Probes to the Outer Planets


Pioneer 10 was the first spacecraft to penetrate the asteroid belt between Mars and Jupiter and travel to the outer regions of the solar system. It returned the first close-up pictures of Jupiter, measured the temperature of Jupiter's atmosphere, and mapped its magnetic field. Pioneer 11 flew past Saturn and its moon Titan in 1979 during which the first close-up images of that planet and its rings were radioed to Earth. Pioneer 11's visit was followed by those of Voyager 1 and 2. In 1986, four and one-half years after visiting Saturn, Voyager 2 made the first close-up survey of Uranus. The Voyager 2 mission provided more information about Uranus and its moons than had been gathered since the planet's discovery. Uranus was previously thought to have nine rings. Voyager 2 revealed eleven rings. Voyager 2 completed its twelve year tour of the solar system with a visit to Neptune and its moons.

Pioneer at Jupiter
Pioneer at Jupiter

In 1989, Galileo was launched to examine Jupiter and its four largest moons. Galileo transmitted images of Jupiter's moon Europa which indicated that water may have existed, and might still exist, beneath Europa's crust. Other Galileo findings include new information about Jupiter's Great Red Spot and images of an eruption on Jupiter's moon Io. The probe took samples of Jupiter's atmosphere as it plunged into the gas giant planet in 2003.

On October 15, 1997, the plutonium-powered Cassini probe began what was anticipated to be a 7 year, 2 billion mile voyage to Saturn. Cassini was the largest, most complex and most expensive interplanetary probe launched to date. The spacecraft went into orbit around Saturn in July 2004, and was expected to observe the planet, its ring system, and many of its moons for at least 4 years. As of 2015, it is still going strong! Cassini will continue observing storms, spokes, lakes, geysers, and more in the complicated Saturn system until it plunges into the planet in 2017.

NASA's New Horizons probe launched on Jan. 19, 2006; it swung past Jupiter for a gravity boost and scientific studies in February 2007, and conducted a months-long flyby investigation of Pluto and its moons in Summer 2015. As part of an extended mission, the spacecraft is expected to continue flying into the Kuiper Belt to examine icy mini-worlds in that vast outer region of our solar system.


The StarChild site is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), within the Astrophysics Science Division (ASD) at NASA/ GSFC.

StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator: J.D. Myers
Responsible NASA Official: Amber Straughn