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Outer Planets

Jupiter. Saturn. Uranus. Neptune. Each of these giant planets is the center of its own miniature solar system. Each is spectacularly beautiful and scientifically fascinating, which are reasons enough to explore them. But by studying the giant planets and their rings and moons, we can also learn about the forces that operated during the formation of our own solar system, as well as the origins of the hundreds of new extrasolar planetary systems that we discover every year.

And their moons are worlds in their own right. There are at least 16 outer planetary moons that would be called dwarf planets if they orbited the Sun rather than a planet. Two (Jupiter's Ganymede and Saturn's Titan) are larger than the planet Mercury, and one (Triton) is probably a captured Kuiper belt object.

But it is challenging and expensive to explore the outer planets, and missions to the outer planets take a very long time to develop, fly, and operate. Cassini will be orbiting Saturn until 2017, and Juno will operate at Jupiter from 2016 to 2017. After that, it's not clear if anyone will be sending a followup mission to Saturn or Jupiter or its moons, or an orbiter to survey the Uranus or Neptune systems. And there is a critical shortage of the isotope of plutonium that is needed to generate power for outer planetary missions.

Watch the entire Cassini mission image catalog as a movie

Posted by Emily Lakdawalla on 2015/11/20 09:43 CST | 2 comments

If you were to download the entire catalog of photos taken at Saturn to date by Cassini and then animate them like a flipbook, how long would it take to watch them all pass by? The Wall Street Journal's Visual Correspondent Jon Keegan has your answer: nearly four hours.

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A Day in the Solar System: 28 October 2015

Posted by Bill Dunford on 2015/11/09 07:44 CST | 5 comments

On October 28th, the Cassini spacecraft flew through the geyser plume of Saturn's moon Enceladus. But Cassini was not the only spacecraft operating in the solar system that day.

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Jupiter Weather Report: 2014/15 Apparition

Posted by Leigh Fletcher on 2015/11/05 01:44 CST

A summary of Jupiter's changing face as seen from Earth during its 2014/2015 apparition.

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New Concepts to Explore the Jovian System

Posted by Van Kane on 2015/10/28 08:04 CDT | 2 comments

Last year, NASA’s managers invited the European Space Agency to propose a small spacecraft to explore the Jovian system. Van Kane describes the recently-posted results of ESA's concept studies for two possible missions.

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Filling in the Enceladus map: Cassini's 20th flyby

Posted by Emily Lakdawalla on 2015/10/16 06:19 CDT | 7 comments

A couple of days ago, Cassini flew past Enceladus for its 20th targeted encounter. Cassini has seen and photographed quite a lot of Enceladus before, but there's still new terrain for it to cover.

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Towards a Jupiter Weather Forecast

Posted by Leigh Fletcher on 2015/09/24 08:04 CDT

Trying to keep track of the ever-changing face of Jupiter is a pretty big challenge—its a dynamic world that can fascinate and surprise every time we turn our telescopes towards it.

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Checking in on Uranus and Neptune, September 2015 edition

Posted by Emily Lakdawalla on 2015/09/22 01:28 CDT | 5 comments

There are no spacecraft at Uranus or Neptune, and there haven't been for 30 and 25 years, respectively. So we depend on Earth-based astronomers to monitor them, including Damian Peach.

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IceBreaker: The Search for Life on Mars

Posted by Van Kane on 2015/09/08 09:19 CDT | 3 comments

The IceBreaker mission, proposed to NASA's Discovery program for low-cost missions, would seek out life on the northern plains of Mars.

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Galileo's best pictures of Jupiter's ringmoons

Posted by Emily Lakdawalla on 2015/08/24 07:07 CDT | 4 comments

People often ask me to produce one of my scale-comparison montages featuring the small moons of the outer solar system. I'd love to do that, but Galileo's best images of Jupiter's ringmoons lack detail compared to Cassini's images from Saturn.

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Jupiter's changing face, 2009-2015

Posted by Emily Lakdawalla on 2015/07/24 08:46 CDT | 4 comments

Damian Peach's photo-documentation of Jupiter helps us monitor the giant planet's ever-changing patterns of belts, zones, storms, and barges, during a time when no orbiting missions are there to take pictures.

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