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In the 1970's, no vehicle had gone beyond the asteroids between Mars and Jupiter, that is until Pioneer 10.

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[♪ INTRO] During the 1960s, humans started exploring our neck  of the solar system neighborhood: The Moon. Mars. Venus.

But to get to the more distant and massive worlds, crafts would need to clear one of space’s boss levels: a cosmic fence of asteroids between Mars and Jupiter. The contender for this level would be  the appropriately named Pioneer 10. NASA’s Pioneer 10 was one in a long line of missions seeking to explore the greater cosmos, but unlike its predecessors, it was headed out into the great frontier: the outer solar system.

To prepare for the long journey, Pioneer 10 was designed to run exclusively on nuclear fuel, no solar panels involved, a first for space crafts. The generator used pellets of Plutonium that released heat as some of the atoms decayed. That heat not only kept the electronics from freezing while it was so far from the Sun, but it was also directly converted into electricity without any moving parts.

And as with every journey, you don’t know who you might find, so Pioneer carried some bling with it: a gold-plated plaque with diagrams for any extraterrestrials to decipher. It was a predecessor to the Voyager golden record. Now that the craft’s tank was full,  Pioneer launched on March 2nd, 1972, using a fancy new three-stage rocket to give it the extra oomph it needed to get all the way across the asteroid belt and to Jupiter.

Zooming off at 52,000 kilometers an hour, it was the fastest object ever to leave earth at the time, reaching Mars’s orbit in just 12 weeks! For reference, today’s Martian robots take about half a year or more to make that same journey. After waving Mars goodbye, Pioneer faced one of its biggest challenges… a seven-month voyage through the dreaded asteroid belt to reach Jupiter.

The treacherous trek is peppered with hundreds of thousands of space rocks, varying in size from pebbles to boulders as large as some dwarf planets. If a stray rock with enough momentum collided with Pioneer, well, the mission would be kaput. And experts estimated there was a 1 in 10  chance Pioneer would suffer serious damage.

During the journey, the spacecraft did encounter some asteroid hits, although fewer than expected. All in all, it was pretty smooth sailing, hinting to researchers that it wouldn’t be too difficult to send more missions through. While traveling through that bumpy road, Pioneer took some pictures of the landscape, capturing Zodiacal light… that’s the light from the Sun that’s reflected off of tiny dust particles floating in interplanetary space.

This made it the first spacecraft to observe it while pointing away from the Sun, confirming that light wasn’t related to Earth. After slipping through the asteroid fence, Pioneer reached its first flyby of our biggest planet, Jupiter, in December of 1973. In addition to snapping some pretty pictures that would go on to win an Emmy, Pioneer collected data on Jupiter’s magnetic field and the massive belts of radiation enveloping the planet.

In fact, the radiation was so strong that scientists blamed it for the only failed bit of data collection during the flyby. And there was serious concern that the radiation would kill a lot of Pioneer’s instruments. Approximately 78 minutes after the closest approach, Pioneer 10 passed behind Jupiter for a radio occultation experiment.

But Pioneer left unscathed. This paved the way for all future missions to Jupiter, like Galileo and Juno, in knowing how much shielding they actually needed. Their success was built on this first solar system road trip.

Other data demonstrated that Jupiter,  despite being called a gas giant, is actually mostly liquid and also more massive than scientists originally thought. But a flyby is just that, and Pioneer just kept zooming along. Jupiter’s gravity adjusted Pioneer’s course, aiming it away from the rest of the gas giants, and vaguely in the direction of the star Aldebaran in the constellation of Taurus.

Later missions would have to continue building up the solar system’s family portrait, like its younger sibling, Pioneer 11, which visited Saturn for the first time, and Voyager 2, which is the only spacecraft to visit all four planets beyond the asteroid belt. But it was not time to relax just yet. Pioneer’s science mission continued, studying the particles streaming through the otherwise empty vacuum of space.

It examined particles being belched out by the Sun and extrasolar cosmic rays creeping into our neck of the galactic woods. Pioneer’s main scientific mission was officially over in 1997, but NASA kept contact with the spacecraft to refine how they could track future interstellar missions. And it just kept going, and going, and going…

Until 1998, Pioneer 10 was the farthest spacecraft from Earth. But Voyager 1 was traveling out of the solar system faster, so it now holds the record. In April of 2002, Pioneer 10 returned its last bit of telemetry data. Its nuclear-powered battery was dying, but the craft had enough juice to send a very faint digital response to Earth’s wave hello.

The following January, it waved back for the last time. A mission that was only supposed to last for 21 months ended up living for over three decades. And hey, in two million years, it’ll make its next flyby as a space-based ghost ship saying a silent hello to the star Aldebaran. Maybe then, that plaque will finally find some readers.

Until then, you can bring Pioneer 10 along on your own journeys with March’s pin of the month! This month’s pin features this space pioneer and it’s available all month at It’s only available in March, so make sure to order yours soon. In April, we’ll have a whole new pin for you. [♪ OUTRO]