The Why Files The Why Files --

Voyager 1 and 2: The endless journey continues

Voyager spaceships + 30 years: Long gone, but definitely not forgotten!
When Voyagers 1 and 2 were launched in the late summer of 1977, nobody expected they would still be spitting out data on the distant solar system 30 years later. Their task was to spend four years poking around two giant outer planets -- Jupiter and Saturn.A satellite with a large dish and remote-mounted antenna  floats through space

Two Voyager spacecraft, launched 30 years ago, are headed for interstellar space. Photo: NASA

Since the spaceships were not going to stop, they would make as many photos and measurements as possible, and then continue on their way.

Anything else would be gravy.

And gravy the two Voyagers have delivered, by the bucketful, turning in performances that even the most jaded Ahabian boss would say have "exceeded expectations." At present, Voyager 1 is about 15.5 billion kilometers (9.7 billion miles) from the sun, making it the most distant artificial object. In second place? Voyager 2, at 12.5 billion kilometers out.

Great expectations
(Purists might say that Pioneer 10 is even further away, but nobody has heard from it since 2002, so it's hard to know.) In contrast, both of the aging Voyagers are still returning data across the vastness of space.

Jupiter and Saturn? Been there, done that. Uranus and Neptune? First visits. Rings? Explored them. Moons? Seen them. Weird geysers and volcanoes? Taken their initial portraits. (Jump ahead to a slide show of Voyagers's greatest hits.)

Here's one way to imagine how much difference the Voyagers made: When they were launched while Jimmy Carter was president, many astronomers dismissed the many moons of the giant planets as likely to be cold, battered hunks of rock, much like our moon.

Our sun is a small yellow dot in the middle of two sphere graphics in space
Artist concept of the two Voyager spacecraft as they near interstellar space. The two crafts are exploring space above and below the plane of the solar system. The termination shock and heliopause are two boundaries that mark the sun's waning influence on a region about 10 billion miles distant. Image: NASA/JPL

Hit singles
Not exactly. The exploration that the Voyagers started on moons in the deep solar system now indicates that:

Titan, orbiting Saturn, has an atmosphere rich in organic compounds

Europa, at Jupiter, has a subterranean ocean which some scientists believe could harbor life

Enceladus, at Saturn, has a surface crusted with ice (further observations show the surface is eerily similar to Earth's Arctic Ocean)

Enceladus also has liquid water geysers on its surface, even though it orbits in deep, cold space

Io has eruptions that feed the giant donut of sulfur and oxygen ions circling Jupiter

The planets offered their share of excitement, too. Distant Uranus, for example, turns out to have an atmosphere dense enough to transfer heat from one pole to the other. And unlike most planets, it rotates around a horizontal axis, not a vertical one.

Red sphere pockmarked with bits of black floats in space
Jupiter's satellite Io is one of the most active volcanic bodies in the solar system. Voyager's 1979 snapshot showed the moon in unprecedented detail. Photo: NASA

But it was those moons that really caused excitement back on Earth. "When Voyager started in the early 1970s, there were only one or two team members focused on the satellites," says Ed Stone, a professor of physics at the California Institute of Technology, who has been Voyager project scientist since before the launch. "It was possible they would all look like the moon, with heavily cratered surfaces, but every one is distinct."

The zooful of bizarro-moons, natch, became an irresistible lure for planetary geologists.

Four distinct moons, all varying in make-up and surface type
The strange moons of the solar system provided some of Voyager's most surprising discoveries. Moon photos from NASA

Reporting from Uranus, this is Lee Siegel for Associated Press ...
It wasn't just scientists who got fired up about Voyager. As a science writer for the Associated Press, Lee Siegel covered Voyager 2's meet-ups with Uranus in 1986 and Neptune in 1989. "During 25 years as a reporter, no stories left a bigger impression on me than the Voyager flybys," he wrote us. "I still remember vividly standing in the Jet Propulsion Laboratory press room in the middle of the night and seeing close-up pictures of Uranus, Neptune and especially their strange moons appear before me -- growing by one line of pixels at a time as the data came in on TV monitors. It was an eerie feeling to realize that I, the scientists and other reporters present, were the first people on our planet to see these worlds up close. It was exhilarating."

The rest is yet to come
Whether it's Saturn's rings and moons, or the atmosphere of distant Uranus, Voyager provided the baseline data, and sometimes the only data, on the outer planets, and so the name "Voyager" continues to appear in science journals.

Earth is hard to distinguish against a background of starsBy now, Voyager 1 is three times Pluto's distance from the sun, and exiting the solar system at a million miles a day. For both Voyagers, the planets are ancient history, and with nothing nearby worth seeing, the cameras that made so many headlines have shut down.

Look homeward, spaceship: On Feb. 14, 1990, when Voyager 1 viewed its point of origin from a distance of 4 billion miles, our planet was just a faint blue dot. Photo: NASA

But the Voyagers are not quite done. Having finished with the planets, they are now exploring the region where the sun's influence wanes, and interstellar space begins. This remote locale may be less accessible than math to a moth, but the durable space sisters are measuring solar wind, energetic particles, magnetic fields and radio waves.

Their goal is to learn what happens when a solar system meets a galaxy.

The roots of Voyagers


Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive

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