pioneer two

Most people have heard of the Voyager space probes–the small unmanned spacecraft that were launched in the late 1970s on twin missions to explore the outer planets of the solar system. In addition to being immortalized in Star Trek: The Motion Picture as the origin of the powerful but misunderstood entity known as “V’Ger,” these spacecraft have their own Twitter handle. But few people remember that the Voyagers weren’t the first probes sent on this sort of mission; a few years earlier a little ship called Pioneer 10 was the very first one to blaze the trail.

The Pioneer probe was quite simple. Basically a fiberglass box containing cameras, magnetometers and radio transmitters, the whole thing weighed only 500 pounds. That’s not a lot to bring on a trip to Jupiter. The craft, designed by defense and NASA contractor TRW, was launched on March 2, 1972. The total cost to build Pioneer 10 and its sister ship, Pioneer 11, was $380 million.

This spunky little ship left Earth’s orbit in a big hurry. Traveling at over 32,000 miles per hour, it became the first man-made object to traverse the asteroid belt. Its main mission was to explore Jupiter, the gas giant planet it reached in November 1973. It took a bunch of pictures and made some interesting discoveries, but I’m more interested in what happened after the Jupiter mission was over. After all, what do you do with a space probe that’s past its prime? By definition you just have to kind of leave it alone.


An image of the gas planet Jupiter, taken by Pioneer 10 in 1973.

Pioneer 10 never stopped moving. Due to the law of inertia, it will continue on its trajectory until it encounters another object–and space is pretty empty. Thirty years ago, on June 13, 1983, Pioneer 10 crossed the orbit of Neptune, the outer planet of our solar system. (Remember, Pluto was “demoted” as an official planet in 2006, putting Neptune back on top). In doing so it became the first man-made object to reach interplanetary space. On March 31, 1997, a quarter century after its launch, Pioneer’s mission was officially closed.

Still, even after it left the solar system, NASA was able to maintain contact with Pioneer for quite a long time.  Even after the turn of the century the probe’s fading signal could still be picked up by the Deep Space Network. NASA would occasionally “call” when its antenna was aligned, just to see if it would “answer.” It did so for the last time on January 23, 2003. At that time the ship was 80 times the distance from Earth as the Earth is from the Sun. After that, Pioneer never answered. Another attempt to pick up its signal was made in March 2006–but it was unsuccessful. NASA thinks it’s still out there, but its power batteries have gone so low that the radio transmitter won’t work anymore.

Few voyages in the annals of human discovery rival the epic odyssey of Pioneer 10. Although no people were there to see it with their own eyes, this little bucket of bolts has extended humanity’s reach literally farther than anything before or since. And it’s ostensible mission–to gather information about Jupiter–was a total success. If $380 million sounds like a lot of money, consider how far Pioneer 10 has traveled and the amazing things it’s seen its lifetime–things that no human being will be able to see in person for decades, if not centuries. This machine has truly gone where no man has gone before, and where no man is likely to go for a very long time.

And it’s still out there. Somewhere in the far reaches of space, this little ship is still going. It’s so small and space is so big that probably no one will ever find it, but if you look up at the night sky in a certain place you might be looking right at it and never know it. Provided it’s not hit by a meteor or ground into powder by interstellar dust, Pioneer 10 will still be flying long after the civilization that build it ceases to exist. That’s a pretty profound thought.