Chapter 17

Preliminary analysis of the specimens produced a strangely mixed bag of results. The air, as the Argo had found, was quite breathable without respiratory filters; it was considerably more pollen-laden than Earth's—an ecology without significant insect population would naturally rely more heavily on airborne dissemination—but the pollens were completely innocuous to humans. Likewise the water was perfectly drinkable; the natural sediments would simply pass through the human digestive tract without effect.

"But these things lead me to a further, perhaps less happy point," said Heisinger at a general meeting called to report on the results. "The local flora and fauna are likewise biologically inert to Earth creatures. It appears that the development of life on Eden proceeded along completely different lines than ours."

"Can you spell that out?" called a voice from the floor.

"We can eat anything we want here. I don't know, some of it might even taste all right, although I suspect it would seem pretty bland. But there's no nutrition in it for us at all. Even Earth vegetation won't grow here, the chemical structure's all wrong"

"Does that hold true reciprocally?" Igwanda asked.

"Both ways; they can't eat Earth food either. Or us, if you're concerned about carnivores, Colonel. Eden animals likely can't even scent us, for that matter. Biochemically the two worlds are completely incompatible.

"I'll give you all an example. Virtually all Earth plants rely on photosynthesis, of course—light, whether solar or artificial, is absorbed to drive the biosystem. Here the equally universal mechanism is thermosynthesis; they use heat instead of light. That accounts for the much greater level of underbrush in forested areas, and probably also for the fact that the Centerville crops continue to thrive under that appalling blanket of smog generated by the ironworks."

"But why is Eden so green, then?" asked Toshimura from the floor. "I thought plants were green from chlorophyll?"

"At home they are," Heisinger responded. "Here there is of course no chlorophyll, which is the photosynthetic agent. So far as Wanda and I have been able to determine, it's mere coincidence that the thermophyll, as we're calling the heat conversion chemical, also profuses the vegetation green."

"Some coincidence. But what about the animals?"

"We benefitted there by having several very fresh cadavers with which to work," said Heisinger, shooting Igwanda a glance. "They're all of one species, which limits our ability to generalize, but they're of generically similar appearance to others we saw, and dissection shows basically the same internal structure as with the other less complete carcasses we retrieved."

He described the unusual method of waste elimination—microscopic examination had shown that the "sweat" was indeed that—and how indigestible solids were regurgitated. "There aren't many such solids, however," he added. "The digestive tracts are extraordinarily sturdy by Earth standards, with musculature exerting physical pressure in addition to quite powerful enzymatic breakdown.

"Once the extraction of nutrients is complete—it's considerably more efficient than ours, so they likely require less frequent meals—what remains is processed through an organ somewhat similar in function, though not in action, to our kidneys. There's a subcutaneous distribution network perhaps analogous to our lymphatic system. Output is suffused throughout that network and then excreted through pores in the hides which are apparently subject to volitional control; the creatures can open or close them more or less at will.