Though he did not for a moment doubt Floyd's report – his new Second Officer was very competent, and the Captain was pleased that he had never brought up the subject of his famous grandfather -there could be an innocent explanation. The sniffer might have been misled by other chemicals with nervous molecular bondings.

They could go down into the hold and force open the package. No – that might be dangerous, and could cause legal problems as well. Best to go straight to the top; he'd have to do that anyway, sooner or later.

'Please bring Dr Anderson here – and don't mention this to anyone else,'

'Very good, Sir.' Chris Floyd gave a respectful but quite unnecessary salute, and left the room in a smooth, effortless glide.

The leader of the science team was not accustomed to zero gravity, and his entrance was quite clumsy. His obvious genuine indignation did not help, and he had to grab the Captain's desk several times in an undignified manner.

'Explosives! Of course not! Let me see the manifest... 2/456...'

Dr Anderson pecked out the reference on his portable keyboard, and slowly read off: "Mark V penetrometers, Quantity three." Of course – no problem.'

'And just what,' said the Captain, 'is a penetrometer?' Despite his concern, he had difficulty in suppressing a smile; it sounded a little obscene.

'Standard planetary sampling device. You drop it, and with any luck it will give you a core up to ten metres long – even in hard rock. Then it sends back a complete chemical analysis. The only safe way to study places like dayside Mercury – or Io, where we'll drop the first one.'

'Dr Anderson,' said the Captain, with great selfrestraint, 'you may be an excellent geologist, but you don't know much about celestial mechanics. You can't just drop things from orbit -'

The charge of ignorance was clearly unfounded, as the scientist's reaction proved.

'The idiots!' he said. 'Of course, you should have been notified.'

'Exactly. Solid fuel rockets are classified as "Hazardous Cargo". I want clearance from the underwriters, and your personal assurance that the safety systems are adequate; otherwise, they go overboard. Now, any other little surprises? Were you planning seismic surveys? I believe those usually involve explosives...'

A few hours later, the somewhat chastened scientist admitted that he had also found two bottles of elemental fluorine, used to power the lasers which could zap passing celestial bodies at thousand-kilometre ranges for spectrographic sampling. As pure fluorine was about the most vicious substance known to man, it was high on the list of prohibited materials – but, like the rockets which drove the penetrometers down to their targets, it was essential for the mission.

When he was quite satisfied that all the necessary precautions had been taken, Captain Laplace accepted the scientist's apologies, and his assurance that the oversight was entirely due to the haste with which the expedition had been organized.

He felt sure that Dr Anderson was telling the truth, but already he felt that there was something odd about the mission.

Just how odd he could never have imagined.

Before the detonation of Jupiter, Io had been second only to Venus as the best approximation to Hell in the Solar System. Now that Lucifer had raised its surface temperature another couple of hundred degrees, even Venus could no longer compete.

The sulphur volcanoes and geysers had multiplied their activity, now reshaping the features of the tormented satellite in years rather than decades. The planetologists had given up any attempt at mapmaking, and contented themselves with taking orbital photographs every few days. From these, they had constructed awe-inspiring time-lapse movies of inferno in action.

Lloyd's of London had charged a stiff premium for this leg of the mission, but Io posed no real danger to a ship doing a flyby at a minimum range of ten thousand kilometres – and over the relatively quiescent nightside at that.

As he watched the approaching yellow and orange globe – the most improbably garish object in the entire Solar System – Second Officer Chris Floyd could not help recalling the time, now half a century ago, when his grandfather had come this way. Here, Leonov had made its rendezvous with the abandoned Discovery, and here Dr Chandra had reawakened the dormant computer Hal. Then both ships had flown on to survey the enormous black monolith hovering at L1, the Inner Lagrange Point between Io and Jupiter.

Now the monolith was gone – and so was Jupiter. The minisun that had risen like a phoenix from the implosion of the giant planet had turned its satellites into what was virtually another Solar System, though only on Ganymede and Europa were there regions with Earthlike temperatures. How long that would continue to be the case, no-one knew. Estimates of Lucifer's life-span ranged from a thousand to a million years.

Galaxy's science team looked wistfully at the L1 point, but it was now far too dangerous to approach. There had always been a river of electrical energy – the Io 'flux tube' – flowing between Jupiter and its inner satellite, and the creation of Lucifer had increased its strength several hundredfold. Sometimes the river of power could even be seen by the naked eye, glowing yellow with the characteristic light of ionized sodium. Some engineers on Ganymede had talked hopefully about tapping the gigawatts going to waste next door, but no-one could think of a plausible way of doing so.

The first penetrometer was launched, with vulgar comments from the crew, and two hours later drove like a hypodermic needle into the festering satellite. It continued to operate for almost five seconds – ten times its designed lifetime – broadcasting thousands of chemical, physical and rheological measurements, before Io demolished it.

The scientists were ecstatic; van der Berg was merely pleased. He had expected the probe to work; Io was an absurdly easy target. But if he was right about Europa, the second penetrometer would surely fail.

Yet that would prove nothing; it might fail for a dozen good reasons. And when it did, there would be no alternative but a landing.

Which, of course, was totally prohibited – not only by the laws of man.

ASTROPOL – which, despite its grandiose title, had disappointingly little business off Earth – would not admit that SHAKA really existed. The USSA took exactly the same position, and its diplomats became embarrassed or indignant when anyone was tactless enough to mention the name.

But Newton's Third Law applies in politics, as in everything else. The Bund had its extremists -though it tried, sometimes not very hard, to disown them – continually plotting against the USSA. Usually they confined themselves to attempts at commercial sabotage, but there were occasional explosions, disappearances and even assassinations.

Needless to say, the South Africans did not take this lightly. They reacted by establishing their own official counter-intelligence services, which also had a rather free-wheeling range of operations – and likewise claimed to know nothing about SHAKA. Perhaps they were employing the useful CIA invention of 'plausible deniability'. It is even possible that they were telling the truth.

According to one theory, SHAKA started as a codeword, and then – rather like Prokofiev's 'Lieutenant Kije' – had acquired a life of its own, because it was useful to various clandestine bureaucracies. This would certainly account for the fact that none of its members had ever defected, or even been arrested.

But there was another, somewhat far-fetched explanation for this, according to those who believed that SHAKA really did exist. All its agents had been psychologically conditioned to self-destruct before there was any possibility of interrogation.