AMONG THE PLANETS, Jupiter has always been more saturnine than Saturn, a huge, paranoid presence that could have been a contender: at creation, it gathered up almost enough mass to give off its own light. All the planets, at the moment of their birth, were too hot not to cool down, but Jupiter is still cooling down, even now giving off more heat than it takes from the Sun. It has been called "a star that failed," its necklace of moons a sort of second-prize solar system. The "Jovian satellites" are the only ones anywhere to have their own atmospheres (if just barely), battered almost-planets abused by an unhappy almost-Sun. One of the closest, Io, astonished those running the space probe Voyager 1, whose 1979 flyby revealed "gigantic…volcanos spewing debris a hundred miles above [the] sulfur- and lava-strewn surface." Galileo, who first found Io with his brand-new telescope in 1610, had no real idea of its wretchedness. He concentrated on the way it and the three other moons might aid shipboard navigation, and on the rewards that would be coming his way for their discovery. The announcement of these "Medicean Stars" set off an orgy of dynastic self-congratulation, a production of masques and medals to reinforce the Florentine ruling family's self-proclaimed association with Jupiter, first the god and then the planet.
The Medici understood the sphere's vastness, but had little notion of how much actually went on there. Over the next 300 years, as Galileo's telescope was enlarged and refined, man learned to focus in on the planet's swirling bands and girdles, the colors and storms raking the surface of this great gasbag 1,300 times the size of Earth. Since the nineteenth century, astronomers have pondered Jupiter's Great Red Spot, wondering if it might be the dilating birth canal of yet another moon or just the solar system's most enduring hurricane. The White Ovals, 10,000 kilometers or so long, were not discovered until the 1930s, because they didn't exist before that: Jupiter is so changeable, so inanimatedly alive, that the usual question about whether it could support Life, of the organic kind, seems almost too dull to ask.
All our knowledge of the place was nothing compared to what we found out fifteen years ago, when Voyagers 1 and 2 passed it on a grand tour of the outer planets (then favorably aligned in a way that occurs only once every 175 years) and sent back to Earth a series of frighteningly gorgeous television pictures. The Voyagers were beautiful, swan-like sailing ships. This time Leda had gone to Zeus, putting on just Knowledge, not Power. Jupiter itself remained huge and malevolent, more fiercely Greek than judiciously Roman. It still boils with jealousy, and uses the asteroid belt as a first line of defense, something space probes have to get through before the next gantlets they must run, belts of rock and radiation that further dent and discourage them from going nearer the surface.
"Over millions of years," writes Bruce Murray, who from Pasadena's Jet Propulsion Laboratory saw the Pioneer and Voyager spacecraft survive brushes with the planet, "Jupiter's great gravity field domesticates once-pristine comets, reshaping the wild orbits initiated by the original chance fall toward the Sun. Little by little, the mature domesticated comets mimic the orbits of asteroids." But once in a while, sometime every eighty or one hundred or one thousand years (depending on which astronomer you talk to), a comet will find its way toward the gassy skull of Goliath. Within the last century Jupiter has captured at least three comets and made them orbit the planet itself, a particularly humiliating fate for a comet, like the demotion of a coltish ballerina, used to streaking across the whole heavenly stage. Two of these comets are believed to have escaped, but the third and most temperamental is now staging a suicidal rebellion. Two summers ago it came within 10,000 miles of the planet's surface, an act of presumption that provoked Jupiter to tear it into almost two dozen pieces. Since then the fragments have stuck together. Astronomers now routinely compare them to a string of pearls, but these pearls are closer to the bullets in an automatic clip; there is no stopping what they will do sometime during the third week of July, and that is strike the planet, one by one, at 130,000 mph. The same Jovian gravity that once put them in their place will now ensure that they crash with an impact all out of proportion to their size.
THE PEARLS WERE DISCOVERED one night in March 1993 by two astronomers, one professional (Carolyn Shoemaker) and one amateur (David Levy), whose nightly search for comets and asteroids at Palomar Observatory was then being hampered, predictably, by Jupiter. As they recall it: "David had difficulty finding the star on which he would guide the telescope for the eight-minute exposure. Jupiter was close by, and its glare swamped the field of the guiding eyepiece." They finally managed to make the two films of a single field necessary for spectroscopic scanning. Looking at them two days later, on a cold, unproductive afternoon, Shoemaker suddenly saw something peculiar, a "squashed" comet. She and Levy called for help to a friend at the Spacewatch telescope at Kitt Peak, Arizona, and that night he called back with a confirmation, describing the comet's "appearance, the multiple nuclei, the tails, and the wings, just as the fourth movement of Beethoven's first symphony was wafting through the [Palomar] dome."
