Pioneer 10 — first through the asteroid belt
Launched on 3 March 1972, Pioneer 10 was the first spacecraft to cross the asteroid belt and fly past Jupiter. It carries a metal plaque introducing humanity to anyone who might find it.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On 3 March 1972 Pioneer 10 left Cape Canaveral on an Atlas-Centaur rocket. It left Earth at about 52,000 km/h, faster than any human-made object before it. Its destination was Jupiter, which no spacecraft had yet visited. It weighed 258 kg and made its electricity from the heat of plutonium rather than from solar panels, because sunlight near Jupiter is too weak.
On the way lay the asteroid belt, a region between Mars and Jupiter where many small rocky bodies orbit the Sun. No one knew whether dust there would wreck a spacecraft. Pioneer 10 entered the belt in July 1972 and came out safely the following February. Then, on 3 December 1973, it passed about 130,000 km above Jupiter's clouds and took the first close-up pictures of a giant planet.
The radiation around Jupiter was much stronger than expected. Radiation is invisible energy that can damage electronics. Some of Pioneer 10's instruments were harmed, but the spacecraft survived. Thanks to the data it collected, the later Voyager probes were designed with better protection against radiation.
Attached to the spacecraft is a gold-coloured plaque designed by Carl Sagan and Frank Drake. It shows a man and a woman, Earth's place in the solar system, and units of length and time based on the hydrogen atom. The idea is that if someone far in the future finds the probe, they could tell who sent it. The orbit view reproduces the path through the asteroid belt, past Jupiter and out of the solar system.
Mission goals
Pioneer 10 was a pioneer in the plain sense: it went first to see whether the road was safe. Before launch, no one knew whether the asteroid belt could be crossed or whether electronics could survive Jupiter's radiation. Pioneer 10 answered both questions by taking the risks itself. The belt turned out to be mostly empty space, so the probes that followed crossed it without special protection.
As it passed Jupiter, Pioneer 10 used the planet's gravity to gain a great deal of speed. This technique is called a gravity assist. The boost gave Pioneer 10 enough speed to escape the Sun's gravity altogether. Later outer-planet probes, including the Voyagers, also used the gravity of the giant planets to reach distant places.
The plaque left a bigger mark on culture than on science. Its drawing of an unclothed man and woman caused debate in the United States. That debate put a question in front of many people: how should humanity introduce itself? Five years later the Voyager probes carried golden records filled with sounds and pictures of Earth.
Mission chronology and background
Its twin, Pioneer 11, launched in April 1973. It passed Jupiter even closer in 1974 and then, in 1979, became the first spacecraft to fly past Saturn. By going first, the two Pioneers made the Voyagers' journey much easier. Contact with Pioneer 11 ended in 1995.
In 1983 Pioneer 10 crossed the orbit of Neptune and became the most distant human-made object of its time. In February 1998 the faster Voyager 1 took over that title. For years scientists debated the “Pioneer anomaly”, a tiny, unexplained slowing of the probes. A 2012 study found the cause: heat from the spacecraft's power generators escaping more in one direction than another.
The last signal arrived on 23 January 2003 from about 12.2 billion km away, a distance light takes more than 11 hours to cross. Since then Pioneer 10 has travelled on in silence toward Aldebaran, the bright star in Taurus. It will take about two million years to get near it.
Where to see it — sky and simulator
Contact with Pioneer 10 was lost in 2003, so its present position is calculated from its last known orbit. In 2026 it is about 140 AU from the Sun, in the direction of Taurus. One AU is the distance from Earth to the Sun, so the probe is 140 times farther away than that. No telescope can see it.
The orbit view reproduces, in order, the March 1972 launch, the crossing of the asteroid belt, the Jupiter flyby of December 1973 and the path out of the solar system. Follow the probe and speed up time, and the track can be seen bending sharply as it passes Jupiter. In the 3-D interstellar view, Pioneer 10 is marked at its current position near the edge of the solar system, together with Voyager 1, Voyager 2 and New Horizons.
See this for yourself — replay the moment in the orbit view
FAQ
How close did it get to Jupiter?
About 130,000 km above the clouds on 3 December 1973, taking the first close-up pictures of a giant planet.
What is on the plaque?
A man and a woman, units based on the hydrogen atom, the Sun's position marked using 14 pulsars, and a map of the solar system with the probe's path.
Where is it now?
About 140 AU from the Sun in 2026, heading toward Aldebaran in Taurus. With no contact since 2003, this position is calculated.
Is it farther away than Voyager?
No. Voyager 1 overtook Pioneer 10 in 1998, and both Voyagers are now farther away.
Related
- Voyager 1 launch
- Voyager 2 launch — the Grand Tour
- New Horizons launch
- Pioneer 10 — object index
- Jupiter — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.