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A Reverie for the Voyager Probes, Humanity's Calling Cards

A Reverie for the Voyager Probes, Humanity's Calling Cards

It was 40 years ago, on Aug. 20 and Sept. 5, 1977, that a pair of robots named Voyager were dispatched to explore the outer solar system and the vast darkness beyond. What resulted was nothing less than a reimagining of what a world might be and what strange cribs of geology and chemistry might give rise to life in some form or other. It was a real-life Star Trek adventure, but the crew stayed home, communicating with their two spacecraft through a billion-mile bucket brigade of data bits. New computer programs went one way, and data - including scratchy photos of new landscapes and the whispering moans of interplanetary plasma fields - came back the other way. All of it was being carried out by a robot brain with the memory capacity of an old-fashioned digital watch. The spacecraft had been designed to make what scientists called the Grand Tour, taking advantage of a once-every-175-year planetary alignment. Voyager 1 and Voyager 2 were to use the gravity of the outer planets to slingshot from Jupiter to Saturn, and to Uranus and Neptune, and then beyond the edge of the sun's domain into interstellar space. In the end, only half the tour - to Jupiter and Saturn - was actually approved. But the Voyager crew packed for a much longer journey. When they lifted off 40 years ago, the two spacecraft carried golden records inscribed with pictures and sounds from Earth, greetings from President Jimmy Carter and instructions on how to play it all. The Voyagers would observe the universe, and give something back to whoever might one day find them. The robot emissaries cruised the solar system through presidential administrations, wars and scandals, and the Challenger disaster, which happened as Voyager 2 was pulling away from Uranus. At every planetfall, the crew members, a little older and a little grayer each time, reconvened at the Jet Propulsion Laboratory in Pasadena, Calif., for a weeklong marathon of discovery, a circus of science on the fly. With imagery returned by probes, what had been fuzzy dots in the world's biggest telescopes bloomed into worlds. Back on Earth, some theoreticians claimed to be homing in on a putative theory of everything, an Einsteinian dream of an equation simple enough to be inscribed on a T-shirt. But in space, scientists were finding that such theories were no help against nature's endless capacity to invent and surprise. Each new world revealed by the Voyagers was a head-scratcher. Once upon a time, it was presumed that the moons of the outer planets, so far from the sun and so close to the origins of the solar system, would be boring ice balls, geologically and in every other way dead. But then Voyager 2 spotted volcanoes spraying fountains of sulfur from the surface of Jupiter's innermost moon, Io. On close inspection, Saturn's rings - the jewels of the solar system - dissolved into 10,000 grooves, like a vinyl record's, braided, kinked and patrolled by tiny moonlets. Voyager 1 plumbed a fat, smoggy atmosphere of Titan, where nitrogen and methane rains fall on a frozen slush pile of hydrocarbons and oily lakes, and then headed off toward interstellar space. Voyager 2 cruised on to Uranus, mysteriously tipped on its axis and surrounded by rings that make it look like a bull's eye. That morning the televisions in a hushed newsroom at J.P.L. had Uranus on one screen and the Y-shaped cloud of the explosion on the other. By noon, my newspaper friends had packed their bags and headed for Houston or Cape Canaveral. Voyager 2 went on. By the time it reached Neptune - the gatekeeper of our planetary realm, now that Pluto doesn't count - the engineers at J.P.L. had enlisted antennas around the Earth to listen in unison, catching the trickle of data bits flowing from almost three billion miles away. Chuck Berry, whose music was included on the spacecraft records, came to the lab to play for a Voyager farewell party. There would be one last act. In 1990, as it ascended the void, Voyager 1's crew commanded it to turn its cameras backward and snap a family portrait of the worlds it was leaving forever behind. The Earth appears on this picture as the famous "pale blue dot" in a wash of scattered sunlight, a "mote of dust suspended in a sunbeam," as the astronomer and cosmic sage Carl Sagan later described it. Voyagers' cameras are now turned off, but the probes continue to report back on the conditions in deepest space. In October 2012, magnetic field and cosmic ray measurements indicated that Voyager 1 had reached the edge of the magnetic bubble that the sun extends like an umbrella over the planets, blocking outside radiation. Voyager 1 was in interstellar space, the first human artifact to escape the solar system. It and its twin will go on circling the galaxy, long after it has ceased speaking to us. In the fullness of galactic time, the Voyagers may be found, but by then the human race may be long extinct. The Voyager record might be the only physical remnant, the last lonely evidence that we, too, once lived in this city of stars, among these islands of ice and rock. Back then, we were looking forward to an exploration of space that would go on forever. It was magic, and we were all on the spaceship. Correction: August 24, 2017 An article on Tuesday about the accomplishments of the Voyager 1 and Voyager 2 space missions misstated the date on which the PBS documentary "The Farthest" was broadcast. It was shown Wednesday night; it had not already aired at the time the article was published.

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