Joseph B. Shannon, Mission Director of Jupiter Five, orbiting two thousand miles above the surface of Ganymede, stood in an instrumentation bay near one end of the mile-and-a-quarter-long ship’s command center. He was watching a large mural display screen from behind a knot of spellbound ship’s officers and UNSA scientists. The screen showed an undulating landscape of oranges, yellows, and browns as it lay cringing beneath a black sky made hazy by a steady incandescent drizzle falling from somewhere above, while in the far distance half the skyline was erupting in a boiling column of colors that exploded upward off the top of the picture.
It had been fifty-two years before—the year that Shannon was born—when other scientists at the Jet Propulsion Laboratory in Pasadena had marveled at the first close-ups of Io to be sent back by the Voyager I and II probes, and dubbed the extraordinary disk of mottled orange "the great pizza in the sky." But Shannon had never heard of any pizza being cooked in the way this one had.
Orbiting through a plasma flux of mean particle energies corresponding to 100,0000 Kelvin sustained by Jupiter’s magnetic field, the satellite acted as an enormous Faraday generator and supported internal circulating currents of five million amperes with a power dissipation of a thousand billion watts. And as much energy again was released inside it as heat from tidal friction, resulting from orbital perturbations induced as Europa and Ganymede lifted Io resonantly up and down through Jupiter’s gravity. This amount of electrically and gravitationally produced heat maintained large reservoirs of molten sulfur and sulfur compounds below the moon’s surface, which eventually penetrated upward through faults to explode into the virtually zero-pressure of the outside. The result was a regular succession of spectacular volcanoes of solidifying sulfur and sulfur-dioxide frost that ejected at velocities of up to a thousand meters per second, and sometimes reached heights of 300 kilometers or more.
Shannon was looking at a view of one of those volcanoes now, sent back from a probe on Io’s surface. It had taken the mission’s engineers and scientists more than a year of back-to-the-drawing-board experiences to devise an instrumentation package and shielding method that would function reliably under Jupiter’s incessant bombardment of radiation, electrons, and ions, and Shannon had felt an obligation to be present in person to observe the results of their eventual success. Far from being the chore he had expected, the occasion had turned out an exhilaration and served as a reminder of how easy it was for supreme commanders of anything to allow themselves to become remote and lose touch with what was happening in the trenches. In future, he thought to himself, he would make a point of keeping more up to date on the progress of the mission’s scientific projects.
He remained in the command center discussing details of the probe for a full hour after he was officially off duty, and then at last excused himself and retired to his private quarters. After a shower and a change of clothes he sat down at the desk in his stateroom and interrogated the terminal for a listing of the day’s mail. One item that had come in was qualified as a text message from Vic Hunt at Navcomms Headquarters. Shannon was both pleasantly surprised and intrigued. He had had many interesting talks with Hunt during the latter’s stay on Ganymede, and didn’t perceive him as being somebody with much time for idle socializing, which suggested that something interesting was afoot. Curious, he keyed in a command for Hunt’s message to be displayed. Five minutes later he was still sitting there staring at the message, his brows knitted in a mystified frown. It read:
Joe,
To avoid any further cross words on this subject, I looked for some clues in the book you mentioned and came across some references on pages 5, 24, and 10. When you get down to sections 11 and 20, it all makes more sense.
How they got 786 is still a puzzle.
Regards
Vic
Not a word of it meant anything to him. He knew Hunt well enough to be reasonably sure that something serious was behind the message, and all he could think of was that Hunt was trying to tell him something highly confidential. But why would Hunt go to this kind of trouble when UNSA possessed a perfectly adequate system of security codes? Surely it wasn’t possible that somebody could be eavesdropping on the UNSA net, somebody equipped with enough computer power to render its protective measures unreliable. On the other hand, Shannon reflected soberly, the Germans had thought exactly that in World War II, and the British, with their "Turing Engine" at Bletchley, had been able to read the complete radio traffic between Hitler and his generals, frequently even before the intended recipients. Certainly this message would mean nothing to any third party even though it had come through in plain English, which made it appear all the more innocuous. The problem was that it didn’t mean anything to Shannon, either.
