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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.

30th anniversary images of Uranian moons

Posted by Emily Lakdawalla on 2016/02/02 01:06 CST | 6 comments

January 24 was the 30th anniversary of the Voyager flyby of Uranus. Uranian moons have been on my mind ever since New Horizons sent us close-up images of Charon. On the occasion of the anniversary, Ted Stryk produced latest-and-greatest versions of the Voyager views of these worlds.

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Europa Budget Bulge

Posted by Van Kane on 2016/01/25 07:04 CST

Van Kane explains how the key development for NASA’s mission to Europa will be an agreement on how the agency plans to accommodate the monetary bulge that will come from funding the mission.

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Pretty pictures: Bittersweet goodies from Cassini at Titan, Enceladus, and Telesto

Posted by Emily Lakdawalla on 2016/01/15 02:00 CST | 7 comments

Tomorrow, Cassini will fly by Titan, picking up a gravity assist that will tilt its orbit slightly up and out of the ring plane. That will end what has been a wonderful year of frequent encounters with Saturnian moons.

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JunoCam cruise data, and a look ahead to Jupiter

Posted by Emily Lakdawalla on 2016/01/13 11:13 CST | 2 comments

Juno is now fewer than six months and 100 million kilometers away from Jupiter, and the Juno team is busily preparing for the arrival. Amateur astronomers are supporting them by taking lots of Jupiter photos.

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Capturing the Rhythm of Space: Insights from 47th DPS Meeting

Posted by Deepak Dhingra on 2016/01/07 06:33 CST

The Division of Planetary Science (DPS) Meeting saw many exciting scientific discussions spanning the range of processes on different planetary bodies, as well as their replication in the laboratory and in models.

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A Lander for NASA’s Europa Mission

Posted by Van Kane on 2016/01/05 07:03 CST | 8 comments

While there’s at least eight years until it launches, this has been a pivotal year for developing NASA’s Europa mission.

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Jupiter's Great Red Spot

Posted by Björn Jónsson on 2015/12/07 06:59 CST | 1 comment

On the 20th anniversary of Galileo's orbit insertion around Jupiter, amateur image processor Björn Jónsson shares some of the mission's first images of Jupiter's iconic massive storm.

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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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