Suddenly a dozen inexplicable oddities about the Jovian radiation belt made sense. Its exaggerated intensity and the sulfuric emissions recorded by ultraviolet instruments were the result of sulfur ions blasted into it by Io. Geologists now had an explanation for the moon’s weird colors, hot spots, and gaseous bubbles. Instead of impact craters, Io had massive calderas. Io was nothing like Earth’s Moon, inert and cold. It was far removed from the dead bodies expected to litter the outer solar system, far distant from what theory had predicted. Subject to Jupiter’s immense tidal bellows, Io warmed, melted, and blew off eruptions of sulfur that entered into and altered the magnetosphere. At Io the hard and soft geographies of the solar system collided with a display of planetary fireworks.
Such scenes may have been what researchers secretly hoped for, but it was not what they had expected. After Io, they sensed they could only anticipate surprise. They knew the mission had become a true voyage of discovery.
That the iconic image should be a volcano seemed particularly apt. Throughout Europe’s half-millennium expansion, volcanoes had been a constant feature, both as a practical referent and as a symbolic emblem of exploration. Volcanoes guided and inspired, and became themselves prime objects of inquiry. They can serve as a useful index for the Three Ages.
The shipborne First Age traveled from island to island, and the critical isles were almost all volcanic. The Atlantic isles that served both Portugal and Spain were volcanoes: Madeira, Cape Verde, the Azores, and especially the Canaries. So were their destinations, the East and West Indies. There were some notable exceptions, such as the Bahamas, where Columbus first made landfall, and those critical offshore isles that so often served as protected ports of call. But the Antilles were a chain of larger and smaller volcanoes, as were the fabled Moluccas. The very Spice Isles themselves—Ternate, Ambon, Tidor, Banda—were active volcanoes. Between them the twin peaks, Tenerife and Ternate, port of embarkation and port of destination, defined the passage to the Indies.
After Spain finally conquered the Canaries, Tenerife’s Pico de Teide became the tallest peak in Europe, a land’s end and a point of departure for far-voyaging mariners. The isles governed the oceanic routes west; they served as both an economic and an intellectual entrepôt for receiving and disbursing the gathered flora and fauna of Europe, Africa, Asia, and the Americas; they were the proving ground for Spanish colonization, and for the naturalists who would, over centuries, replace missionaries and conquistadors; the islands served as a standard reference by which to compare what explorers might discover elsewhere in the world. In particular, Tenerife’s Teide stood as a template, a rite of passage for ambitious adventurers and a scientific stele by which all else beyond Europe might be measured and its meaning deciphered. This was where one left the Old World for worlds both newer and older. What popular lore attributed to Prince Henry’s mythical college of scholars at Sagres belongs in truth to Tenerife.
Even when physically bypassed, Teide persisted as symbol. The role it enjoyed in the First Age for conquest, the Second Age revived for science. “The port of Santa Cruz is in fact a great caravanserai on the route to America and India,” noted Alexander von Humboldt, in this, as in so many matters, the oracle of the Second Age. “Every traveler who writes his adventures begins by describing Madeira and Tenerife, though the natural history of these islands remains quite unknown.” He promptly set out to correct that defect, scaling the mountain and recording its rocks and flora, effectively field-testing the new sciences on its slopes. By celebrating Tenerife in his Personal Narrative, Humboldt fixed its image in the mind of his endless imitators. Then he went further. When he created an atlas by which to compare Earth’s great mountains, he implanted Tenerife at the center, flanked by the Andes and Himalayas, establishing Teide as the standard by which to measure all the others. In 1831 Charles Darwin declared that he “would never rest easy until I see the peak of Teneriffe and the great Dragon Tree.” When he had the chance for his own expedition, he regretted that the HMS Beagle sailed from Madeira, but as it passed by the Canaries, he glimpsed Teide and recited to himself “Humboldt’s sublime descriptions.” Then he went on to find new icons for the era at the Galapagos, another cluster of volcanic isles .80
When Humboldt subsequently climbed Mount Chimborazo in Ecuador, he recapitulated his ascent of Teide in more Romantic style, and through their comparison he began to formulate his grand synthesis of plant geography. Chimborazo shone as the site where Enlightenment met exploration, the summit of Second Age discovery. It replaced Ternate, the Spice Isles, as the vision quest of journeying. The image appealed powerfully to artists, now making their Grand Tours to classical Europe and discovering in Etna and Vesuvius points where ancient history met natural history. Would-be Humboldts relocated Chimborazo wherever they traveled, using it to assert claims of cultural significance. (Heinrich Möllhausen, for example, inserted a Chimborazo, complete with blowing snow on its summit, alongside the Colorado River in the Mohave Desert.) What the padraõ was for the First Age, Chimborazo equivalents were for the Second.
