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.
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."
Beautiful new amateur work with 27-year-old Voyager data.
Posted by Björn Jónsson on 2016/09/14 08:00 CDT
A few weeks before the first Juno high resolution imaging, I decided to take a look at Voyager color images at various resolutions, with particular attention to high-resolution mosaics.
Titan's north polar lakes are well-lit by summer sun in these recent Cassini images. Image processing enthusiast Ian Regan shares his recipe for processing the longer-wavelength Titan images into visually pleasing "pseudocolor."
On August 27, Juno soared across Jupiter's cloud tops from pole to pole, with all instruments operating. NASA posted some terrific first results from several of the instruments today. And the JunoCam team released all 28 raw images taken during the close encounter.
It is not easy to observe Jupiter’s moons as more than points of light with Juno, because Juno will never get very close to any of the moons, but as its orbit shifts there will be opportunities to collect data on some of the moons.
NASA announced this afternoon that Juno passed through its first perijove since entering orbit successfully, with science instruments operating all the way. This is a huge relief, given all the unknowns about the effects of Jupiter's nasty radiation environment on its brand-new orbiter.