And he recalled with a chill of gooseflesh that Neptune was pulling the satellite nearly seven tenths of a meter closer every year, and in about 660 million years Triton would come crashing down in pieces upon the planet. He tried to divert his thoughts from this inevitable catastrophe to the hope that by the time his distant descendants had to worry about it, they would have found a way out of Neptune. He tried not to think about how he could produce enough descendants. The group was too small, too ill-equipped to give birth to a population that would have a chance of increasing.

Vinny was about to suggest heading for the western rim and looking for a place to drop anchor when Lenny pointed out a patch of clear, uncrusted lava and announced, “Deeper! Deeper! We’ve got to go deeper.”

“But that’s crazy,” said Vinny. “They’ll never find us here.”

“Oh, they’ll find us, all right. But where we’re going they’ll have to be crazy to follow us.”

“No.” Vinny looked around. “Surely you don’t agree with this,” he implored Sharon and Robyn. But the women uttered no objections, and a horrid sense of fatality passed through Vinny as Lenny circled the clearing, expelled a puff of slush, and allowed Gaius to settle belly first on the water-ethane boundary.

For long seconds they floated like a ship in the water-lava lake, while Lenny collected data on relative temperatures, masses, and densities.

Again Vinny looked at Sharon and Robyn. “I don’t much relish the idea of looking up through the wrong end of a volcano while our enemies wave good-bye from the right end.”

“Vinny, there is no place to go but down,” Lenny insisted. “Now bring yourself to order and save yourself!” And then, with a cycling of pumps, the crew compartment slid beneath the surface, trailing long ropes held up by balloons. One of the balloons valved huge billows of warm slush into the sky, and the ropes suddenly picked up momentum in their plunge.

The valving balloon went down with an audible gulp.

Vinny did as he was told: stiffened his spine and diverted his thoughts from the mounting pressure outside. He paid closer attention to chemical analyses from the spiders—and he could not help paying close attention. Life had just turned up in what seemed to him the most unlikely place in the universe. It was very primitive, microscopic life, but life nonetheless. This sea, unlike the one above, was not so much a primordial soup as a very dilute broth; yet the spiders were registering individual cells, occasionally stitched together to form balls or microfilaments.

By their mere existence they generated enough questions to keep the four Lunarians busy for decades. For a start—just for a start—there was the question of what food sources kept the cells alive. Vinny tried to imagine what would happen if the chemistry of this world had been slightly different, so that life could evolve not only under water but up there, on the icy seafloor beyond the crater rim. What would it be like, he wondered, to behold a fishlike creature—if the like could ever evolve here— erupting onto the ice fields through Mirror Lake? The “fish” would die violently, its blood freezing solid within seconds. If, before it died, it were to embrace an inhabitant of the Neptunian surface, the embrace would feel like the touch of molten lead to the surface dweller. The “fish” would seem an impossible creation—deadly to the touch, living in lava, and turning to stone the instant it was exposed to the ethane-methane “atmosphere.”