Arthur Clarke: A Meeting with Medusa

If he managed to survive until then.

That first day, the Father of the Gods smiled upon him. It was as calm and peaceful here on Jupiter as it had been, years ago, when he was drifting with Webster across the plains of northern India. Falcon had time to master his new skills, until Kon-Tiki seemed an extension of his own body. Such luck was more than he had dared to hope for, and he began to wonder what price he might have to pay for it.

The five hours of daylight were almost over, the clouds below were full of shadows, which gave them a massive solidity they had not possessed when the Sun was higher. Colour was swiftly draining from the sky, except the west itself, where a band of deepening purple lay along the horizon. Above this band was the thin crescent of a closer moon, pale and bleached ainst the utter blackness beyond.

With a speed perceptible to the eye, the Sun went straight down over the edge of Jupiter, over eighteen hundred miles away. The stars came out in their legions and there was the beautiful evening star of Earth, on the very frontier of twilight, reminding him how far he was from home. It followed the Sun down into the west. Man’s first night on Jupiter had gun.

With the onset of darkness, Kon-Tiki started to sink. The balloon was no longer heated by the feeble sunlight and was losing a small part of its buoyancy. Falcon did nothing to increase lift, he had expected this and was planning to descend.

The invisible cloud deck was still over thirty miles below, and he would reach it about midnight. It showed up clearly on the infrared radar, which also reported that it contained a vast array of complex carbon compounds, as well as the usual hydrogen, helium, and ammonia. The chemists were dying for samples of that fluffy, pinkish stuff; though some atmospheric probes had already gathered a few grams, that had only whetted their appetites. Half the basic molecules of life were here, floating high above the surface of Jupiter. And where there was food, could life be far away? That was the question that, after more than a hundred years, no one had been able to answer.

The infrared was blocked by the clouds, but the microwave radar sliced right through and showed layer after layer, all the way down to the hidden surface almost two hundred and fifty miles below. That was barred to him by enormous pressures and temperatures, not even robot probes had ever reached it intact. It lay in tantalising inaccessibility at the bottom of the radar screen, slightly fuzzy, and showing a curious granular structure that his equipment could not resolve.

An hour after sunset, he dropped his first probe. It fell swiftly for about sixty miles, then began to float in the denser atmosphere, sending back torrents of radio signals, which he relayed to Mission Control. Then there was nothing else to do until sunrise, except to keep an eye on the rate of descent, monitor the instruments, and answer occasional queries. While she was drifting in this steady current, Kon-Tiki could look after herself.

Just before midnight, a woman controller came on watch and introduced herself with the usual pleasantries. Ten minutes later she called again, her voice at once serious and excited.

“Howard! Listen in on channel forty-six high gain.”

Channel forty-six? There were so many telemetering circuits that he knew the numbers of only those that were critical, but as soon as he threw the switch, he recognised this one. He was plugged in to the microphone on the probe, floating more than eighty miles below him in an atmosphere now almost as dense as water.

At first, there was only a soft hiss of whatever strange winds stirred down in the darkness of that unimaginable world. And then, out of the background noise, there slowly emerged a booming vibration that grew louder and louder, like the beating of a gigantic drum. It was so low that it was felt as much as heard, and the beats steadily increased their tempo though the pitch never changed. Now it was a swift, almost infrasonic throbbing. Then, suddenly, in mid-vibration, it stopped so abruptly that the mind could not accept the silence, but memory continued to manufacture a ghostly echo in the deepest caverns of the brain.

It was the most extraordinary sound that Falcon had ever heard, even among the multitudinous noises of Earth. He could think of no natural phenomenon that could have caused it, nor was it like the cry of any animal, not even one of the great whales…

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 was 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 aproximate location of the sources. Oddly enough, none of Kon-Tiki’s own external mikes could detect anything except wind noises. The boomings, hatever they were, must have been trapped and channelled beneath an mospheric 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 wer, in Earth’s oceans, quite feeble sounds could travel equally far. And for the obvious assumption that living creatures were responsible, the Exobiobogist quickly ruled that out.

“I’ll be very disappointed,” said Dr Brenner, “if there are no microanisms or plants there. 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 me up with an explanation. What would a blind alien make, Falcon wondered, of the sounds he might hear when standing beside a stormy sea, a geyser, or a volcano, or a waterfall? He might well attribute them to a 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 colour near the horizon, and the cloud layer had become ragged and lumpy, 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.