Everything we know about Jupiter today — from the Great Red Spot to the Galilean moons to the magnetic field — builds on what these four spacecraft saw first. This page tells their stories.
Four NASA spacecraft that made the first flybys of Jupiter in the 1970s. Pioneer 10 reached Jupiter in December 1973 — the first spacecraft ever to fly past an outer planet. Pioneer 11 followed in December 1974, then went on to Saturn. The Voyagers flew past Jupiter in 1979 and gave us the first detailed close-ups, including the discovery of Io’s active volcanoes and Jupiter’s faint ring system.
Search online for “Voyager 1 Great Red Spot” and look at the photos. The first detailed images of Jupiter’s swirling clouds were taken by Voyager 1 in 1979 — nearly 50 years ago. They are still some of the most famous Jupiter pictures ever, and they helped scientists predict what later spacecraft like Galileo and Juno would find.
📋 The four early Jupiter missions at a glance
| Pioneer 10 | Pioneer 11 | Voyager 1 | Voyager 2 | |
|---|---|---|---|---|
| Launched | March 1972 | April 1973 | September 1977 | August 1977 |
| Jupiter flyby | Dec 1973 | Dec 1974 | March 1979 | July 1979 |
| Mission type | Flyby | Flyby + Saturn | Flyby + outer system | Flyby + grand tour |
| Closest pass to Jupiter | About 130,000 km | About 43,000 km | About 349,000 km | About 570,000 km |
| Headed where after? | Out of solar system | Saturn, then out | Saturn, then interstellar | Saturn, Uranus, Neptune |
| Famous extra cargo | Gold plaque | Gold plaque | Golden Record | Golden Record |
| Last signal | January 2003 | November 1995 | Still functioning (as of April 2026) | Still functioning (as of April 2026) |
Pioneer 10 — the first to reach Jupiter
Pioneer 10 was NASA’s first mission to the outer planets. It launched on 2 March 1972 — long before Galileo, before Juno, before any of the modern Jupiter missions. Nobody knew at the time whether a spacecraft could even survive crossing the asteroid belt, let alone reach Jupiter’s intense radiation.
In December 1973, Pioneer 10 made the first close flyby of Jupiter in history, passing about 130,000 km above the cloud tops. Its instruments measured Jupiter’s powerful magnetic field for the first time — confirming what astronomers had suspected for years from radio signals on Earth. It also took the first close-up images of Jupiter and a few of its moons.
Pioneer 10 kept sending signals home for more than 30 years after launch — long after its 21-month primary mission was supposed to end. The spacecraft’s last signal reached Earth in January 2003, from about 12 billion km away. It is still out there, drifting silently through interstellar space.
Pioneer 11 — the first to reach Saturn
Pioneer 11 launched a year after Pioneer 10, on 6 April 1973. It was originally a backup in case anything went wrong with Pioneer 10 — but Pioneer 10 succeeded, so NASA gave Pioneer 11 a more ambitious target. After flying past Jupiter in December 1974, Pioneer 11 used the giant planet’s gravity to slingshot itself toward Saturn.
Pioneer 11 reached Saturn on 1 September 1979 — the first spacecraft ever to visit Saturn. At Jupiter, it came as close as about 43,000 km above the clouds, much closer than Pioneer 10 had managed. It also took the first close-up images of Jupiter’s polar regions, which no spacecraft had photographed up close before.
Pioneer 11’s last engineering data reached Earth in November 1995. Like Pioneer 10, it is now drifting out of the solar system — but in the opposite direction, headed toward the centre of the Milky Way.
Both Pioneer spacecraft carry a gold-coloured metal plaque attached to their bodies. The plaques show a man, a woman, and the location of Earth in the Milky Way galaxy — a kind of “message in a bottle” in case any intelligent life ever finds the spacecraft. The plaques were designed by astronomers Carl Sagan, Frank Drake, and the artist Linda Salzman Sagan.
Voyager 1 — the most famous picture-taker
Voyager 1 launched on 5 September 1977 — 16 days after Voyager 2, even though it had the lower number. (NASA named them in the order they would reach Jupiter, not in the order they were launched.)
Voyager 1 flew past Jupiter in March 1979, coming within about 349,000 km of the cloud tops. Its cameras took the most detailed images of Jupiter that anyone had ever seen — including breathtaking close-ups of the Great Red Spot and the cloud bands. Voyager 1 then used Jupiter’s gravity to slingshot toward Saturn, which it reached in November 1980.
Voyager 1’s big Jupiter discoveries
- Io’s active volcanoes — a JPL navigation engineer named Linda Morabito spotted a strange plume above Io in one of Voyager 1’s photos. It turned out to be a volcanic eruption — the first ever seen on any world other than Earth. Read more about Io →
- Jupiter’s ring system — on 4 March 1979, Voyager 1 took the photo that gave the first direct spacecraft image confirming Jupiter has rings. Before that day, nobody had seen them. Read more about the rings →
- Lightning on Jupiter — Voyager 1 also captured the first lightning ever seen on a planet other than Earth.
- Detailed moon close-ups — Voyager 1 imaged Europa, Ganymede, and Callisto in much more detail than the Pioneers had managed.