Soon afterward, extrapolation of the fragments' path yielded the conclusion that the comet, now named Shoemaker-Levy 9, had only sixteen months of celestial life left. Between the 16th and 22nd of this month the pearls will, as it is now routinely put, cause "the largest planetary impact ever witnessed by humanity." Never have so many telescopes, from the lofty Hubble (finally seeing through its corrective lenses) to patio tripods purchased at Sears, regarded a single astronomical event as will be focusing upon what happens in the southwestern sky this July.
Anticipation rose last fall, when the New York Times's John Noble Wilford wrote that "a rain of cometary debris plowing into Jupiter could blow holes the size of Texas in the thick atmosphere, send out titanic shock waves, kick up showers of dust and radiate flashes of light out among the Jovian moons." The excitement of amateurs has diminished a bit over the past several months, as the pearls began to look smaller and less destructive than they first did. Still, big-ticket telescope time has been allotted across the globe, and the Planetary Society, an organization of over 100,000 buffs, ex-space jocks, and serious scientists, has not lost faith in the spectacular possibilities: they are giving away "Jupiter Watch" T-shirts, setting up a special phone number (1-900-88-IMPACT) with updates, and planning a big viewing party at the U.S. Naval Observatory in Washington.
Since all of the crashes will take place on the planet's far side, revelers will have to wait for Jupiter to come around in its once-every-ten-hours orbit (amazingly fast for its size) in order to assess the damage. The impacts themselves will be left to a variety of space vehicles to detect and photograph: the Galileo probe -- the last of the great missions to the outer planets, launched in 1989 and still heading for its own rendezvous with Jupiter -- will send down its pictures, like a tape-delayed Olympic event. Voyager 2's observations will be a nostalgic effort, a chance for the spacecraft, by now billions of miles beyond the giant planet, to remember its visit to Jupiter fifteen summers before. Its cameras were turned off in 1989, after passing Neptune, but it can still make radio measurements of Shoemaker's impact. Little Pioneers 10 and 11, more than twenty years on the road, decades past their own encounters with Jupiter and traveling past the reaches of the solar system, may still be able to squint back hard enough and notice something.
JUST WHAT THERE WILL BE to see has been, all spring, a matter for conjecture and debate. If the pearls are no longer thought to be the 9-mile-wide monsters first assumed, disagreement about what the smaller pieces will do has, if anything, enhanced professional astronomers' interest beyond what it was. A drive down to the Jet Propulsion Laboratory from Los Angeles (whose springtime yellow smog isn't too different in appearance from what ammonia and methane create above Jupiter's clouds) brought one to a group of scientists trying to predict July's impact even as part of their own cafeteria was closed for earthquake-related repairs. (Comets were considered to be portents of quakes as early as the fifteenth century, and on an April morning, Dr. Ray Newburn, a 38-year JPL veteran cheerfully wearing his comet-decorated tie, pointed to the high pile of scientific journals that had tumbled to the floor of his office at dawn on January 17.)
Will the whole thing disappoint, like the overhyped reappearance of Halley in '86, or the almost-forgotten but then-eagerly-awaited Kohoutek, which turned out, in 1973, to be an extremely damp firework? "It may be," writes astronomer Stephen J. Edberg, "that Jupiter is so, gigantic…it will simply swallow the fragments of the comet's nucleus without so much as a burp." Newburn and his colleague, Dr. Zdenek Sekanina, whose models and forecasts have been changing by the month, say that's unlikely, but Glenn Orton, a Jupiter specialist, does sometimes wonder if the tiger they think they have by the tail won't turn out to be a kitten. He doesn't expect the explosions to create any vast new vortices -- certainly nothing like the Great Red Spot -- but he thinks some of the storms and swirls they engender may last for months. Even if the insulted Jupiter quickly sets itself to rights, repairing its wounds like one of the self-healing targets used by archers, the impacts will still have been extraordinarily forceful. Orton is glad that the event is taking place -- and glad it's happening five astronomical units (the mean distance between the sun and Earth) away from here.
TINY AS THE PEARLS ARE, they would almost certainly wipe out human life, if they were headed this way, and what happens in July will set catastrophists to worrying over what a similar shelling could do to us. The destruction of hundreds of thousands of Siberian acres in 1908 is thought to have been accomplished by a single meteor or asteroid no more than 50 meters wide that never even made land: it exploded five miles up in the atmosphere. Something just a bit larger -- like the asteroid that landed in the Yucatan 65 million years ago and wiped out the dinosaurs -- would surely kick up enough dust to block out sunlight and set off a version of nuclear winter. The only thing that could keep man from being killed by such a cosmic stray bullet is a nuclear weapon of our own, which, properly launched, might deflect or pulverize the invader. You won't find NASA talking openly about this, but as we emerge from the age of Mutually Assured Destruction, it may be levelheaded to keep a bomb or two around, like one of those remaining vials of smallpox virus.
