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.
Our latest roundup of Cassini goodies from Saturn includes Pan, a ravioli-shaped moon that orbits inside the planet's ring system.
Amateur image processor Ted Stryk revisited Voyager 1 data of Enceladus and came across a surprise.
Behold: Daphnis, the tiny, 8-kilometer moon that orbits within a ring gap, gently tugging on the edges of the gap to create delicate scallops.
Posted by Steven Hauck on 2016/12/20 10:01 CST
2016 marks the 25th anniversary of the creation of what has become one of the primary venues for the publication of research in planetary science: the Journal of Geophysical Research: Planets. This occasion is a good opportunity to look back at what we have learned in this era of expanded exploration and to try to take a peek at the future.
A week ago Saturday I decided -- against my better judgment -- to tackle this monster of a mosaic. I call it the "Glutton for Punishment" mosaic.
Juno may be staying in its 53.5-day orbit for quite a while. Here's a list of the future dates of the next 20 close approaches to Jupiter if the mission stays in that orbit, as well as the latest, near-final version of JunoCam's "Marble Movie."