Today, Voyager 1 is the most distant human-made object from Earth — more than 25 billion km away as of 2026 (its exact distance changes every day). It crossed into interstellar space (beyond the Sun’s magnetic bubble) in 2012.
Voyager 2 — the grand tour spacecraft
Voyager 2 actually launched first, on 20 August 1977 — 16 days before Voyager 1. It took a different, slower path so that its gravity assist would set it up to visit not just Jupiter and Saturn, but also Uranus and Neptune. It is the only spacecraft in history to have visited all four of the giant planets.
Voyager 2 reached Jupiter in July 1979, about four months after Voyager 1. Its closest approach was about 570,000 km — a bit further than Voyager 1, but with the advantage of seeing Jupiter from a different angle. Together, the two Voyagers built a much fuller picture of the planet than either one could alone.
Voyager 2 then went on to reach Saturn (August 1981), Uranus (January 1986), and Neptune (August 1989) — a tour timed to a once-in-175-years alignment of the outer planets. Like Voyager 1, it is still sending data today from interstellar space.
The Voyagers were timed to take advantage of a rare planetary alignment — a configuration of Jupiter, Saturn, Uranus, and Neptune that allowed a single spacecraft to visit all four using gravity assists. This alignment only happens once every 175 years. If NASA had missed it in the late 1970s, the next chance would not come around until the 2150s. Voyager 2 made it through.
GOLDEN RECORD — a real, gold-plated phonograph record attached to each Voyager spacecraft. It contains greetings in 55 languages, music from around the world, sounds of Earth (whales, thunder, a baby crying, a kiss), and 116 photographs. The record was designed by a team led by astronomer Carl Sagan — a message to any future intelligent life that might find the Voyagers far in the future.
What was the difference between Pioneer and Voyager?
It is easy to mix up Pioneer and Voyager because they all visited Jupiter in the 1970s. But they had different jobs:
The Pioneers were the scouts. They proved that a spacecraft could survive the asteroid belt, reach Jupiter, and measure the planet’s radiation and magnetic field. Their cameras were simple, but their job was to make sure Jupiter was safe to visit — and to tell future missions what to expect.
The Voyagers were the explorers. They launched five years later with much better cameras and instruments, following the trail the Pioneers opened. They gave scientists the first detailed close-up views of Jupiter and its moons, including the discovery of Io’s volcanoes and Jupiter’s rings.
Without the Pioneers proving the journey was possible, NASA would not have risked the more expensive Voyagers.
What the four missions discovered together
By the end of the 1970s, the Pioneers and Voyagers had completely changed what we knew about Jupiter. Here are some of their most important shared discoveries:
- Jupiter’s magnetic field — first measured directly by Pioneer 10 in December 1973. Later refined by Pioneer 11 and the Voyagers. Read more →
- Io’s active volcanoes — spotted by Voyager 1 in 1979, the first active volcanoes ever seen beyond Earth.
- Jupiter’s rings — discovered by Voyager 1 on 4 March 1979.
- Lightning on Jupiter — the first ever seen on another planet, by Voyager 1.
- First detailed images — of the Great Red Spot, the cloud bands, and the four big Galilean moons.
- New moons — Voyager 1 discovered three small inner moons (Thebe, Metis, and Adrastea) that are now known to be the source of the dust in Jupiter’s rings.
- Polar views of Jupiter — first photographed by Pioneer 11 in 1974.
- Mapping the radiation belts — essential for designing every later Jupiter spacecraft, including Galileo and Juno.
When Pioneer 10 launched in 1972, nobody knew if a spacecraft could even survive crossing the asteroid belt. Some scientists thought it would be hit by a fragment and destroyed. Pioneer 10 made it through safely — and so have many spacecraft since. Sometimes science is just about being brave enough to find out.
Where are they now?
After their planetary missions ended, all four spacecraft kept travelling outward. The two Voyagers are confirmed to be in interstellar space; the two Pioneers are silent, but they are still travelling outward on escape paths. Here is where each one is heading:
- Pioneer 10 — last signal January 2003. Silent now, drifting toward the star Aldebaran in the constellation Taurus (it would take about two million years to get there at its current speed)
- Pioneer 11 — last engineering data November 1995. Silent now, drifting toward the constellation Sagittarius (toward the centre of the Milky Way)
- Voyager 1 — still functioning as of April 2026. The most distant human-made object from Earth, in interstellar space, sending data from more than 25 billion km away (its exact distance changes every day)
- Voyager 2 — still functioning as of April 2026. Also in interstellar space, on a different trajectory from Voyager 1
Both Voyagers are slowly running out of power — their plutonium generators are losing energy. NASA has been turning off instruments one by one to extend the mission, so fewer science instruments are operating now than before. Sometime in the next decade or so, the Voyagers will go silent too. But they will keep travelling outward for hundreds of thousands of years.
The Voyagers have left the solar system.
They have left the heliosphere — the Sun’s magnetic bubble — which means they are in interstellar space. But scientifically, the solar system reaches much further out, all the way to the Oort Cloud of comets. The Voyagers won’t leave the solar system completely for tens of thousands of years.
