There was no sign that the impact had done the slightest damage to Rama’s spinning walls; but this mark had produced the slight fluctuation in brightness that had led to Stenton’s discovery.

The images from the other cameras added nothing new. However, the trajectories their pods traced through Rama’s minute gravitational field gave one other vital piece of information—the mass of the cylinder.

It was far too light to be a solid body. To nobody’s great surprise, it was clear that Rama must be hollow.

The long-hoped-for, long-feared encounter had come at last. Mankind was about to receive its first visitor from the stars.

Commander Norton remembered those first TV transmissions, which he had replayed so many times, during the final minutes of the rendezvous. But there was one thing no electronic image could possibly convey—and that was Rama’s overwhelming size.

He had never received such an impression when landing on a natural body like the Moon or Mars. Those were worlds, and one expected them to be big. Yet he had also landed on Jupiter VIII, which was slightly larger than Rama—and that had seemed quite a small object.

It was very easy to resolve the paradox. His judgement was wholly altered by the fact that this was an artifact, millions of times heavier than anything that Man had ever put into space. The mass of Rama was at least ten million million tons; to any spaceman, that was not only an awe-inspiring, but a terrifying thought. No wonder that he sometimes felt a sense of insignificance, and even depression, as that cylinder of sculptured, ageless metal filled more and more of the sky.

There was also a sense of danger here that was wholly novel to his experience. In every earlier landing he had known what to expect; there was always the possibility of accident, but never of surprise. With Rama, surprise was the only certainty.

Now Endeavour was hovering less than a thousand metres above the North Pole of the cylinder, at the very centre of the slowly turning disc. This end has been chosen because it was the one in sunlight; as Rama rotated, the shadows of the short enigmatic structures near the axis swept steadily across the metal plain. The northern face of Rama was a gigantic sundial, measuring out the swift passage of its four-minute day.

Landing a five-thousand-ton spaceship at the centre of a spinning disc was the least of Commander Norton’s worries. It was no different from docking at the axis of a large space station; Endeavour’s lateral jets had already given her a matching spin, and he could trust Lieutenant Joe Calvert to put her down as gently as a snowflake, with or without the aid of the nay computer.

“In three minutes,” said Joe, without taking his eyes from the display, “we’ll know if it’s made of antimatter.”

Norton grinned, as he recalled some of the more hair-raising theories about Rama’s origin. If that unlikely speculation was true, in a few seconds there would be the biggest bang since the solar system was formed. The total annihilation of ten thousand tons would, briefly, provide the planets with a second sun.

Yet the mission profile had allowed even for this remote contingency; Endeavour had squirted Rama with one of her jets from a safe thousand kilometres away. Nothing whatsoever had happened when the expanding cloud of vapour arrived on target—and a matter-antimatter reaction involving even a few milligrams would have produced an awesome firework display.

Norton, like all space commanders, was a cautious man. He had looked long and hard at the northern face of Rama, choosing the point of touchdown. After much thought, he had decided to avoid the obvious spot—the exact centre, on the axis itself. A clearly marked circular disc, a hundred metres in diameter, was centred on the Pole, and Norton had a strong suspicion that this must be the outer seal of an enormous airlock. The creatures who had built this hollow world must have had some way of taking their ships inside. This was the logical place for the main entrance, and Norton thought it might be unwise to block the front door with his own vessel.

But this decision generated other problems. If Endeavour touched down even a few metres from the axis, Rama’s rapid spin would start her sliding away from the pole. At first, the centrifugal force would be very weak, but it would be continuous and inexorable. Commander Norton did not relish the thought of his ship slithering across the polar plain, gaining speed minute by minute until it was slung off into space at a thousand kilometres an hour when it reached the edge of the disc.

It was possible that Rama’s minute gravitational field—about one thousandth of Earth’s—might prevent this from happening. It would hold Endeavour against the plain with a force of several tons, and if the surface was sufficiently rough the ship might stay near the Pole. But Commander Norton had no intention of balancing an unknown frictional force against a quite certain centrifugal one.

Fortunately, Rama’s designers had provided an answer. Equally spaced around the polar axis were three low, pillbox-shaped structures, about ten metres in diameter. If Endeavour touched down between any two of these, the centrifugal drift would fetch her up against them and she would be held firmly in place, like a ship glued against a quayside by the incoming waves.

“Contact in fifteen seconds,” said Joe. As he tensed himself above the duplicate controls, which he hoped he would not have to touch, Commander Norton became acutely aware of all that had come to focus on this instant of time. This, surely, was the most momentous landing since the first touchdown on the Moon, a century and a half ago.

The grey pill-boxes drifted slowly upwards outside the control port. There was the last hiss of a reaction jet, and a barely perceptible jar.

In the weeks that had passed, Commander Norton had often wondered what he would say at this moment. But now that it was upon him, History chose his words, and he spoke almost automatically, barely aware of the echo from the past:

“Rama Base. Endeavour has landed.” As recently as a month ago, he would never have believed it possible. The ship had been on a routine mission, checking and emplacing asteroid warning beacons, when the order had come. Endeavour was the only spacecraft in the solar system which could possibly make a rendezvous with the intruder before it whipped round the sun and hurled itself back towards the stars. Even so, it had been necessary to rob three other ships of the Solar Survey, which were now drifting helplessly until tankers could refuel them. Norton feared that it would be a long time before the skippers of Calypso, Beagle and Challenger would speak to him again.

Even with all this extra propellant, it had been a long hard chase; Rama was already inside the orbit of Venus when Endeavour caught up with her. No other ship could ever do so; this privilege was unique, and not a moment of the weeks ahead was to be wasted. A thousand scientists on Earth would have cheerfully mortgaged their souls for this opportunity; now they could only watch over the TV circuits, biting their lips and thinking how much better they could do the job. They were probably right, but there was no alternative. The inexorable laws of celestial mechanics had decreed that Endeavour was the first, and the last, of all Man’s ships that would ever make contact with Rama.

The advice he was continually receiving from Earth did little to alleviate Norton’s responsibility. If split-second decisions had to be made, no one could help him; the radio time-lag to Mission Control was already ten minutes, and increasing. He often envied the great navigators of the past, before the days of electronic communications, who could interpret their sealed orders without continual monitoring from headquarters. Why they made mistakes, no one ever knew.