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 2011/07/26 06:28 CDT
Pretty movie: Everything in the Saturn system is in motion!
Posted by Jason Perry on 2011/05/13 11:44 CDT
A fresh report was published online yesterday in Science Express on the discovery of a magma ocean beneath the surface of Io. Big news! This is a paper I've been looking forward to seeing for more than year and half.
Posted by Emily Lakdawalla on 2011/02/07 04:35 CST
There is a huge storm that's spreading across so much of Saturn that it's been readily visible even from Earth-based telescopes. Over the past couple of days a couple of new images of Saturn have appeared that show just how enormous the storm is today.