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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.

Pretty pictures from Cassini's recent Dione flyby

Posted by Emily Lakdawalla on 2012/05/04 05:44 CDT

Cassini performed its last of three close encounters with Enceladus for 2012 two days ago, and followed the flyby with some spectacular images of Dione.

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Titan, Dead or Alive? A Debate

Posted by Emily Lakdawalla on 2012/05/02 10:32 CDT

A lively discussion and debate between planetary polymaths Ralph Lorenz and Jeffrey Moore about Titan, hosted by the Denver Museum of Nature and Science, moderated by David Grinspoon.

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Ski Helene?

Posted by Emily Lakdawalla on 2012/04/20 01:01 CDT | 2 comments

I enthused about these Helene images the first time they came down from Cassini, and then forgot about them, and then was thrilled anew a couple of weeks ago when Daniel Macháček posted his version, processed from data published by the Cassini imaging team on April 1.

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JUICE: Europe's next mission to Jupiter?

Posted by Emily Lakdawalla on 2012/04/18 12:00 CDT

The Twitterverse is buzzing this morning with news that the Science Programme Committee of the European Space Agency has recommended that the next large European mission be JUICE, a mission to explore the three icy Galilean satellites and eventually to orbit Ganymede.

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Pretty pictures from Cassini's weekend flybys of Enceladus and Tethys

Posted by Emily Lakdawalla on 2012/04/16 03:11 CDT

Cassini flew past both Enceladus and Tethys on April 14. Here's a cool animation of its approach to Enceladus' plumes, and a pretty global picture of Tethys.

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Pretty picture: Janus and Saturn

Posted by Emily Lakdawalla on 2012/04/04 12:15 CDT

In the last few days as it's rounded periapsis in its current orbit of Saturn, Cassini has taken a lot of great photos of Saturn's moons. One series of photos was taken from pretty close to Janus, a moon about a third the diameter of Enceladus that orbits between the F and G rings. And among those, several were taken with the moon sitting in front of Saturn.

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What Saturn's moons can tell us about comets (Notes from LPSC 2012)

Posted by Emily Lakdawalla on 2012/04/03 05:20 CDT

My notes on a two-part presentation by collaborators Jim Richardson and David Minton about the sizes of things in the Kuiper belt, a story they told by looking at Saturn's moons. How does that work? What connects Saturn's moons to the Kuiper belt is craters.

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Notes from the Lunar and Planetary Science Conference: Making Cassini's radar images prettier

Posted by Emily Lakdawalla on 2012/03/26 02:12 CDT

One of the more exciting talks last week was given by Antoine Lucas about his work with Oded Aharonson "denoising" Cassini radar images of Titan. Cassini's radar images are superior to the camera photos in revealing fine details and topography on Titan's surface, but they do suffer from a random noise component that makes the pictures look snowy. Antoine and Oded have developed a method for removing much of this noise.

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Notes from Titan talks at the 2012 Lunar and Planetary Science Conference (LPSC)

Posted by Emily Lakdawalla on 2012/03/20 02:16 CDT

One of the topics I found most exciting yesterday was a series of talks on Titan's climate. Bob West showed how Titan's detached haze has shifted with time. Zibi Turtle presented about how Titan's weather has changed with these seasonal changes. Jason Barnes followed up Zibi's talk -- which was based on Cassini camera images -- with a study of the same regions using data from Cassini's imaging spectrometer, trying to figure out what was going on with that brightening. Ralph Lorenz talked about rainfall rates on Titan. Jeff Moore asked: what if Titan hasn't always had a thick atmosphere?

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Snapshots From Space Video: Revealing Jupiter's (Mostly) Unseen Treasures

Posted by Mat Kaplan on 2012/03/18 01:46 CDT | 2 comments

Tens of thousands of Jupiter images were taken by the Voyager spacecraft, but relatively few have been processed to reveal their true beauty and wonder. The latest Snapshots video from Emily Lakdawalla explains why.

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