The Third Age, too, has its Möllhausens, keen to establish continuity and parity with previous exploration. A NASA-commissioned painting of a future astronaut exploring party on Mars, for example, featured a Chimborazo looming on the horizon, exactly in the place where it appears so consistently in nineteenth-century renditions. When Arthur C. Clarke imagined his Eden on Mars, in The Snows of Olympus, he set it on Olympus Mons, a real if dormant volcano, and the largest then known in the solar system. He thus combined the iconography of the Great Voyages with the mythology of the Ancients.
That was literature. The eruption of Prometheus on Io was fact. So were the volcanoes, hot vents, black smokers, and dormant seamounts that dappled Earth’s deep oceans and became a defining discovery for the Third Age on Earth. What these features shared was less shape, or lofty panoramas, than geologic dynamism. When Voyager launched, the expectation was still rife that the satellites of the outer planets would resemble those of the inner planets. Like Earth’s Moon and Mars’s Deimos and Phobos, they would be inert masses, cosmographic fossils, left from the eon of planetary origins. Active volcanoes and geysers showed otherwise: they testified to a still-vigorous geology. The moons were not dead lumps, like geologic shards left from the creation and preserved in orbit like museum pieces. They warmed, they moved, they belched. They had their own distinctive histories. They spoke to our times, not just to the solar system’s antiquity. The volcanoes of Io were for space science the Ternates and Teides by which to triangulate the exploration of the interplanetary seas and new worlds beyond.
VOYAGER 2
Now came Voyager 2 to confirm and amplify its twin’s discoveries, and to demonstrate that it could perform agilely enough to warrant flinging itself not only to Saturn but also to Uranus. If the spacecraft had problems, it also, after Voyager 1’s traverse, had acquired some opportunities.
The problems were that its polarimeter was broken, as its twin’s had been, and more seriously, its primary radio receiver was still tone-deaf and balky and could not track an Earth-broadcast radio signal through its Doppler shift. The contact frequency drifted. The DSN found tricks to work around the stickiness, but when connections were good, flight control seized the moment and sent new commands and programs, and understood that communications might blink off at critical times.81
The opportunities were that its trajectory should help shield it from the kind of radiation damage experienced by Voyager 1. At periapsis it would be twice as distant from Jupiter, and if comparable damage did occur, a program was uploaded that would resynchronize clocks hourly and shrink the potential slurring of programs. Two months before closest approach, a new suite of commands adjusted Voyager 2’s sequencing to target topics of supreme interest raised by Voyager 1’s reconnaissance. Specifically, the spacecraft would maintain a ten-hour Io volcano watch, better measure the Jovian torus near Io, listen for whistlers, watch for lightning and auroras while on the plane
t’s dark side, and photograph the Jovian ring, which it would cross twice. It would see the inner moons differently, and most of them much closer. Overall, it would reverse the sequence of Voyager 1’s trek: it would begin with the moons and then cross the planet on its dark side. The new instructions were uploaded in early April.
