5 NASA Spacecraft That Are Leaving Our Solar System for Good

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Most of these interstellar spacecraft carry messages intended to introduce ourselves to any aliens that find them along the way.
For millennia, humans have gazed up at the stars and wondered what it would be like to journey to them. And while sending astronauts beyond the solar system remains a distant dream, humanity has already launched five robotic probes that are on paths to interstellar space.

Each of these craft was primarily designed to explore worlds in the outer solar system. But when they finished their jobs, their momentum continued to carry them farther from the Sun. Astronomers knew their ultimate fate was to live among the distant stars. And that's why all but one of these spacecraft carries a message for any extraterrestrial intelligence that might find it along the way.

Pioneer 10 flies past Jupiter as the first mission to the giant planet.(Credit: NASA on the Commons (Flickr))

Pioneer 10 and Pioneer 11

In 1972, NASA hadn't even finished sending Apollo astronauts to the Moon yet when it started launching the first missions that would ultimately wind up in interstellar space. That wasn't the end goal though. Pioneer 10 and 11 were primarily intended to do humanity's first major reconnaisance of other planets in our solar system.

Pioneer 10 achieved the first flyby of Mars, the first trip through the asteroid belt, and the first flyby of Jupiter. And the secret to its success was nuclear power. No NASA spacecraft had ever launched with a nuclear-powered electrical source before. So, after Pioneer 10 passed Jupiter in 1973, it still had ample power to keep going. In fact, the mission continued to communicate with Earth for a total of 30 years, rather than the 21 months NASA initially planned for.

Pioneer 11 saw similar success. It made a flyby of Jupiter in 1974 before becoming the first mission to ever encounter Saturn in 1979. Pioneer 11 revealed what the ringed planet is made of, as well as identified new moons and a new ring around the gas giant.

The Pioneer plaque is a gold-anodized aluminum plate with these images engraved onto it. (Credit: NASA Ames Research Center)

And while engineers might not have banked on Pioneer 10 or Pioneer 11 lasting quite so long, scientists were always aware the probes' paths would usher them out of the solar system. And that's why they equipped them both with special plaques designed to introduce their creators, as well as show their paths through space. (However, because Pioneer 11 was redirected past Saturn after launch, its plaque is inaccurate.)

The identical Pioneer plaques show a nude man and woman along with an orbital diagram of our solar system. NASA no longer gets signals from the Pioneer spacecraft, but if extraterrestrial life ever finds them, they should be able to deduce what our species looks like and where we're from.

Voyager 1 and Voyager 2

The Voyager golden record (left) is a 12-inch gold-plated copper disc. It's covered with aluminum and electroplated with an ultra-pure sample of uranium-238. (Credit: NASA)

Half a century ago, NASA built its two identical Voyager spacecraft to capitalize on a rare alignment of the outermost planets that only happens once every 175 years. Jupiter, Saturn, Uranus and Neptune were perfectly placed, allowing scientists to chart a course that would send the spacecraft by each of these gas giants. That path also meant that, after they'd completed their tour of our solar system, both Voyager 1 and Voyager 2 would continue into interstellar space.

Voyager 1 launched…
Eric Betz
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