The landscape was a featureless, undulating sheet of ice that extended in every direction to merge into the gloom of a perpetual night. Overhead a diminutive Sun, barely more than just a bright star among millions, sent down its feeble rays to paint an eerie and foreboding twilight on the scene.

The huge shadowy shape of the ship soared upward to lose itself in the blackness above; arc lights set high on its side cast down a brilliant cone of whiteness, etching out an enormous circle on the ice next to where the ship stood. Around the inside of the periphery of the pool of light, several hundred spacesuited, eight-foot-tall figures stood four deep in unmoving ranks, their heads bowed and their hands clasped loosely before them. The area within the circle was divided into a series of concentric rings and at regular intervals around each ring rectangular pits had been cut into the ice, each one aligned with the center. By the side of each of the pits lay a metallic, box-shaped container roughly nine feet long and four feet wide.

A small group of figures walked slowly to the center and began moving around the innermost ring, stopping at each pit in turn and watching in silence while the container was lowered before moving on to the next. A second small group followed, filling each of the pits with water from a heated hose; the water froze solid in seconds. When they had finished the first ring they moved out to begin on the second, and continued until they were back at the edge of the circle.

They stood gazing for a long time at the simple memorial that they had erected in the center of the circle--a golden obelisk with an inscription on each face, surmounted by a light that would burn for a hundred years. And as they gazed, their thoughts went back in time to friends and faces that they once had known, and who could never again be more than memories.

Then, when the time had come, they turned away and began filing slowly back toward their ship. When the arc lights were turned out, only the tiny glow of light around the obelisk remained to hold the night at bay.

They had honored the pledge that they had made and carried with them through all the years that had brought them here, from another place, from another time.

Beneath the ice field of Pluto lay the soil of Minerva.

The Giants had come home to lay their dead to rest.

The Shapieron reappeared out of space as suddenly as it had gone. The surveillance radars of Jupiter Five picked up an indistinct echo hurtling in from the void and rapidly consolidating itself as it shed speed at a phenomenal rate. By the time the optical scanners had been brought to bear, there it was, coasting into orbit over Ganymede just like the first time. This time, however, the emotions that greeted its arrival were very different.

The exchange of messages recorded in Jupiter Five's Communications Center Day Log was enthusiastic and friendly.

Shapieron Good afternoon.

J5 Hi. How was the trip?

Shap. Excellent. How has the weather been?

J5 Pretty much the same as ever. How were the engines?

Shap. Never better. Did you save our rooms?

J5 Same ones as before. You wanna go on down?

Shap. Thanks. We know the way.

Within five hours of the Shapieron touching down at Ganymede Main Base, familiar eight-foot-tall figures were clumping up and down the corridors at Pithead once again.

Hunt's conversation with Danchekker had stimulated his curiosity about biological mechanisms for combating the effects of toxins and contaminants in the body, and he spent the next few days accessing the data banks of Jupiter Five to study up on the subject. Shilohin had mentioned that terrestrial life had evolved from early marine species that hadn't developed a secondary circulation system because they hadn't needed one; the warmer environment of Earth had imposed less strenuous demands for oxygen with the result that load-sharing had not been necessary. But it was this same mechanism that had later enabled the emerging Minervan land dwellers to adapt to a C02 -rich atmosphere. The terrestrial animals imported to Minerva had obviously possessed no similar mechanism, and yet they had adapted readily enough to their new home. Hunt was curious to find out how they did it.

His researches failed, however, to throw up anything startling. Each world had evolved its own family of life, and the two systems of fundamental chemistry on which the two families were based were not the same. Minervan chemistry was rather delicate, as Danchekker had deduced long ago from his study of the preserved Minervan fish discovered in the ruins of a wrecked Lunarian base; land animals inheriting such chemistry would be inherently sensitive to certain toxins, including carbon dioxide, and would require an extra line of defense to give them a reasonable tolerance if atmospheric conditions were extreme--hence the adaptation of the secondary system in the earliest land dwellers. Terrestrial chemistry was more rugged and flexible and could survive a far wider range of changes, even without any assistance. And that was really all there was to it.

One afternoon, Hunt found himself sitting in front of the view-screen in one of the computer console rooms at Pithead at the end of another unsuccessful attempt to uncover a new slant on the subject. Having nobody else to talk to, he activated his channel into the Ganymean computer network and discussed the problem with ZORAC. The machine listened solemnly without offering much in the way of comment while Hunt spoke. Afterward it had one comment. "I really don't see much to add, Vic. You seem to have got it pretty wrapped up."

"There's nothing you can think of that I might have left out?" Hunt queried. It seemed a funny question for a scientist to put to a machine, but Hunt had come to know well ZORAC's uncanny ability to spot a missing detail or a small flaw in what appeared to be a watertight line of reasoning.

"No. The evidence adds up to what you've already concluded: Minervan life needed the help of a secondary system to adapt and terrestrial life didn't. That is an observed fact, not a deduction. Therefore there's not a lot I can say."

"No, I guess not," Hunt conceded with a sigh. He flipped a switch to cut off the terminal, lit a cigarette and slumped back in a chair. "It wasn't really that important, I suppose," he commented absently after a while. "I was just curious to see if the differences in biochemistry between our life forms and Minervan ones pointed to anything significant. Looks as if they don't."

"What were you hoping to find?" ZORAC asked. Hunt shrugged automatically.

"Oh, I don't know. . . something that might shed light on the kinds of things we've been asking . . . what happened to all the Minervan land dwellers, what was it that they couldn't survive that the animals from Earth could--we know it wasn't the CO2 concentration now. . . . Things like that."

"Anything unusual, in fact," ZORAC suggested.

"Mmm. . . guess so."

A few seconds passed before ZORAC spoke again. Hunt had the uncanny impression that the machine was turning the proposition over in its mind. Then it said in a matter-of-fact voice:

"Maybe you've been asking the wrong question."

It took a moment for the implication to sink in. Then Hunt snatched the cigarette from his lips and sat forward in his chair with a start.

"What d'you mean?" he asked. "What's wrong with the question?"

"You're asking why Minervan life and terrestrial life were different and succeeding only in proving that the answer is,'because they were.' It's undeniably true, but singularly ineffective in telling you anything new. It's like asking,'Why does salt dissolve in water when sand doesn't?' and coming up with the answer,'because salt's soluble and sand isn't.' Very true, but it doesn't tell you much. That's what you're doing."