When the airlock's outer hatch opened, the MSV was floating fifteen metres away. Marcus datavised an order into his manoeuvring pack processor, and the gas jets behind his shoulder fired, pushing him towards the small egg-shaped vehicle. Wai extended two of the MSV's three waldo arms in greeting. Each of them ended in a simple metal grid, with a pair of boot clamps on both sides.

Once all four of her passengers were locked into place, Wai piloted the MSV in towards the disc. The rock particle had a slow, erratic tumble, taking a hundred and twenty hours to complete its cycle. As she approached, the flattish surface with the dish was just turning into the sunlight. It was a strange kind of dawn, the rock's crumpled grey-brown crust speckled by the sharp black shadows of its own rolling prominences, while the dish was a lake of infinite black, broken only by the jagged spire of the horn rising from its centre. The xenoc ship was already exposed to the amber light, casting its bloated sundial shadow across the featureless glassy cliff. She could see the ripple of different ores and mineral strata frozen below the glazed surface, deluding her for a moment that she was flying towards a mountain of cut and polished onyx.

Then again, if Victoria's theory was right, she could well be.

«Take us in towards the top of the wedge,» Marcus datavised. «There's a series of darker rectangles there.»

«Will do,» she responded. The MSV's chemical thrusters pulsed in compliance.

«Do you see the colour difference near the frayed edges of the shell?» Schutz asked. «The stuff's turning grey. It's as if the decay is creeping inwards.»

«They must be using something like our molecular-binding-force generators to resist vacuum ablation,» Marcus datavised. «That's why the main section is still intact.»

«It could have been here for a long time, then.»

«Yeah. We'll know better once Wai collects some samples from the tower.»

There were five rectangles arranged in parallel, one and a half metres long and one metre wide. The shell material below the shorter edge of each one had a set of ten grooves leading away down the curve.

«They look like ladders to me,» Antonio datavised. «Would that mean these are airlocks?»

«It can't be that easy,» Schutz replied.

«Why not?» Marcus datavised. «A ship this size is bound to have more than one airlock.»

«Yeah, but five together?»

«Multiple redundancy.»

«With technology this good?»

«That's human hubris. The ship still blew up, didn't it?»

Wai locked the MSV's attitude fifty metres above the shell section. «The micro-pulse radar is bouncing right back at me,» she informed them. «I can't tell what's below the shell, it's a perfect electromagnetic reflector. We're going to have communication difficulties once you're inside.»

Marcus disengaged his boots from the grid and fired his pack's gas jets. The shell was as slippery as ice, neither stikpads nor magnetic soles would hold them to it.

«Definitely enhanced valency bonds,» Schutz datavised. He was floating parallel to the surface, holding a sensor block against it. «It's a much stronger field than Lady Mac 's. The shell composition is a real mix; the resonance scan is picking up titanium, silicon, boron, nickel, silver, and a whole load of polymers.»