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.
It's happened again; I went into the Cassini image archive looking for something specific and wound up spending several hours playing with totally unrelated image data. Here are several beautiful images of the rings from the archives.
Cassini flew past Phoebe on June 11, 2004, on its way to entering Saturn orbit. The flyby was almost perfect but overexposure of some images have prevented color mosaics from being produced. Even though Phoebe's body is gray and dull in color, the absence of color images always provoked me. By using VIMS data, I have now produced color mosaics.
Our own Dr. Bruce Betts is once again teaching his Introduction to Planetary Science and Astronomy college course online. Come join him.
Earth's polar vortex has been in the American news all week. But we're not the only planet that has one; basically every world that has an atmosphere has a polar vortex. Here are lots of pretty pictures and animations of polar vortices.
Europa remains a top priority for a future mission to explore whether it could host life. While the Europa Clipper mission, remains the current front runner, a senior NASA manager has suggested that the agency may look at still lower cost options. Van Kane looks at what those options might be.
It's time to reassess Europa exploration, past, present and future. The Destination Europa! session at AGU, inspired by the eponymous website and movement, didn't take exactly that message as its theme, but it's what I got from the presentations. What an ELECTRIFYING meeting this has been for Europa exploration!