Iris

some final explosive force vector had given it an impulse toward the center of the ice moon rather than away. The tumbling motion stopped with a few glancing impacts on the frozen, shattered walls as it sank. It came to rest nose down in the deep cavity, its dorsal fin pointing at the black sky, and debris began to accrete all around it. Ultimately the ship, if such it was, would be buried once again. Polarisswung down from its orbit with a single phasingmaneuver and came to rest at its high gate point above the Artifact, hovering on an oxygen jet bled from the Hyloxso tanks. The crew looked down at it through the ship optics, silently examining their find in the harsh yet dim light of the sun. It was simple, almost featureless, a fat, wedge-shaped lifting body, with a tall stabilizer at the stern. There were two winglike control surfaces projecting upward at thirty-degree angles on either side. It appeared to be a soft, pale blue in color, though there were darker spots here and there. On the blunt stern there were five huge black circles, evidently the expansion nozzles of rocket engines mounted in a trapezoidal array. It looked like a primitive human-technology spacecraft blown to unbelievable size. Sealock opened his eyes and glanced over at Krzakwa . 'What do you suppose flew the damn thing, mile-high Watusi ?'

The Selenite's teeth showed briefly, a weak sort of grin. 'I guess we'd better go down and find out.' Turning his attention back to the ship, Brendan said, 'We'll be in for a lot of walking no matter where we land. It probably doesn't matter in this gravity.'

From the lower equipment bay, Ariane called up, 'Why not land right on top of the thing? It's certainly big enough.'

Sealock nodded. 'Why not? We couldn't ask for a flatter surface.' He decreased the flow of gas from the engines and dropped Polaris slowly toward the broad back of the alien vessel. When they were down and the motor stopped, the ship stood canted at a twenty-degree angle. They started to slide, but a slight adjustment to the friction coefficient of the landing pads halted them. Krzakwasat up on his couch, eyes glassy with excitement. 'Suit up. Let's see what we've got.' The four of them stood outside the ship, back in their armored worksuits, on a smooth, tilted azure plain. In the distance they could see the three fins rising toward the black sky and beyond, very far away, the dark, crystalline horizon that hid the walls of the world-sized crater they'd made. The shrouded eye of Iris looked down on them in three-quartersphase, just above one horizon, and the sun, a fat spark, threw its wan light over the other.

'Where do we begin?' mused Methol.

'Maybe at the nearest dark spot,' said Krzakwa . 'They seem to be the only real features anywhere on the dorsal surface. There's one about three hundred meters, um, starboard of here.' They'd landed just to port of the center line, where most of the Artifact's features seemed to be. When they set out for the thing, they ran into immediate difficulty. The surface of the vessel was so smooth and the gravity so low that it was difficult to push off in the long flat leaps of low-g movement, and even harder to come to a stop after landing. Raising the friction on the soles of their boots remedied this, but, since the em-embedding fields induced a corresponding field in the surface that did not immediately dissipate, they had a tendency to stick to the Artifact as they jumped. Any slight asymmetry in takeoff tended to throw them off course. Eventually they made it to the feature. The disk was just a region of somewhat darker blue, in no other way distinguished from the surrounding area. It was neither raised nor depressed, nor did it seem to have a different texture. 'Well,' said Krzakwa , 'this is useless.' He stepped forward onto it, but nothing happened. 'I wonder what it's for?' The others joined him and they began walking around, staring at the circle. An analysis of the thing showed that it was simply a region of slightly enhanced titanium concentration. Sealock suddenly squatted near the center of the disk and said, 'Maybe it's a giant 'O,' with very thick sides. Look.' In front of him, at the circle's focus, was a small white spot, about two centimeters across. It, too, showed no relief.

'Maybe that's just an artifact of whatever process they used to draw this design,' said Methol. 'The compass point,' she laughed suddenly. 'We're wasting our time here. Let's go back to the ship and break out the whole barrage of instruments.' She and Krzakwa turned and started for Polaris, accompanied by Hu, who had been following them silently about, wrapped in whatever web of thoughts her mind was spinning.

Sealock stood for a while longer, staring down at the white spot. He leaned forward and put his thumb over it, then straightened up. The little world about him remained inert. He muttered something, then put his foot over the mark and turned the sole's friction coefficient to maximum. He could feel his boot seem to cement itself to the surface of the Artifact. When he removed it again, the circular dot looked the same. Nothing happened. He thought he felt a slight current being applied to his skin, perhaps imagination and nothing more. Then he shouted.

The others turned at the sound of his voice, which would have been deafening had the corn-circuits not compensated swiftly, and saw the blue disk being swiftly filled by a spreading pool of black. The edge of the hole seemed paper thin, adding to the impression of two-dimensionality. But there was certainly a third dimension here—Sealock hung poised in space for a moment, then, clasping his knees to his chest, he began to fall down into the darkness, drifting slowly in Aello's weak grasp. In a moment he was gone. They rushed wildly back to the edge of the portal and stood looking down into the nothingness below.

'Brendan?'

'I'm still here, Tem.' His voice was crisp in their heads. 'I'm standing on some kind of surface about four meters below you. I can see you outlined against the stars.' He paused and they could sense his excitement through the telemetry circuits. 'There's something very strange going on here.'

'What is it?'

'Well . . . jump down and see. It might be best for you to experience it first hand. Just don't alter your optical settings.'

Krzakwaglanced at Methol and Hu, then shrugged and stepped over the edge. He fell very slowly, taking a long time to drop the four meters. As the darkness engulfed him, he said, 'What am I supposed to be expecting?'

'You'll see.'

'Should I try to land flat-footed?'