J.L. Lagrange's eighteenth-century theory that comets were actually created by Jupiter -- belched like baseballs from an automatic pitching-machine -- is only one of many that had to give way before we arrived at our current idea of their ingredients: rock and ice and other leftover creational crud that gathered at the far reaches of the solar system, beyond Uranus. Aristotle made a wrong but enduring guess that they were sublunary fireballs and always bad news. (At least for someone: when the weavers of Bayeux put the still-unnamed Halley's comet into the tapestry they made in 1066, they presumably took it as a bad omen for the English, not the French.) Only when Edmond Halley forecast its reappearance in 1758, were comets proved to be governed by physical law. As John C. Brandt and Robert D. Chapman write: "Their orbits could be calculated and their return predicted years in advance…Any rational fear of [them] as signs of disaster or evil should have vanished [then]."
Handfuls of witchy doomsayers -- those expecting not collisions, only imminent bad luck -- remain among us. (One of them in England insists that Shoemaker-Levy is actually Halley, and that its coming destruction is a very bad sign.) But comets have undergone a celestial seachange in their public image. They now delight instead of alarm. Astronomical buffs regard these vulnerable but can-do rovers as heavenly jalopies, capable of astonishing mileage before they fall apart. Ask Dr. Sekanina what attracted him to contemplate them years ago, when he was still a boy in Czechoslovakia, and the first thing he mentions is their size. They are small enough to wrap the mind around, almost human in scale, like the asteroid Ida, just 35 miles long, discovered only last summer to be in possession of its own moon, a single mile in diameter. The tininess of such objects, their moving and enduring within the void, is what enchants, a version of the desert-island or magic-carpet fantasy. In the case of the comets, the tails are, to the beholder, more important than the nuclei emitting them. It is the fiery tresses that let us picture comets doing what they do, and that is move. On the sky's clock-face they sweep like second-hands, while all the other bodies, Jupiter included, proceed too slowly to watch. We take the planets' movements, like the hour-hand's, on faith, but the travels of comets are something we can -- or at least think we can -- see. Comets plot time against space, and their flaming tails remind humans of something they themselves used to do long ago: climb aboard rockets, and set out for new worlds.
"IT WAS AT ROME, on the fifteenth of October 1764, as I sat musing amidst the ruins of the Capitol, while the barefoot friars were singing vespers in the Temple of Jupiter, that the idea of writing the decline and fall of the city first started to my mind." Just as Gibbon never accepted Christ's usurpation of Jupiter's position, remaining in love with all that had declined and fallen, there will be many looking up at the god's planet this July and thinking about how much more lofty and exciting and willful their own heavenly gazing was a quarter-century before. The crash of Shoemaker-Levy coincides exactly with the twenty-fifth anniversary of Apollo XI's voyage, and while the comet's enthusiasts can talk as much as they like about its causing "the largest planetary impact ever witnessed by humanity," that won't change the minds of those who recall a single night in 1969.
"Celestial mechanics" once more means what it used to -- the study of the movement of heavenly bodies -- but for a brief period, still in living memory, it meant men in their flying machines. When the collision occurs this summer, the insult will be not to Jupiter, but to ourselves. Five astronomical units from the sonic boom that no one will hear, we shall be gaping at an event over which we have not the slightest influence. When the Eagle landed safely, it was because Neil Armstrong had just steered his ship away from some rocks it would have foundered upon. (CAPCOM: "Roger, Tranquility. We copy you on the ground. You've got a bunch of guys about to turn blue. We're breathing again.") Even Voyager 2, with no one aboard, survived its post-launch problems and Jupiter's radiation belts because of remote-control human interventions. This July, some may marvel, but no one will turn blue, and there will be nothing to bring home from the event, no more moon rocks to be proffered as diplomatic gifts, as they were twenty-five years ago -- and as Cosimo de Medici II gave duplicates of the telescope through which Galileo discovered Io.