Shannon was still brooding about the message early the next morning when he sat down for breakfast in the senior officers’ dining quarters. He liked to eat early, before the captain, the first navigation officer, and the others who were usually on early shift appeared. It gave him time to collect his thoughts for the day and keep up with events elsewhere by browsing through the Interplanetary Journal—a daily newspaper beamed out from Earth by UNSA to its various ships and installations all over the solar system. The other reason he liked to be early was that it gave him an opportunity to tackle the Journal’s crossword puzzle. He’d been an incurable addict for as long as he could remember, and rationalized his addiction by claiming that an early-morning puzzle sharpened the mental faculties in preparation for the demands of the day ahead. He wasn’t really sure if that were true, and didn’t care all that much either, but it was as good an excuse as any. There was nothing sensational in the news that morning, but he skimmed dutifully through the various items and arrived gratefully at the crossword page just as the steward was refilling his coffee cup. He folded the paper once, then again, and rested it against the edge of the table to scan through the clues casually while he felt inside his jacket for a pen. The heading at the top read: JOURNAL CROSSWORD PUZZLE NUMBER 786.
Shannon stiffened, his hand still inside his jacket, as the number caught his eye. "How they got 786 is still a puzzle" replayed itself instantly in his mind. Every word of Hunt’s mysterious message had become firmly engraved by that time. "786" and "puzzle" both appearing in the same sentence. It couldn’t be a coincidence, surely. And then he remembered that Hunt had been a keen crossword solver too in his rare moments of free time; he had introduced Shannon to the particularly cryptic puzzles contained in the London Times, and the two of them had spent many a good hour solving them over drinks at the bar. Suppressing the urge to leap from his chair with a shout of Eureka!, he pushed the pen back into his pocket and felt behind it for the copy of the message tucked inside his wallet. He drew out the sheet of paper, unfolded it, and smoothed it flat on the table between the Journal and his coffee cup. He read it once again, and the words took on a whole new light of meaning.
Right there in the first line it said "cross words," and a little further on, "clues." Their significance was obvious now. What about the rest of it? He had never mentioned any book to Hunt, so that part had to be just padding. Presumably the numbers that followed meant something, though. Shannon frowned and stared hard at them: 5, 24, 10, 11, and 20. . . . The sequence didn’t immediately jump out and hit him for any reason. He had already tried combining them in various ways and gotten nowhere, but when he read through the message again in its new context, two of the phrases that he had barely noticed before did jump out and hit him: ". . . came across . . . " associated with 5, 24, and 10, and immediately after: ". . . get down to. . . ," associated with 11 and 20, had obvious connotations to do with crosswords: they referred to the across and down sets of clues. So presumably whatever Hunt was trying to say would be found in the answers to clues 5, 24, and 10 across, and 11 and 20 down. That had to be it.
With rising excitement he transferred his attention to the Journal. At that moment the captain and the first navigation officer appeared in the doorway across the room, talking jovially and laughing about something. Shannon rose from his seat and picked up the Journal in one movement. Before they were three paces into the room he had passed them, walking briskly in the opposite direction and tossing back just a curt "Good morning, gentlemen," over his shoulder. They exchanged puzzled looks, turned to survey the doorway through which the Mission Director had already vanished, looked at each other again and shrugged, and sat down at an empty table.
Back in the privacy of his stateroom, Shannon sat down at his desk and unfolded the paper once more. The clue to 5 across read, "Find the meaning of a poem to Digital Equipment Corporation (6) ." The company name was well known among UNSA and scientific people; DEC computers were used for everything from preprocessing the datastreams that poured incessantly through the laser link between Jupiter and Earth to controlling the instruments contained in the robot landed on Jo. "DEC"! Those letters had to be part of the solution. What about the rest of the clue? "Poem." A list of synonyms paraded through Shannon’s head: "verse" . . . "lyric" . . . "epic" . . . "elegy." They were no good. He wanted something of three letters to complete the single-word answer of six letters indicated in the parentheses. "Ode"! Added to "DEC" it gave "DECODE," which meant, "Find the meaning of." Not too difficult. Shannon penned in the answer and shifted his attention to 24 across.
