Pioneer 11 swept past Saturn 45 years ago today

Pioneer 11 swept past Saturn 45 years ago today

On today’s date – September 1 – in the year 1979, NASA’s plucky Pioneer 11 spacecraft became the first earthly craft ever to sweep past the ringed planet Saturn. Incredibly, the spacecraft came within 13,000 miles (21,000 km) of Saturn, crossing the plane of the planet’s rings. In the process, Pioneer 11 found a new ring for Saturn – now called the “F” ring – and two new moons. In fact, the spacecraft almost smacked into one of these unknown moons as it soared past.

Passing Saturn – and passing it safely – was an astounding achievement. And indeed, Pioneer 11 was a true pioneer. It went where no earthly spacecraft had gone before.

Generally speaking, Pioneer 11 did what pioneers always do. It laid the groundwork for those that followed. That included the two more sophisticated Voyager spacecraft, which launched from Earth in 1977 and visited Saturn in 1980 and 1981. Part of Pioneer 11’s job was to test a trajectory near Saturn’s rings, to see if it was safe for the upcoming Voyager mission. So, Pioneer 11 passed through the Saturn ring plane, at the same position that the Voyager probes would use some years later. The idea was that – if there were faint ring particles that could damage a probe in that area – mission planners would prefer to let Pioneer 11 take the damage, rather than the Voyagers.

Cassini mission

In addition, Pioneer 11 also preceded the wonderful Cassini mission, which orbited Saturn – weaving among its moons – from 2004 to 2017. Amd Cassini provided unprecedented and spectacular views of Saturn and its rings and moons.

The Voyagers were cutting-edge. And Cassini returned images beyond anyone’s wildest dreams.

But Pioneer 11 paved the way.

48 years ago #Today, Pioneer 10 became the first spacecraft to go beyond the orbit of Saturn pic.twitter.com/ocsJ0Jt9Tu

— Massimo (@Rainmaker1973) February 10, 2024

The 2 Pioneers had different missions

There were two Pioneer spacecraft. The other was called Pioneer 10. Both Pioneers visited Jupiter, and Pioneer 11 went on to Saturn, to investigate its rings and moons.

Scientists said that Pioneer 11 enabled them to get a sense of Saturn’s internal composition. As a matter of fact, Saturn is not very dense. So it’s long been said that, if you could find an ocean large enough to hold it, Saturn would float on water. Pioneer 11 showed Saturn likely has a relatively small core for an outer gas giant world. In fact, with only 10 times Earth’s mass, Saturn was found by Pioneer 11 to be mostly liquid hydrogen.

Pioneer 11 (probably) still sails on

Pioneer 11’s last transmission reached Earth on November 24, 1995. And so the mission has ended. But Pioneer 11 is one of five spacecraft whose trajectories ultimately will carry them out of our solar system. So, unless something has stopped it (highly unlikely!), Pioneer 11 is still sailing outward, away from Earth, into the depths of space.

It’s moving in the direction of our constellation Scutum. Scutum is next to Sagittarius, which is in the general direction of the center of our Milky Way galaxy. The craft will pass near the star Lambda Aquila some four million years from now.

The Pioneers carry plaques

In addition, like the Voyagers, the Pioneers carry a message from humanity to the stars. They each carry a gold-anodized aluminum plaques, showing the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.

Would an advanced race be able to interpret humanity’s message? It’s hard to say. But – like the Voyagers’ golden records – the Pioneer plaques helped raise the consciousness of human beings back on Earth.

Bottom line: Pioneer 11 came closest to Saturn on September 1, 1979.

Read more: Pioneer 11: Watching the Saturn watchers

Pioneer: First to Jupiter, Saturn and Beyond

Visit Cassini spacecraft image Hall of Fame