18 - Through the Asteroids
Week after week, running like a streetcar along the tracks of her utterly predetermined orbit, Discovery swept past the orbit of Mars and on toward Jupiter. Unlike all the vessels traversing the skies or seas of Earth, she required not even the most minute touch on the controls. Her course was fixed by the laws of gravitation; there were no uncharted shoals, no dangerous reefs on which she would run aground. Nor was there the slightest danger of collision with another ship; for there was no vessel - at least of Man's making - anywhere between her and the infinitely distant stars.
Yet the space which she was now entering was far from empty. Ahead lay a no-man's land threaded by the paths of more than a million asteroids - less than ten thousand of which had ever had their orbits precisely determined by astronomers. Only four were over a hundred miles in diameter; the vast majority were merely giant boulders, trundling aimlessly through space.
There was nothing that could be done about them; though even the smallest could completely destroy the ship if it slammed into it at tens of thousands of miles an hour, the chance of this happening was negligible.
On the average, there was only one asteroid in a volume a million miles on a side; that Discovery should also happen to occupy this same point, and at the same time, was the very least of her crew's worries.
On Day 86 they were due to make their closest approach to any known asteroid, It had no name - merely the number 7794 - and was a fifty-yard-diameter rock that had been detected by the Lunar Observatory in 1997 and immediately forgotten except by the patient computers of the Minor Planet Bureau.
When Bowman came on duty, Hal promptly reminded hint of the forthcoming encounter - not that he was likely to have forgotten the only scheduled in-flight event of the entire voyage, The track of the asteroid against the stars, and its coordinates at the moment of closest approach, had already been printed out on the display screens. Listed also were the observations to be made or attempted; they were going to be very busy when 7794 flashed past them only nine hundred miles away, at a relative speed of eighty thousand miles an hour.
When Bowman asked Hal for the telescopic display, a sparsely sprinkled star field flashed onto the screen. There was nothing that looked like an asteroid; all the images, even under the highest magnification, were dimensionless points of light.
"Give me the target reticule," asked Bowman. Immediately four faint, narrow lines appeared, bracketing a tiny and undistinguished star. He stared at it for many minutes, wondering if Hal could possibly be mistaken; then he saw that the pinpoint of light was moving, with barely perceptible slowness, against the background of the stars. It might still be half a million miles away - but its movement proved that, as cosmic distances went, it was almost near enough to touch.
When Poole joined him on the control deck six hours later, 7794 was hundreds of times more brilliant, and was moving so swiftly against its background that there was no question of its identity. And it was no longer a point of light; it had begun to show a clearly visible disk.
They stared at that passing pebble in the sky with the emotions of sailors on a long sea voyage, skirting a coast on which they cannot land. Though they were perfectly well aware that 7794 was only a lifeless, airless chunk of rock, this knowledge scarcely affected their feelings. It was the only solid matter they would meet this side of Jupiter - still two hundred million miles away.
Through the high-powered telescope, they could see that the asteroid was very irregular, and turning slowly end over end. Sometimes it looked like a flattened sphere, sometimes it resembled a roughly shaped block; its rotation period was just over two minutes. There were mottled patches of light and shade distributed apparently at random over its surfa…
