counterfire with calculations of their
own, which invoked the greenhouse effect of atmospheric carbon
dioxide to show that a substantially higher temperature could have
been sustained. They demonstrated further that the percentage of
carbon dioxide required to produce the mean temperature that they
had already estimated by other means, was precisely the figure
arrived at by Professor Schorn in his deduction of the composition
of the Minervan atmosphere from an analysis of Charlie's cell
metabolism and respiratory system. The land mine that finally
demolished the Pure Earthist position was Schom's later
pronouncement that Charlie exhibited several physiological signs
implying adaptation to an abnormally high level of carbon dioxide.
Their curiosity stimulated by all this sudden interest in the
amount of carbon dioxide in the Minervan atmosphere, Hunt and
Danchekker devised a separate experiment of their own. Combining
Hunt's mathematical skill with Danchekker's knowledge of
quantitative molecular biology, they developed a computer model of
generalized Minervan microchemical behavior potentials, based on
data derived from the native fish. It took them over three months
to perfect. Then they applied to the model a series of mathematical
operators that simulated the effects of different chemical agents
in the environment. When he viewed the results on the screen in one
of the console rooms Danchekker's conclusion was quite definite:
"Any air-breathing life form that evolved from the same primitive
ancestors as this fish and inherited the same fundamental system of
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microchemistry, would be extremely susceptible to a family of
toxins that includes carbon dioxide-far more so than the majority
of terrestrial species."
For once, everything added up. About twenty-five million years ago,
the concentration of carbon dioxide in the atmosphere of Minerva
apparently increased suddenly, possibly through some natural cause
that had liberated the gas from chemical combination in rocks, or
possibly as a result of something the Ganymeans had done. This
could also explain why the Ganymeans had brought in all the
animals. Perhaps their prime objective had been to redress the
balance by covering the planet with carbon-dioxideabsorbing,
oxygen-producing terrestrial green plants; the animals had been
included simply to preserve a balanced ecology in which the plants
could survive. The attempt failed. The native life succumbed, and
the more highly resistant immigrants flourished and
spread out over a whole new world denuded of alien competition.
Nobody knew for sure that it had been so on Minerva. Possibly
nobody ever would.
And nobody knew what had become of the Ganymeans. Perhaps they had
perished along with their cousins. Perhaps, when their efforts
proved futile, they had abandoned Minerva to its new inhabitants
and left the Solar System completely to find a new home elsewhere.
Hunt hoped so. For some strange reason he had developed an
inexplicable affection for this mysterious race. In one of the
Lunarian texts he had come across a verse that began: "Far away
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among the stars, where the Giants of old now live. . ." He hoped it
was true. [ Pobierz całość w formacie PDF ]