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.
We're now just about 12 hours away from Juno's Jupiter orbit insertion. As anticipation ramps up, NASA has released this sneak peek at JunoCam's approach movie, made of views of Jupiter and its largest moons shot during the final approach, up until about five days ago.
Jupiter is growing in Juno's forward view as the spacecraft approaches for its orbit insertion July 5 (July 4 in the Americas). The mission has released images from JunoCam and sonifications of data from the plasma waves instrument as Juno begins to sense Jupiter.
Today NASA held a press briefing and released a press kit for the impending orbit insertion of the Juno spacecraft. The 35-minute orbit insertion burn is scheduled to begin July 5 at 03:18 UTC (July 4 20:18, PDT). Here's a timeline for events relating to orbit insertion.
Juno will go in to orbit at Jupiter on July 5 (July 4 in North and South American time zones), and it's carrying a camera that's going to take really awesome photos of Jupiter. But you're going to have to be patient. Emily Lakdawalla explains why.
The Voyager data set is a gift to Earth that keeps on giving. This week, I've seen three great new images processed from this old data set.