They scanned the flight of steps with their helmet-lights, could see no conceivable hazard, and Dr. Ernst got Commander Norton’s permission to descend. A minute later, she was cautiously testing the surface of the Sea.

Her foot slithered almost frictionlessly back and forth. The material felt exactly like ice. It was ice.

When she struck it with her hammer, a familiar pattern of cracks radiated from the impact point, and she had no difficulty in collecting as many pieces as she wished. Some had already melted when she held up the sample holder to the light; the liquid appeared to be slightly turbid water, and she took a cautious sniff.

“Is that safe?” Rodrigo called down, with a trace of anxiety.

“Believe me, Boris,” she answered, “if there are any pathogens around here that have slipped through my detectors, our insurance policies lapsed a week ago.”

But Boris had a point. Despite all the tests that had been carried out, there was a very slight risk that this substance might be poisonous, or might carry some unknown disease. In normal circumstances, Dr. Ernst would not have taken even this minuscule chance. Now, however, time was short and the stakes were enormous. If it became necessary to quarantine Endeavour, that would be a very small price to pay for her cargo of knowledge.

“It’s water, but I wouldn’t care to drink it—it smells like an algae culture that’s gone bad. I can hardly wait to get it to the lab.”

“Is the ice safe to walk on?”

“Yes, solid as a rock.”

“Then we can get to New York.”

“Can we, Pieter? Have you ever tried to walk across four kilometres of ice?”

“Oh—I see what you mean. Just imagine what Stores would say, if we asked for a set of skates! Not that many of us would know how to use them, even if we had any aboard.”

“And there’s another problem,” put in Boris Rodrigo. “Do you realize that the temperature is already above freezing? Before long, that ice is going to melt. How many spacemen can swim four kilometres? Certainly not this one…”

Dr. Ernst rejoined them at the edge of the cliff, and held up the small sample bottle in triumph.

“It’s a long walk for a few cc’s of dirty water, but it may teach us more about Rama than anything we’ve found so far. Let’s head for home.”

They turned towards the distant lights of the Hub, moving with the gentle, loping strides which had proved the most comfortable means of walking under this reduced gravity. Often they looked back, drawn by the hidden enigma of the island out there in the centre of the frozen sea. And just once, Dr. Ernst thought she felt the faint suspicion of a breeze against her cheek. It did not come again, and she quickly forgot all about it.

“As you know perfectly well, Dr. Perera,” said Ambassador Bose in a tone of patient resignation, “few of us share your knowledge of mathematical meteorology. So please take pity on our ignorance.”

“With pleasure,” answered the exobiologist, quite unabashed. “I can explain it best by telling you what is going to happen inside Rama—very soon.”

“The temperature is now about to rise, as the solar heat pulse reaches the interior. According to the latest information I’ve received, it’s already above freezing point. The Cylindrical Sea will soon start to thaw; and unlike bodies of water on Earth, it will melt from the bottom upwards. That may produce some odd effects but I’m much more concerned with the atmosphere.”

“As it’s heated, the air inside Rama will expand—and will attempt to rise towards the central axis. And this is the problem. At ground level, although it’s apparently stationary, it’s actually sharing the spin of Rama—over eight hundred kilometres an hour. As it rises towards the axis it will try to retain that speed—and it won’t be able to do so, of course. The result will be violent winds and turbulence; I estimate velocities of between two and three hundred kilometres an hour.”

“Incidentally, very much the same thing occurs on Earth. The heated air at the Equator—which shares the Earth’s sixteen-hundred-kilometres-an-hour spin—runs into the same problem when it rises and flows north and south.”

“Ah, the Trade Winds! I remember that from my geography lessons.”

“Exactly, Sir Robert. Rama will have Trade Winds, with a vengeance. I believe they’ll last only a few hours, and then some kind of equilibrium will be restored. Meanwhile, I should advise Commander Norton to evacuate—as soon as possible. Here is the message I propose sending.”

With a little imagination, Commander Norton told himself, he could pretend that this was an improvised night camp at the foot of some mountain in a remote region of Asia or America. The clutter of sleeping pads, collapsible chain and tables, portable power plant, lighting equipment, electrosan toilets, and miscellaneous scientific apparatus would not have looked out of place on Earth—especially as there were men and women working here without life-support systems.

Establishing Camp Alpha had been very hard work, for everything had had to be man-handled through the chain of airlocks, sledded down the slope from the Hub, and then retrieved and unpacked. Sometimes, when the braking parachutes had failed, a consignment had ended up a good kilometre away out on the plain. Despite this, several crewmembers had asked permission to make the ride; Norton had firmly forbidden it. In an emergency, however, he might be prepared to reconsider the ban.

Almost all this equipment would stay here, for the labour of carrying it back was unthinkable—in fact, impossible. There were times when Commander Norton felt an irrational shame at leaving so much human litter in this strangely immaculate place. When they finally departed, he was prepared to sacrifice some of their precious time to leave everything in good order. Improbable though it was, perhaps millions of years hence, when Rama shot through some other star system, it might have visitors again. He would like to give them a good impression of Earth.

Meanwhile, he had a rather more immediate problem. During the last twenty-four hours he had received almost identical messages from both Mars and Earth. It seemed an odd coincidence; perhaps they had been commiserating with each other, as wives who lived safely on different planets were liable to do under sufficient provocation. Rather pointedly, they had reminded him that even though he was now a great hero, he still had family responsibilities.

The Commander picked up a collapsible chair, and walked out of the pool of light into the darkness surrounding the camp. It was the only way he could get any privacy, and he could also think better away from the turmoil. Deliberately turning his back on the organized confusion behind him, he began to speak into the recorder slung around his neck.

“Original for personal file, dupes to Mars and Earth. Hello, darling—yes, I know I’ve been a lousy correspondent, but I haven’t been aboard ship for a week. Apart from a skeleton crew, we’re all camping inside Rama, at the foot of the stairway we’ve christened Alpha.”

“I have three parties out now, scouting the plain, but we’ve made disappointingly slow progress, because everything has to be done on foot. If only we had some means of transport! I’d be very happy to settle for a few electric bicycles… they’d be perfect for the job.”

“You’ve met my medical officer, Surgeon-Commander Ernst—” He paused uncertainly; Laura had met one of his wives, but which? Better cut that out.

Erasing the sentence, he began again.

“My MO, Surgeon-Commander Ernst, led the first group to reach the Cylindrical Sea, fifteen kilometres from here. She found that it was frozen water, as we’d expected—but you wouldn’t want to drink it. Dr. Ernst says it’s a dilute organic soup, containing traces of almost any carbon compound you care to name, as well as phosphates and nitrates and dozens of metallic salts. There’s not the slightest sign of life—not even any dead micro-organisms. So we still know nothing about the biochemistry of the Ramans… though it was probably not wildly different from ours.”