The Sentinel - Arthur C. Clarke [104]
It came again, following exactly the same pattern. Now that he was prepared for it, he estimated the length of the sequence; from first faint throb to final crescendo, it lasted just over ten seconds.
And this time there was a real echo, very faint and far away. Perhaps it came from one of the many reflecting layers, deeper in this stratified atmosphere; perhaps it was another, more distant source. Falcon waited for a second echo, but it never came.
Mission Control reacted quickly and asked him to drop another probe at once. With two microphones operating, it would be possible to find the approximate location of the sources. Oddly enough, none of Kon-Tiki’s own external mikes could detect anything except wind noises. The boomings, whatever they were, must have been trapped and channeled beneath an atmospheric reflecting layer far below.
They were coming, it was soon discovered, from a cluster of sources about twelve hundred miles away. The distance gave no indication of their power; in Earth’s oceans, quite feeble sounds could travel equally far. And as for the obvious assumption that living creatures were responsible, the Chief Exobiologist quickly ruled that out.
“I’ll be very disappointed,” said Dr. Brenner, “if there are no microorganisms or plants here. But nothing like animals, because there’s no free oxygen. All biochemical reactions on Jupiter must be low-energy ones—there’s just no way an active creature could generate enough power to function.”
Falcon wondered if this was true; he had heard the argument before, and reserved judgment.
“In any case,” continued Brenner, “some of those sound waves are a hundred yards long! Even an animal as big as a whale couldn’t produce them. They must have a natural origin.”
Yes, that seemed plausible, and probably the physicists would be able to come up with an explanation. What would a blind alien make, Falcon wondered, of the sounds he might hear when standing beside a stormy sea, or a geyser, or a volcano, or a waterfall? He might well attribute them to some huge beast.
About an hour before sunrise the voices of the deep died away, and Falcon began to busy himself with preparation for the dawn of his second day. Kon-Tiki was now only three miles above the nearest cloud layer; the external pressure had risen to ten atmospheres, and the temperature was a tropical thirty degrees. A man could be comfortable here with no more equipment than a breathing mask and the right grade of heliox mixture.
“We’ve some good news for you,” Mission Control reported, soon after dawn. “The cloud layer’s breaking up. You’ll have partial clearing in an hour—but watch out for turbulence.”
“I’ve already noticed some,” Falcon answered. “How far down will I be able to see?”
“At least twelve miles, down to the second thermocline. That cloud deck is solid—it never breaks.”
And it’s out of my reach, Falcon told himself; the temperature down there must be over a hundred degrees. This was the first time that any balloonist had ever had to worry, not about his ceiling, but about his basement!
Ten minutes later he could see what Mission Control had already observed from its superior vantage point. There was a change in color near the horizon, and the cloud layer had become ragged and humpy, as if something had torn it open. He turned up his little nuclear furnace and gave Kon-Tiki another three miles of altitude, so that he could get a better view.
The sky below was clearing rapidly, completely, as if something was dissolving the solid overcast. An abyss was opening before his eyes. A moment later he sailed out over the edge of a cloud canyon about twelve miles deep and six hundred miles wide.
A new world lay spread beneath him; Jupiter had stripped away one of its many veils. The second layer of clouds, unattainably far below, was much darker in color than the first. It was almost salmon pink, and curiously mottled with little islands