On April 24, 1979, seventy-six days before periapsis, Voyager 2 officially entered its observation phase. From May 24 to 27 it took long-range photos of Jupiter, now experiencing a different season of weather. On July 2 Voyager first crossed bow shock. Far-encounter commenced on July 4, some 5.3 million kilometers from Jupiter and 921 million kilometers from Earth. As before, the Jovian magnetosphere was malleable, the result of solar winds and uneven eruptions on Io, and Voyager 2 passed in and out of the billowing cloud. By July 5 it had made eleven crossings and photographed Io so that researchers might see how many of the eight identified volcanoes were still erupting. The press, however, was more interested in a space story with stronger human interest, the imminent death plunge of Skylab. The two encounters—Voyager 2’s at Jupiter, Skylab’s at Earth—made a media counterpoint until the space junk fell into the Indian Ocean and onto Australia on July 11. On July 6, with ample media attention, Voyager continued its surveillance of Jupiter’s weather and Io’s vulcanism. The Red Spot alone now demanded a mosaic of six frames.82
Then came the main event. Voyager photographed the Jovian ring and Callisto on July 7. Voyager 2 saw that satellite far more closely and from the opposite side than had Voyager 1, so it seemed a relatively new discovery. A last set of commands went to the spacecraft to direct its imminent near-encounter. On July 8 the final sequence commenced: the ring again and Callisto up close; then, on July 9, Ganymede, Europa, and Amalthea, followed by Jupiter’s dark side and a long farewell scrutiny of Io. Each sighting offered a closer and fresher perspective than with Voyager 1. At closest approach, 3:29 p.m. PDT, Voyager 2 came within 206,000 kilometers of Jupiter and sped around the giant at 73,000 kilometers per hour, more than ten times the muzzle velocity of a .38 special.
The views were again stunning, and startling. Callisto appeared to be the most densely cratered object known. Ganymede was a geomorphic breccia of craters, grooves, ejecta blankets, and fissures. Europa—“a sort of transition body” between the solid-silica Io and the icy Ganymede and Callisto—was perhaps the most bizarre, because for all its surface crinkling, it was as smooth as a billiard ball. Larry Soderblom noted how unlike these bodies were from the realm of the inner planets, and then listed the observed superlatives: “Included in the Jovian collection of satellites are the oldest (Callisto), the youngest (Io), the darkest (Amalthea), the whitest (Europa), the most active (Io), and the least active (Callisto). Today we found the flattest (Europa).” Voyager’s sequel had matched its original. Even now adulation mingled combustibly with anticipation about what Voyager might achieve. NASA associate administrator for space science, Tim Mutch, championed Voyager as “a truly revolutionary journey of exploration” and exulted that, when “the history books are written,” these times would be recognized as a “turning point.”83
Yet much remained to do even at Jupiter, and Voyager 2 was at a critical turning point of its own, a long, complex trajectory correction, timed with periapsis, that would hurl the spacecraft to Saturn, always an anxious maneuver. The episode became yet more awkward after Jupiter’s radiation, far more intense than anticipated, damaged the already troubled radio receiver. On the evening of July 9, radio contact ceased, and engineers scrambled to reconnect before the scheduled course correction. Happily, the intricate commands had been previously uploaded on July 6, when contact was clear and before bursts of radiation had upset the temperamental receiver. At closest encounter, Voyager’s thruster rocket began a seventy-six-minute burn calculated to maximize the gravity-assist acceleration. The combined momentum would save ten kilograms of hydrazine, and with it, the capacity to tack and steer around Uranus. Meanwhile, the instrumental recording and imaging raged on. The dark-side observations chalked up marvel upon marvel, sighting the ring, auroras, lightning, and a revealing volcano watch on Io. The forward scatter that made the Jovian ring luminous, however, was nothing compared to the foreshadowing that made nearly every mind feverish with anticipation.
Both Voyagers were sprinting to Saturn. But even as it departed, Voyager 2 left a legacy akin to Voyager 1’s iconic image of Io in eruption. Careful analysis revealed a new satellite, a body closer than Amalthea and apparently associated with the ring. It was named Adrastea. Jupiter acquired its fourteenth known moon, and Voyager had discovered another world.
Others would follow.84
ISLANDS
The idea of a New World was a late concept, first broached around 1511 by an Italian humanist in the service of Spain, Peter Martyr, and subsequently consolidated in his posthumous De Orbe Novo (1530). What Europe’s marinheiros discovered in practice were islands. The equivalents in “this new ocean” of space were moons.