"Dianna’s lock causes heartache (8)." "Dianna’s" was an unmediate giveaway, and after some reflection Shannon had succeeded in obtaining Di’s tress (lock of hair), which gave heartache in the form of "DISTRESS."
10 across read, "A guiding light in what could be a confused voyage (6)." The phrase "could be a confused voyage" suggested an anagram of "voyage," which comprised six letters. Shannon played with the letters for a while but could form them into nothing sensible, so moved on to 11 down. "Let’s fit a date to reorganize the experimental results (4,4,4)." Three words of four letters each made up the solution. "Reorganize" looked like a hint for an anagram again. Shannon searched the clue for a combination of words containing twelve letters and soon picked out "Let’s fit a date." He scribbled them down randomly in the margin of the page and juggled with them for a few minutes, eventually producing "TEST DATA FILE," which his instinct told him was the correct answer.
The clue for 20 down was, "Argon beam matrix (5)." That didn’t mean very much, so Shannon began working out some of the other clues to obtain some cross-letters in the words he had missed. The "guiding light" in 10 across turned out to be "BEACON," which was in the remainder of the clue and staring him in the face all the time as it had said: ". . . could be a confused." The suggestion of an anagram had been made deliberately to mislead. He wondered what kind of warped mentality was needed to qualify as a crossword compiler. Finally the "argon beam" was revealed as "Ar" (chemical symbol) plus "ray" (beam), to give "ARRAY," i.e., a matrix. Interestingly the answer to the first clue of all, 1 across, was "SHANNON," a river in Ireland, presumably slipped in as a confirmation to him personally.
The complete message with the words placed in the same order as the numbers that Hunt had given now read:
DECODE DISTRESS BEACON TEST-DATA-FILE ARRAY.
Shannon sat back in his chair and studied the final result with some satisfaction, although it so far still told him far from everything. It was evident, however, that it had something to do with the Ganymeans, which tied in with Hunt’s being involved.
Some time before the Shapieron appeared out of the depths of space at Ganymede, the UNSA missions exploring the Jovian moon system had discovered the wreck of an ancient Ganymean spaceship from twenty-five million years back entombed beneath Ganymede’s ice crust. In the process of experimenting with some of the devices recovered from the vessel, Hunt and a group of engineers at Pithead—one of the surface bases on Ganymede—had managed to activate a type of Ganymean emergency transmitter that utilized gravity waves since the propulsive method used by Ganymean ships precluded their receiving electromagnetic signals while under main drive; that was what had attracted the Shapieron to Ganymede after reentering the solar system. Shannon remembered that there had been a suggestion to use that same device to relay the news of the surprise reply from the Giants’ Star on to the Shapieron after its departure, but Hunt had grown suspicious that the reply was a hoax and had vetoed the idea.
That had to be the "Distress Beacon" in Hunt’s message. So what was the "Test-Data-File Array" that Shannon was supposed to decode? The Ganymean beacon had been shipped to Earth along with many other items that various institutions had wanted to experiment with firsthand, and the researchers conducting those experiments usually made a point of sending their results back to Jupiter via the laser link to keep interested parties there informed. The only thing that Shannon could think of was that Hunt had somehow arranged for some information to be sent over the link disguised as a file of ordinary-looking experimental test data purportedly relating to the beacon and probably consisting of just a long list of numbers. Now that Shannon’s attention had been drawn to the file, the way the numbers were supposed to be read would hopefully, with close enough scrutiny, make itself clear.
