Hurtling outward, they passed the orbits of Mars, the asteroids, Jupiter, and Saturn. There, with Earth-made instruments, Brinker located what he sought: Brulow's Comet. So far from the sun, where the fluorescence-inducing radiations were thinned almost to nothing, it glowed hardly at all. And it had almost no tail; it was only a gigantic, tenuous ghost, with a core of stone and magnetic iron fragments. Still dazed, Copeland thought about comets. Wanderers, following elongated orbits that loop tight around the sun at one end and plumb the depths of space at the other. Of all large forms moving through the void, they were the least dense. In coma and tail, they were only intensely rarefied and electrified gas. The great enigma about them was that things so deficient in mass and gravity could hold onto even that much atmosphere for long. Perhaps new gases were baked out of the meteoric core, each time a comet was close to the sun; maybe some of them even renewed their atmosphere periodically, by capturing a little of the tenuous substance of the solar corona, during their very near approaches to it. Brulow's Comet was on the sunward swing, now, gaining speed under solar gravitation; but it still had a long ways to go. Brinker guided the ship down through its coma and toward its lazily-rotating nucleus, where thousands of fragments of iron and rock swirled around their common center of gravity. The chunks clattered against the craft's metal hull, but did no damage at their low speed. Brinker brought the ship to rest at the center of the nucleus, where there was one solid mass of material a hundred yards in diameter. "Well, we're here, Cope," Brinker said grimly. "We don't have to work right away--if you don't want to. We've got too much time." Those two years looming ahead were the worst. If the Moon had been harsh, it was nothing to this eerie place. The heart of this small comet was illumined by faint, shifting phosphorescence, ranging from blue and tarnished silver to delicate if poisonous pink. Perhaps the cause was the same as that of the terrestrial aurora. The silence here was that of space; but the swirling motion of the nucleus suggested a continuous maddening rustle to Copeland. He had to yield to Brinker's wishes. Toil might divert him some, keep him from feeling the tension of time and strangeness so much. "Okay, Brinker," he said. "You win. Brulow's Comet is headed for a close approach to the Earth-Moon system. So you want to be spectacular, and shift it a little from its orbit--so that it will hit the Moon and maybe break its crust. Was that so hard to figure? That sounds pretty big, doesn't it? But I'll humor you. Let's see how far we get ... Since we're here." His sarcasm was tired. * * * * *