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.
Posted by Emily Lakdawalla on 2011/12/21 12:10 CST
When I posted about the really cool Cassini SAR images of Enceladus a few weeks ago, I initially wrote that this was the first-ever SAR image of an icy moon other than Titan. Several people (some readers and two members of the Cassini science team!) corrected that statement: Cassini has performed SAR imaging of other icy moons (including Enceladus) before.
Posted by Emily Lakdawalla on 2011/12/15 11:18 CST
A summary of a new article by Matt Tiscareno about planetary ring systems that reviews the known ring systems of the four giant planets and the prospects for ring systems yet to be discovered.
Posted by Emily Lakdawalla on 2011/12/01 07:22 CST
On the November 6, 2011 flyby of Enceladus -- the third such flyby in just a few weeks -- the Cassini mission elected to take a SAR swath instead of using the optical instruments for once. So here it is: the first-ever SAR swath on Enceladus. In fact, the only other places we've ever done SAR imaging are Earth, the Moon, Venus, Iapetus, and Titan.
Is Europa's ice thin or thick? At chaos terrain, it's both!
Posted by Emily Lakdawalla on 2011/11/02 02:12 CDT
Book Reviews: Otherworldly skies, real and imagined
Posted by Emily Lakdawalla on 2011/10/20 12:35 CDT
Pretty pictures & movies: Eye candy from two recent Cassini Enceladus flybys
Posted by Emily Lakdawalla on 2011/10/07 07:09 CDT
Notes from Day 5 of the EPSC/DPS meeting: Saturn's storm, Phobos, and Lutetia