The Pioneer and Voyager missions are a great way to teach scientific patience. Pioneer 10 was designed for a 21-month mission and lasted 30 years. The Voyagers were planned for a 5-year mission and are still operating after nearly 50. Ask students: what does it mean to build something so well that it lasts more than ten times longer than expected? (Excellent engineering, careful use of resources, and creative thinking when things go wrong.)
Frequently asked questions about Pioneer and Voyager
What were the Pioneer and Voyager missions?
Four NASA spacecraft that made the first close visits to Jupiter in the 1970s. Pioneer 10 (1973) was first, followed by Pioneer 11 (1974), Voyager 1 (March 1979), and Voyager 2 (July 1979). The Pioneers were trailblazers; the Voyagers had better cameras and made more famous discoveries.
What was the difference between Pioneer and Voyager?
Pioneer 10 and 11 were scouts. They proved spacecraft could reach Jupiter safely and measured its radiation and magnetic field. Voyager 1 and 2 came later with much better cameras and instruments, giving the first detailed close-up views of Jupiter and its moons.
Are Pioneer 10 and Pioneer 11 still working?
No. Pioneer 11 last sent engineering data in November 1995, and Pioneer 10’s last signal was received in January 2003. Both spacecraft are silent now, but they are still travelling outward through space on escape paths.
Are Voyager 1 and Voyager 2 still sending signals?
Yes, as of April 2026 NASA confirmed both Voyagers were still functioning, though their power is fading and instruments are being turned off one by one to extend the mission. Sometime in the next decade or so, they will go silent.
Which spacecraft was first to reach Jupiter?
Pioneer 10. It made the first close flyby of Jupiter in December 1973 — the first spacecraft ever to visit any of the outer planets.
Who discovered Io’s volcanoes?
A young Voyager engineer named Linda Morabito spotted an unusual plume in a Voyager 1 image of Io in March 1979. It turned out to be an active volcanic eruption — the first ever seen on a world other than Earth.
Who discovered Jupiter’s rings?
Voyager 1, on 4 March 1979. A small team of scientists had convinced the Voyager team to take one extra photograph to check for possible rings. The photo gave the first direct spacecraft image confirming Jupiter has rings, making Jupiter the third planet known to have rings (after Saturn and Uranus).
Are the Voyagers still working?
Yes — as of April 2026 NASA said both were still functioning, sending data from interstellar space more than 25 billion km from Earth. NASA has been turning off instruments one by one to extend the mission, so fewer science instruments are operating now than before. Sometime in the next decade or so, the Voyagers will run out of power and go silent.
What is the Golden Record?
A gold-plated phonograph record carried on each Voyager spacecraft, containing greetings in 55 languages, music from around the world, sounds of Earth, and 116 photographs. It is a message to any future intelligent life that might find the Voyagers far in the future.
What is the Pioneer plaque?
A small gold-coloured metal plaque attached to each Pioneer spacecraft, showing a man, a woman, and Earth’s location in the Milky Way. Like the Voyagers’ Golden Record, it is a kind of “message in a bottle” for any intelligent life that might find the spacecraft.
Why did the Voyagers visit so many planets?
Because of a rare alignment of the outer planets that only happens once every 175 years. NASA timed Voyager 2’s launch to take advantage of it. Voyager 2 reached Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989) — the only spacecraft to ever visit all four giant planets.
Where are the Pioneers and Voyagers now?
All four are heading outward away from the Sun, in different directions. The two Voyagers are confirmed to be in interstellar space and were still functioning as of April 2026. The two Pioneers are silent (Pioneer 10 since January 2003, Pioneer 11 since November 1995), but they are still travelling outward on escape paths. None will reach another star for tens of thousands of years.
Why is Voyager 1 called “1” when Voyager 2 launched first?
NASA named them in the order they would reach Jupiter, not in the order they were launched. Voyager 2 launched on 20 August 1977 and Voyager 1 launched on 5 September 1977 — but Voyager 1 was on a faster trajectory and reached Jupiter four months before Voyager 2.
Quick recap
- Pioneer 10 (launched March 1972) — first spacecraft to reach Jupiter, in December 1973
- Pioneer 11 (launched April 1973) — Jupiter flyby December 1974, then first to reach Saturn in 1979
- Voyager 1 (launched September 1977) — Jupiter flyby March 1979, discovered Io’s volcanoes and Jupiter’s rings
- Voyager 2 (launched August 1977) — Jupiter flyby July 1979, then on to Saturn, Uranus, and Neptune
- Together, they discovered: Jupiter’s magnetic field, Io’s volcanoes, Jupiter’s rings, lightning on Jupiter, and three new inner moons (Thebe, Metis, Adrastea)
- Both Pioneers carry a gold plaque; both Voyagers carry a Golden Record — messages from Earth to the cosmos
- Both Voyagers were still functioning as of April 2026, sending data from interstellar space; both Pioneers are silent but still drifting outward
Want to see what came next? Visit the Galileo orbiter (the first to orbit Jupiter), the Juno mission (what it discovered up close), or the rings and Io pages that the Voyagers helped discover.