If that was it, the only people likely to know anything about unusual files of test data coming in from Earth would be the engineers down at Pithead who had worked on the beacon after it was brought up from beneath the ice. Shannon activated the terminal on his desk and entered a command to access the Jupiter Five personnel records. A few minutes later he had identified the engineering project leader in charge of that work as a Californian called Vincent Carizan, who had joined J5 from UNSA’s Propulsion Systems and Propellants Division, where he had worked for ten years after obtaining a master’s degree in electrical and electronic engineering at Berkeley.
Shannon’s first impulse was to put a call through to Pithead, but after a minute or two of further reflection he decided against it. If Hunt had taken such pains to avoid any hint of the subject being interpretable from what went over the communications network, anything could be happening. He was still pondering on what to do when the call-tone sounded from the terminal. Shannon cleared the screen and touched a key to accept. It was his adjutant officer calling from the command center.
"Excuse me, sir, but you are scheduled to attend the Operations Controller’s briefing in O-327 in five minutes. Since nobody’s seen you this morning, I thought maybe a reminder might be called for."
"Oh . . . thanks, Bob," Shannon replied. "Look, something’s come up, and I don’t think I’m going to be able to make it. Make excuses for me, would you?"
"Will do, sir."
"Oh, and Bob . . ." Shannon’s voice rose suddenly as a thought struck him.
The adjutant looked up just as he had been about to cut the call. "Sir?"
"Get here as soon as you’ve done that. I’ve got a message that I want couriered down to the surface."
"Couriered?" The adjutant appeared surprised and puzzled.
"Yes. It’s to go to one of the engineers at Pithead. I can’t explain now, but the matter is urgent. If you don’t waste any time, you should be able to make the nine o’clock shuttle down to Main. I’ll have it sealed and waiting by the time you get here. Treat this as grade X-ray."
The adjutant’s face at once became serious. "I’ll be there right away," he said, and the screen went blank.
Shannon received a brief call from Pithead shortly before lunch, advising that Carizan was on his way up to Jupiter Five via Ganymede Main Base. When Carizan arrived, he brought with him a printout of a file of data, supposedly relating to tests performed on the Ganymean beacon, that had materialized in the computers at Pithead that very morning after coming in from Earth over the link and being relayed down to the surface. The engineers at Pithead had been puzzled because the file header was out of sequence and contained references that didn’t match the database indexing system. And nobody had known anything about any tests being scheduled of the kind that the header mentioned.
As Shannon had anticipated, the file contained just numbers—many groups of numbers, each group consisting of a long list of pairs; it was typical of the layout of an experimental report giving readings of interrelated variables and would have meant nothing more to anybody who had no reason not to accept it at face value. Shannon called together a small team of specialists whose discretion could be trusted, and it didn’t take them long to deduce that each group of pairs formed a set of datapoints defined by x-y coordinates in a 256-by-256 matrix array; the hint had been there in the crossword. When the sets of points were plotted on a computer display screen, each set formed a pattern of dots that looked just like a statistical scattering of test data about a straight-line function. But when the patterns of dots were superposed they formed lines of words written diagonally across the screen, and the words formed a message in English. The message contained pointers to other files of numbers that had also been beamed through from Earth and gave explicit instructions for decoding them, and when this was done the amount of information that they yielded turned out to be prodigious.
The result was a set of detailed directions for Jupiter Five to transmit a long sequence of Ganymean communications coding groups not into the UNSA net but outward, toward coordinates that lay beyond the edge of the solar system. The contents of any replies received from that direction were, the directions said, to be disguised as experimental data in the way that had thus been established and communicated to Navcomms via the laser link.
Shannon was weary and red-eyed due to lack of sleep by the time he sat down at the terminal in his stateroom and composed a message for transmission to Earth, addressed to Dr. Victor Hunt at Navcomms Headquarters, Houston. It read:
Vic,
I’ve talked to Vince Carizan, and it’s all a lot clearer now. We’re running some tests on it as you asked, and if anything positive shows up I’ll have the results sent straight through.
Best wishes,
Joe