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.

Gravity assist

Posted by David Shortt on 2013/09/27 01:30 CDT | 10 comments

With the recent announcement by NASA that the 36 year-old spacecraft Voyager 1 has officially entered interstellar space at a distance from the sun about four times further than Neptune's orbit, and with Voyager 2 not far behind, it seems worthwhile to explore how humans managed to fling objects so far into space.

Europe Will Select Its Next Major Science Mission in November

Posted by Van Kane on 2013/09/25 01:22 CDT | 2 comments

The European Space Agency will announce two major science missions this November, one of which is likely to be devoted to solar system exploration.

Probing Titan's Atmosphere

Posted by Sarah Hörst on 2013/08/26 03:14 CDT | 11 comments

By now I hope that everyone has seen some of the spectacular images of the Saturn system (and especially Titan!) from the Cassini-Huygens mission. However, the measurements that often make my heart race are taken by instruments that reveal Titan in ways that our eyes cannot see.

New Horizons LORRI view of Pluto and Charon

New Horizons: Late in Cruise, and a Binary Ahoy

Posted by Alan Stern on 2013/08/24 09:16 CDT | 2 comments

New Horizons has just completed a summer of intensive activities and entered hibernation on Aug. 20. The routine parts of the activities included thorough checkouts of all our backup systems (result: they work fine!) and of all our scientific instruments (they work fine too!).

Pretty picture: spectacular Saturn and Titan

Posted by Emily Lakdawalla on 2013/08/15 08:04 CDT | 3 comments

A lovely view of the ringed planet and its hazy moon seen from nearly behind them just a few days ago.

Jupiter and Io from Pioneer 10

Posted by Ted Stryk on 2013/08/02 04:25 CDT | 1 comments

This is a parting shot of Jupiter and Io, taken December 5, 1973, by the Pioneer 10 spacecraft, the first to see either world as a crescent.

Movie SciFi With Real Science? What a Concept!

Posted by Mat Kaplan on 2013/07/30 10:14 CDT | 1 comments

This week's Planetary Radio features the new indy film that relies on the best available science to create a thrilling and inspiring human mission to Jupiter's moon.

Jani Radebaugh, Titan Explorer

Posted by Bill Dunford on 2013/07/23 03:47 CDT | 4 comments

Robotic space exploration is human exploration. Meet one of the people behind the machines.

Pretty picture: Looking backward

Posted by Emily Lakdawalla on 2013/07/23 05:03 CDT | 15 comments

Here it is: the view from Saturn of our Earthly home, one and a half billion kilometers away. We see Earth and the Moon through a thin veil of faintly blue ice crystals, the outskirts of Saturn's E ring. Earth is just a bright dot -- a bit brighter than the other stars in the image, but no brighter than any planet (like Saturn!) in our own sky.