And the tremendous mass of the hulk was once more hurled forward into the heart of the solar system.

CHAPTER 37

At Mercury the Shrapnel entered a low equatorial orbit, and a small, low-powered shuttle flew up to bring Stef, King, Trant and a couple of ISF guards down to the surface. The little ship was piloted by ISF officers, who saluted Stef when she boarded while simultaneously security-scanning her. The shuttle had only one cabin, fronted by the pilot with the passengers in the back, and while the passengers strapped in Stef heard the crew talk through more complicated security protocols. Evidently this wasn’t a place where casual landings were welcome.

They came down in a sweeping powered descent across a shattered landscape. The shadows of crater-rim mountains, wave after frozen rocky wave of them, stretched across broken lava plains.

Trant turned to Stef. ‘Do you know where you are? On Mercury, I mean.’

Stef shrugged. ‘I only came back once to Mercury since the Angelia launch. It was a memorial service for my father after he died, given by the staff he worked with here.’

‘I know. I was there, though we didn’t speak.’

‘I think this must be the Caloris basin.’ A tremendous impact crater that dominated one face of the planet. ‘Given the scale of the cratering features.’

‘Correct. The result of an impact that couldn’t have been much bigger, to have left any planet behind at all. I suppose you don’t need to know much about Mercury to guess that much.’

‘I’ve had no briefing,’ Stef reminded her testily. ‘So it’s to be guessing games, is it, all the way down?’

‘We want you here to take a fresh look at what we found. I suggested it was best not to prejudice you in any way. Blame me, if you like.’

Stef felt a shiver of awe, flying over this tremendous ruined landscape, which itself concealed a much more exotic mystery. What the hell were they being so secretive about?

On the ground, in the chaotic shadows of Caloris, they were bundled into a rover. There was a driver and a couple of crew, all in ISF uniforms. The two security goons who had come down from orbit with them followed too. Making her way to a seat in the rover, Stef experienced a gravity that was twice the moon’s, a third of Earth’s, a gravity that felt oddly familiar, a body memory from her childhood.

The rover rolled off, and through the small windows Stef glimpsed the landscape of Mercury, for her a peculiar mix of alien and familiar. The sun was just below the horizon here, though a smear of coronal light spread up into the sky. The shuttle landing site behind her was lit by brilliant floods.

‘Here.’ Trant opened a hatch and pulled out pressure suits. ‘One each. We’ll suit up en route in the rover.’

King awkwardly hauled his own suit over his bulk. ‘We’re making straight for the site.’

Stef asked, ‘What site?’

Trant said, ‘This is, or was, just another exploratory drilling site.’

‘You were looking for kernels.’

‘Essentially, though Mercury is also still exporting metals to the rest of the inner system. Stef, you’ll find dormitories in the well-head domes, showers, galleys. If you need a break before we descend . . .’

Descend into what? Every bit of information they gave her seemed to lead only to more questions. Let them play their games. ‘Let’s just get on with it.’ Trying not to let their evident urgency transmit itself to her, she pulled on her suit, ISF standard issue, a piece of kit she was used to. The smart fabric slid into form-fitting shape around her; as the suit recognised her a panel on the chest lit up with her mugshot, rank, commission number, name: KALINKSI, STEPHANIE P.

King smiled. ‘That’s correct, isn’t it? P for Penelope.’

Stef pulled a face. ‘A name I always hated even more than “Stephanie”. So you found kernels in Caloris, right?’

Trant looked out at the smashed landscape. ‘We’ve developed pretty efficient ways to prospect for kernels, even from orbit. We look for concentrations of the kernels’ distinctive energy signature, at sites easy to mine. The heart of Caloris has given us some rich pickings, actually. The kernel lodes here aren’t always quite as deep as elsewhere on the planet, and the ancient impact shattered the bedrock, making it relatively easy to get through. “Relatively” being the word.’

Stef thought that over. ‘Which implies that the Caloris impact came later than whatever event laid down the kernels.’

King nodded approvingly. ‘That’s what my tame geologists deduce. Even though the Caloris event itself was very old, a relic of the planet-formation days. The kernels have been down there a long time; whatever created them, or implanted them, was a very early event in terms of the history of Mercury – hell, of the solar system itself. So we drilled down into the floor of the crater, and that itself was a challenge, I can tell you. But what we found – well, you’ll see for yourself.’

The rover had to pass through a couple more security cordons before pulling up at what was evidently a drilling site, dominated by a single massive rig standing on an area of relative flatness. Stef saw hab domes covered in regolith for solar-radiation screening, a few more rigs much smaller in scale, and massive specialised vehicles.

As they unbuckled, Trant pointed out the equipment. ‘The rigs are structures of high-strength, high-temperature-tolerant carbon. Those smaller rigs were the first to make the discovery we’re going to show you. We brought out the heavy-duty gear to allow human access to the find; that big momma over there drilled out the shaft you’re going to be riding down today . . .’

A flexible transfer tunnel snaked out from a dome towards the rover. Trant led them through a brisk check of their pressure suits. ‘We’ll be riding a pressurised car down the shaft,’ she said. ‘But we’ll wear the suits as a precaution anyhow. And of course the base chamber isn’t pressurised at all.’

Stef tried to figure out these pieces of the puzzle as she went through the routine of interrogating her suit’s functions. Shaft? Base chamber?

The rover hatch opened up, and they passed through the flexible tunnel to the dome. The interior was functional, with lab areas, bathrooms, suit lockers, a galley, bunks. A handful of staff here, in shirts and shorts, working or eating handheld snacks, eyed the newcomers in their pressure suits curiously, but didn’t approach them. Stef felt she could have been inside any pioneering-science-type establishment almost anywhere in the solar system, off Earth.

But this particular facility was dominated by a transparently walled elevator car, set at the very centre of the dome where the roof was highest, attached by winched cables to a stout metal frame. And the car was suspended over an open shaft, from which fluorescent light leaked.

A shaft. A hole in the Mercury ground. Into which, evidently, Stef was going to have to descend. She felt a frisson of fear, and she was grateful for her ISF training, for the ability it gave her to function despite her fear, even if she couldn’t hide it, probably.

Stef was led straight to the elevator, with Trant, King, and the two ISF goons who had ridden down from orbit with them and had barely spoken a word, even to each other. They all crowded into the car. It contained a crate, Stef presumed containing supplies or emergency gear. A door, transparent as the walls, slid closed behind them.

Immediately the car began to descend, with a soft, low-gravity lurch. The dome and its inhabitants ascended out of Stef’s sight, and the walls of the shaft rose up to enclose the car.

The shaft walls were smooth, featureless, and it was impossible to judge directly the car’s speed of descent. But Stef could feel the acceleration.