The Great Voyages between Old and New worlds was most typically a voyage between islands, or from archipelago to archipelago. Those isles were portal, way station, sanctuary, and fortress. Points of departure—Madeira, the Canaries—had their counterpart in offshore islands from São Tome to Hispaniola or in seaports that had the properties of near-islands, such as Al Mina, Goa, Zanzibar, and Mombasa. The Indies, East and West, are a concourse of islands. Even in the seventeenth century, the Spanish monarchy proclaimed the Canaries, located at a triple junction between Europe, Africa, and the Americas, as “the most important of my possessions, for they are the straight way and approach to the Indies.”85
So, also, islands loomed large in the imagination of explorers, schemers, and cartographers. Fantasy islands, from Atlantis to the Island of the Seven Cities, dotted the Atlantic. Real islands swelled on maps to many times their actual size. Newly discovered isles became the incentive and model for colonization. If uninhabited, like Madeira, they pitted capitalist and colonist directly against the land. If inhabited, like the Canaries, they first required conquest to tame or remove the indigenes, or to smother them by immigration. Island-hopping was progressive as new islands often drafted populations from old; perhaps 80 percent of the Canaries’ population was Portuguese, many following the sugar traffic from Madeira. Islands were potentially profitable estates, less onerous than seizing holdings from the Moors, and they offered ready-made fiefdoms by which to reward enterprising knights. (Sancho Panza mockingly begs Don Quixote to reward him with the governorship of an island.) Continents such as Africa and New Worlds such as the Americas were for the early explorers barriers, not beacons.86
In the Second Age, as sword and cross gave way to rifle and sextant, islands testified to experiments in natural history. As had Humboldt, exploring naturalists honed their skills on Atlantic isles before venturing farther abroad, and like their voyaging progenitors, they did their business on isles as destinations. It was from their journeys among volcanic islands—the Galapagos, for one; the Malay archipelago, for the other—that Charles Darwin and Alfred Wallace independently conceived of evolution by natural selection. Interestingly, Wallace developed his idea while fever-ridden on the Spice Islands themselves, a splendid symbol of how interest in islands persisted while their cultural configuration changed. Even the exploration of Antarctica proceeded mostly from islands (and it was from Ross Island that both Ernest Shackleton and Robert Scott made their separate attempts on the South Pole).
Not least, islands offered competing visions of environmental change. As naturalists spirited around the globe, they tallied the chaotic chronicle of species gained and lost, of lands gardened and gutted, of visions still bright or hopelessly blackened. Islands returned as environmental indices: they represented semi-controlled experiments in the interplay between humanity and nature, with the circulation of species as the measure of nature’s economy. For every relatively untouched isle such as Mauritius, exploring naturalists identified a St. Helena degraded into biotic dust;
for every successfully colonized isle, there was one plunged into ecological chaos; for every Madeira there was a Hispaniola. A summary of an era’s exploring naturalists, Alfred Wallace’s Island Life, was a virtual compendium of colonizing ecology, documenting the often lethal competition between endemic and exotic species.
The Third Age found its isles on the continents in the guise of nature preserves (Robert MacArthur and E. O. Wilson’s The Theory of Island Biogeography replacing Wallace), in the deep oceans in the form of seamounts and hot vents, and in space through the solar system’s dizzyingly diverse satellites. Even as they were disclosed, the seamounts—lush with deep coral, hosting fisheries like diminutive Grand Banks—were being denuded by trawlers. So in the Third Age, as before, there seems to be a precarious balance between discovery and destruction, as stripped seamounts compete with momentarily spared black smokers.
And space? The giant planets resemble the barrier continents of the Great Voyages. They might be coasted or their gaseous bulks occasionally visited by a probe or two, but the real work of mapping hard surfaces and sending robotic explorers (or perhaps humans) would happen on their moons. As with islands, there were a lot of them, and they were different, enough to warrant comparative study. They formed parts of what could readily seem miniatures, talismans, and relics of the solar system. The exploration of the solar system would be primarily an exploration of moons.
For the Ages of Discovery, islands have been symbols as well as sites. They were places for imagination as much as for away teams and probes.
It was onto islands that Europe’s intellectuals projected their social fantasies. From the monastic-styled Utopia of Thomas More to the bustling laboratories of Francis Bacon’s New Atlantis, from the Brave New World of Shakespeare’s Tempest to the tropical Edens portrayed by Pierre Poivre, the yet-undiscovered island was a cameo of cultural ideals. Echoing Homer, who had Odysseus narrate his tale from the isle of Scherie, Camões opens The Lusíads at Mozambique; but narration in medias res commanded less power than the prospect of new lands—new societies, new hopes—that could be lodged only on recently discovered or yet-unvisited islands. Columbus spoke for all such visionaries when he rhapsodized over Hispaniola—and for all scorners, when he failed to implant a society equal to that dream.87
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