Outer Planets

Jupiter, Saturn, Uranus, Neptune, and Their Rings and Moons

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.

Video: Saturn makes its own drama (with a little help)

Posted by Emily Lakdawalla on 2012/05/22 05:43 CDT | 2 comments

The apparently simple device of running Cassini images together like a flipbook makes for a dramatic movie, especially with the help of well-timed musical cues.

Full Free Intro Astronomy Class Now Online

Posted by Bruce Betts on 2012/05/22 02:57 CDT | 0 comments

Bruce Betts' complete CSUDH Intro Astronomy and Planetary Science class is now available online. Find out how to access it, and go behind the scenes.

Methone, an egg in Saturn orbit?

Posted by Emily Lakdawalla on 2012/05/21 02:58 CDT | 3 comments

Cassini obtained its first high-resolution images of Methone on May 20, 2012. Methone is one of the smallest regular moons of Saturn, having a diameter of only about 3 kilometers. It was the first moon that Cassini discovered, very early in Cassini's mission at Saturn, in 2004.

Space Hangout with Britney Schmidt

Posted by Emily Lakdawalla on 2012/05/09 02:06 CDT | 1 comments

Watch a conversation I had with planetary astronomer Britney Schmidt about Europa and the current state of outer planets exploration! Also, bonus video of an earlier hangout with Robbie Herrick.

In Honor of JUICE, a New View of Europa

Posted by Ted Stryk on 2012/05/07 05:30 CDT | 2 comments

To celebrate ESA's selection of the JUICE mission to Jupiter, Ted Stryk produced a new global view of Europa from Galileo data.

Pretty pictures from Cassini's recent Dione flyby

Posted by Emily Lakdawalla on 2012/05/04 05:44 CDT | 0 comments

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.

Titan, Dead or Alive? A Debate

Posted by Emily Lakdawalla on 2012/05/02 10:32 CDT | 0 comments

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.

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.

JUICE (JUpiter Icy moon Explorer) (thumbnail)

JUICE: Europe's next mission to Jupiter?

Posted by Emily Lakdawalla on 2012/04/18 12:00 CDT | 0 comments

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.

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

Posted by Emily Lakdawalla on 2012/04/16 03:11 CDT | 0 comments

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.