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
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
among the stars, where the Giants of old now live. . .” He hoped it
was true.
And so, quite suddenly, at least one chapter in the early history
of Minerva had been cleared up. Everything now pointed to the
Lunarians and their civilization as having developed on Minerva and
not on Earth. It explained the failure of Schorn’s early attempt to
fix the length of the day in Hunt’s calendar by calculating
Charlie’s natural periods of sleep and wakefulness. The ancestors
of the Lunarians had arrived from Earth carrying a deeply rooted
metabolic rhythm evolved around a twenty-four-hour cycle. During
the twenty-five million years that followed, some of the more
flexible biological processes in their descendants adapted
successfully to the thirty-five-hour day of Minerva, while others
changed only partially. By Charlie’s time, all the Lunarians’
physiological clocks had gotten hopelessly out of synchronization;
no wonder Schorn’s results made no sense. But the puzzling numbers
in Charlie’s notebook still remained to be accounted for.
In Houston, Caldwell read Hunt and Danchekker’s joint report with
deep satisfaction. He had realized long before that to achieve
results, the abilities of the two scientists would have to be
combined and focused on the problem at hand instead of being
dissipated fruitlessly in the friction of personal incompatibility.
How could he manipulate into being a situation in which the things
they had in common outweighed their differences? Well, what did
they have in common? Starting with the simplest and most obvious
thing-they were both human beings from planet Earth. So where would
this fundamental truth come to totally overshadow anything else?