Man goes no more a-roving: it is more than twenty years since he last had his feet governed by another world's gravity. There are, of course, those scientists who say good riddance to his presence in interplanetary space; he was always too clumsy and cost-inefficient and vulnerable an explorer for their taste. The solar system was better left to machines like Voyager, unmanned and indefatigable. "The last twenty-five years have been wonderful," says Dr. Sekanina, as he thinks of their robotic journeys. But even that exploratory era is, he admits, "all over." He laughs when he says this, but one knows what the overstatement means. Each day the big tracking billboard at JPL is updated to show where Galileo and Ulysses are, how far they have traveled from Earth and how long they have to go before reaching Jupiter and the Sun. But what after that? There may yet be a joint venture with the European Space Agency, the Cassini mission to Saturn and one of its moons, and there's talk of a "fast-flyby" mission to Pluto, but Washington's budgetary emphasis, when there's any political interest at all, is always now on better, cheaper, smaller, faster -- and, as nearly as possible, foolproof.
ONE OF THE MANY POSSIBILITIES on Jupiter this July is that the tiniest bits of the Shoemaker-Levy pearls will escape complete destruction and produce a thin ring that keeps orbiting Jupiter. If this happens, they will have met the same fate as the American manned space program, which survives as a round-and-round commuter exercise heading nowhere but home and home again. It is impossible to find any real enthusiasm for the shuttle (or, for that matter, the space station) among those interested in exploration. On this point the manned-space enthusiasts of the Planetary Society express the same basic feelings as the mechanical explorers of JPL. The shuttle, whose approval by Richard Nixon provided the space community with the minimum funding and activity required to continue institutions built up over the previous decade, was, if anything, an "anti-space" decision, says the Society's executive director, Louis D. Friedman. By the time it was launched in 1981, the idea of further manned exploration was essentially dead. "The eighties were terrible," says Friedman. "We didn't go anywhere." The culture moved on to a new self-loathing phase, too embarrassed by its own failures to speak up for the idea of exporting itself to other worlds.
Arthur C. Clarke, in an afterword to the astronauts' official account of their Apollo XI voyage, had predicted longer and longer journeys to more and more places, and the birth of a first human extraterrestrial, before the year 2000. "Anything written about the moon at the beginning of the 1970's," he argued, "will probably look silly in the 1980's, and hilarious in the 1990's." By that time, he was sure a whole human colony would be operating there. Instead, a small collection of manmade junk lies perfectly preserved on the lunar surface, and we stay home, cultivating our own doomed garden and learning to reproduce ourselves in petri dishes. The only serious movement the planet has made, outside its normal heliocentric round, is toward the constellation Virgo, at 425 miles a second, a galactic drift we didn't even realize until recently, when researchers detected a Great Attractor 300 or more million lightyears away that is guiding the Milky Way in its direction.
"Nobody who's in the space business is pessimistic," says Friedman, who in April was trying to excite himself with the news that the Shoemaker fragments might still be as much as four kilometers wide. But to him and the other Planetarians, a real "pro-space" decision, something to cheer about, would be a commitment to go to Mars. A call to do that was actually made five years ago, on the twentieth lunar anniversary, by the Bush administration. The deafness of the ears hearing it was exceeded only by the shamelessness with which the proposal was made, the date for landing -- 2019, the fiftieth anniversary -- picked by John Sununu for reasons that had more to do with speechwriting than science. The "initiative" was an empty, decadent gesture, as divorced from exploration as the moons of Jupiter eventually were, by the Medici, from science and their condemned discoverer. Our own abandoned moon has been reduced to a rhetorical trope for policy debates. "If we can put a man on the moon" goes the subordinate clause of many a domestic-needs cry -- each of which forgets that, today, we can't put a man on the moon.
Back in 1970, as Clarke looked confidently onward and upward, he also prophesied the eventual uselessness of cities, since "one of [their] main functions will cease to exist, when men anywhere on earth can be, in all but physical fact, in each other's presence at the touch of a button." This part of his wish he is getting. Today he lives in Sri Lanka -- still about as far away as anyone can get -- and keeps in touch by E-mail.
THE ONLY THING WORSE than answered prayers are half-answered ones. The achievement of the fiber-optics revolution without any further outward movement of the species has put the world into a self-regarding frenzy. The planet, which twenty-five years ago had begun to resemble a fountain, launching itself in small streams into the void, now looks and sounds like an autistic hive of ever more self-stimulating chatter. Enthusiasts of the information superhighway go on about it with wide-eyed cheer, oblivious to the fact that it leads only back to man's own garage. Typical is a piece by William E. Halal ("The Information Technology Revolution") in the July-August 1992 number of the Futurist. Writing about the "knowledge-based social order" that links all information machines into "one seamless whole," he looks forward to the time, just moments away, when "'computing' will no longer be something one does primarily while sitting at a desk; rather, computers will be ubiquitous. Life will take place in a living landscape of interacting, intelligent machines that help us through our daily chores." One variety of computer chip -- "self-healing" in the manner of Jupiter's surface -- will "police [itself] for errors caused by malfunctioning circuit elements and produce signals that compensate for errors the faulty elements would otherwise cause." Not even machines will ever again need to turn blue. Networks like Prodigy are already fulfilling "what appears to be a large social need" and "electronic universities" (presumably as helpful as educational television turned out to be) are now offering degree programs. Each time a company grabs a piece of the action -- such as last March's announcement that Bill Gates and Craig O. McCaw are forming Teledesic Corporation to "build a $9 billion system with 840 small satellites" -- assurances are sought that the new system will be available on both sides of the tracks, so as not to contribute to a deepening of American class distinctions. No one dares suggest that on a planet already overwired and overpopulated, the best thing to do with the information superhighway might be what we have always done with highways -- run it only through the neighborhoods of the poor.
