The Gentle Giants of Ganymede

The pens and animal cages in the Ganymean ship had contained vegetable feed and floor-covering materials that had remained perfectly preserved under the ice coating formed when the ship #146;s atmosphere froze and the moisture condensed out. Using seeds recovered from this material, Danchekker had succeeded in cultivating live plants completely different from anything that had ever grown on Earth, presumed to be examples of native Minervan botany. The leaves were very dark #151;almost black #151;and absorbed every available scrap of sunlight, right across the visible spectrum. This seemed to tie in nicely with independently obtained evidence of Minerva #146;s great distance from the Sun.

'How far,' Rousson asked, 'have we got in figuring out why the Ganymeans were shipping all the animals in?' He spread his arms wide. 'There had to be a reason. How far are we getting on that one? I don #146;t know, but the enzyme might have something to do with it.'

'Very well, let #146;s recapitulate briefly what we think we already know about the subject,' Danchekker suggested. He moved away from the screen and perched on the edge of the table. 'Paul. Would you like to tell us your answer to Henri #146;s question.' Carpenter scratched the back of his head for a second and screwed up his face.

'Well . . .' he began, 'first there #146;s the fish. They #146;re established as being native Minervan and give us our link between Minerva and the Ganymeans.'

'Good,' Danchekker nodded, mellowing somewhat from his earlier crotchety mood. 'Go on.'

Carpenter was referring to a type of well-preserved canned fish that had been positively traced back to its origin in the oceans of Minerva. Danchekker had shown that the skeletons of the fish correlated in general arrangement to the skeletal remains of the Ganymean occupants of the ship that lay under the ice deep below Pithead Base; the relationship was comparable to that existing between the architectures of, say, a man and a mammoth, and demonstrated that the fish and the Ganymeans belonged to the same evolutionary family. Thus if the fish were native to Minerva, the Ganymeans were, too.

'Your computer analysis of the fundamental cell chemistry of the fish,' Carpenter continued, 'suggests an inherent low tolerance to a group of toxins that includes carbon dioxide. I think you also postulated that this basic chemistry could have been inherited from way back in the ancestral line of the fish #151;right from very early on in Minervan history.'

'Quite so,' Danchekker approved. 'What else?'

Carpenter hesitated. 'So Minervan land-dwelling species would have had a low CO2 tolerance as well,' he offered.

'Not quite,' Danchekker answered. 'You #146;ve left out the connecting link to that conclusion. Anybody. . . ? ' He looked at the German. 'Wolfgang?'

'You need to make the assumption that the characteristics of low CO2 tolerance came about in a very remote ancestor #151;one that existed before any land-dwelling types appeared on Minerva.' Fichter paused, then continued. 'Then you can postulate that this remote life form was a common ancestor to all later land dwellers and marine descendants #151;for example, the fish. On the basis of that assumption you can say that the characteristic could have been inherited by all the land-dwelling species that emerged later.'

'Never forget your assumptions,' Danchekker urged. 'Many of the problems in the history of science have stemmed from that simple error. Note one other thing too: If the low-C02 -tolerance characteristic did indeed come about very early in the process of Minervan evolution and survived right down to the time that the fish was alive, then suggestions are that it was a very stable characteristic, if our knowledge of terrestrial evolution is anything to go by anyway. This adds plausibility to the suggestion that it could have become a common characteristic that spread throughout all the land dwellers as they evolved and diverged, and has remained essentially unaltered down through the ages #151;much as the basic design of terrestrial vertebrates has remained unchanged for hundreds of millions of years despite superficial differences in shape, size and form.' Danchekker removed his spectacles and began polishing the lenses with his handkerchief.

'Very well,' he said. 'Let us pursue the assumption and conclude that by the time the Ganymeans had evolved #151;twenty-five million years ago #151;the land surface of Minerva was populated by a multitude of its own native life forms, each of which possessed a low tolerance to carbon dioxide, among other things. What other clues do we have available to us that might help determine what was happening on Minerva at that time?'

'We know that the Ganymeans were quitting the planet and trying to migrate someplace else,' Sandy Holmes threw in. 'Probably to some other star system.'

'Oh, really?' Danchekker smiled, showing his teeth briefly before breathing on his spectacle lenses once more. 'How do we know that?'

'Well, there #146;s the ship down under the ice here for a start,' she replied. 'The kind of freight it was carrying and the amount of it sure suggested a colony ship intending a one-way trip. And then, why should it show up on Ganymede of all places? It couldn #146;t have been traveling between any of the inner planets, could it?'

'But there #146;s nothing outside Minerva #146;s orbit to colonize,' Carpenter chipped in. 'Not until you get to the stars, that is.'

'Exactly so,' Danchekker said soberly, directing his words at the woman. 'You said #145;suggested a colony ship. #146; Don #146;t forget that that is precisely what the evidence we have at present amounts to #151;a suggestion and nothing more. It doesn #146;t prove anything. Lots of people around the base are saying we now know that the Ganymeans abandoned the Solar System to find a new home elsewhere because the carbon-dioxide concentration in the Minervan atmosphere was increasing for some reason which we have yet to determine. It is true that if what we have just said was fact, then the Ganymeans would have shared the low tolerance possessed by all land dwellers there, and any increase in the atmospheric concentration could have caused them serious problems. But as we have just seen, we know nothing of the kind; we merely observe one or two suggestions that might add up to such an explanation.' The professor paused, seeing that Carpenter was about to say something.

'There was more to it than that though, wasn #146;t there?' Carpenter queried. 'We #146;re pretty certain that all species of Minervan land dwellers died out pretty rapidly somewhere around twenty-five million years ago . . . all except the Ganymeans themselves maybe. That sounds like just the effect you #146;d expect if the concentration did rise and all the species there couldn #146;t handle it. It seems to support the hypothesis pretty well.'

'I think Paul #146;s got a point,' Sandy Holmes chimed in. 'Everything adds up. Also, it fits in with the ideas we #146;ve been having about why the Ganymeans were shipping all the animals into Minerva.' She turned toward Carpenter, as if inviting him to complete the story from there.

As usual, Carpenter didn #146;t need much encouragement. 'What the Ganymeans were really trying to do was redress the CO2 imbalance by covering the planet with carbon-dioxide-absorbing, oxygen-producing terrestrial green plants. The animals were brought along to provide a balanced ecology that the plants could survive in. Like Sandy says, it all fits.'

'You #146;re trying to fit the evidence to suit the answers that you already want to prove,' Danchekker cautioned. 'Let #146;s separate once more the evidence that is fact from the evidence which is supposition or mere suggestion.' The discussion continued with Danchekker leading an examination of the principles of scientific deduction and the techniques of logical analysis. Throughout, the figure who had been following the proceedings silently from his seat at the end of the table farthest from the screen continued to draw leisurely on his cigarette, taking in every detail.

Dr. Victor Hunt had also accompanied the team of scientists who had come with Jupiter Five more than three months before to study the Ganymean ship. Although nothing truly spectacular had emerged during this time, huge volumes of data on the structure, design and contents of the alien ship had been amassed. Every day, newly removed devices and machinery were examined in the laboratories of the surface bases and in the orbiting J4 and J5 mission command ships. Findings from these tests were as yet fragmentary, but clues were beginning to emerge from which a meaningful picture of the Ganymean civilization and the mysterious events of twenty-five million years before might eventually emerge.

That was Hunt #146;s job. Originally a theoretical physicist specializing in mathematical nucleonics, he had