Vice President Gore extols a "planetary information network" as the "means by which families and friends will transcend the barriers of time and distance," as if these phenomena were inherently anti-human, and as if we weren't actually putting ourselves further in their thrall by making the current chief measure of scientific and cultural progress how quickly and how much we communicate with ourselves. Milton met Galileo long after he had discovered the moons of Jupiter
Through Optic Glass the Tuscan Artist views
At Ev'ning from the top of Fesole
but he carried back from his visit with the by-then banished astronomer an image of mental liberty and true transcendence, one he would use as he set about justifying the ways of God to man. Science led naturally (if ironically) into theology, toward something higher. The science involved in our own new communications leads inward and down, shrinking men for a kind of Fantastic Voyage through their own circuitry. It is a technology of miniaturization, which trumpets a promised land -- Virtual Reality -- whose adjective, though few notice, signifies not heightening but diminution.
Those spooky commercials from MCI make their pitch through stark, solitary images, convincing the viewer that this new world is spacious, a vast new breathing space for the imagination; and interactivity, the Futurist insists, takes us beyond the global village, which was merely the result of mass media, to a situation where "electronically mediated relationships…actually turn the earth into a single global community." In fact, global villagers, like economic refugees, are being herded into a teeming tenement where the noise never stops. Some proclaim a triumphant new individualism, as computer users are liberated from the broadcasting elite; but how much individualism is really involved in the scanning of electronic bulletin boards? Their millions of users are for the most part in search of likemindedness -- confirmational politics and shared fetishes. Stitched inside our caul of satellites and information, not even leaving home to shop, we have begun to choke on our own data. By the time of his death in 1980, even Marshall McLuhan had had it with the global village he incorporated two decades before: "the more information one has to evaluate, the less one knows." In his book Technopoly: The Surrender of Culture to Technology, Neil Postman does debunk the supposed new disk-driven joys in favor of other ways of conquering "loneliness, ignorance, and disorder," but the truth is that we need more of all three, especially ignorance, in the form of new worlds we can be ignorant about. We are smart enough to get to them, but disinclined to go, settling for the occasional upward glance, like this July's, but otherwise content to sit and fatten on the terrestrial couch, talking and informing ourselves to death
IN ITS OWN WAY, of course, the couch is a spaceship. Even if the Great Attractor weren't tugging, we would still have a seat on the great moving globe. As David Hockney once mused:
I guess I hold with Buckminster Fuller's comment, you know, "We are in outer space." The idea that outer space is over there and we're not part of it is silly. We're already journeying throughout the universe. It's like how I can never seem to get interested in space movies, because they always seem to me to be about transport and nothing else. Well, transport is not going to take us to the edge of the universe, but an awareness in our heads might. Transport won't be able to do it; it's like relying on buses. But the Einsteinian revolution, like the Cubist, has already done it. Now we just have to open our eyes and see.
But to relish Einsteinian theory in this way -- trying, like the metaphysical poet, to apprehend thought as feeling -- one would have to pretend that we are content with other abstractions, too: of love, say, or ecstasy; and humans are not made that way. They are not capable of feeling here and there at once, and the urge to go cannot be stilled forever, any more than one can look at the humane, luminous surface of a Hockney painting without eventually wanting to poke through toward what seems to be the missing third dimension. "Transport" may be the perfect, gear-grinding noun for the shuttle, but the problem with space movies, what makes them unsatisfying even for those who want to leave here, is that they are just movies. Perhaps the most hopeful audience-reaction to this summer's zoom-lens films from Jupiter, after the comet has arrived on location, will not be to anything that happens on the planet, but an overdue, irritated realization of who is missing from the screen -- ourselves, all of us, out here in the dark.
Thomas Mallon, whose new novel, Henry and Clara, will be published this August by Ticknor & Fields, is also the author of the novel Aurora 7 (W.W. Norton).