In July 2008, Robert T. Pappalardo takes the role of project scientist for the Cassini Equinox Mission at Saturn. He will oversee more than 200 scientists, as Cassini enters its fifth year of operation around Saturn. Pappalardo offers his perspective as Cassini moves into its next exciting phase of exploration.
One of the greatest surprises about Cassini's science results is that some of the most extreme predictions have turned out to be correct. The reality is that Titan, the other icy moons, Saturn, and the rings are as spectacularly bizarre as we had hoped in our wildest dreams. Scientists often devise fantastic models of what might exist at a given place -- maybe we hope that we'll find something really exotic. At Saturn, the fantastic and exotic really do exist.
Saturn, its moons, rings, and magnetic environment are more dynamic than we ever expected they would be. With Cassini, we're not just looking at events that occurred in the past; we're watching these things happening before our eyes. Cassini has accomplished the reconnaissance of the Saturnian system, and now in the Equinox mission we can home in on specific targets of greatest interest.
Cassini's found liquid lakes of ethane and methane on Titan! And it rains hydrocarbons, sometimes, we think, torrentially. We can look at Mars and think about what it would have been like to have a fluid flowing on its surface in the distant past. But with Titan, we can go there and observe liquid lakes right now.
A basic tenet of planetary science is that we learn a lot when we compare worlds with similar processes that operate with different initial conditions. Titan is a place that is completely different but strangely, even eerily, similar to Earth. Apparently methane behaves the same way there that water does on Earth. Studying these similar, yet different processes can give us new understanding of how planetary bodies work.
Enceladus is so extremely active that it produces heat that we can actually measure coming off the surface! I look forward to our several returns to the plumes of Enceladus, and the wonderful insights we're going to learn there. My personal research interest is in icy moons, how they work and how they compare, so to me, Enceladus is a real highlight. It's an icy world caught in the act of being geologically active. It is teaching us what makes icy moons tick: especially how tidal heating works, and how important a process it is for shaping icy moons.
At Iapetus, we're still scratching our heads. The "belly-band" bulge of Iapetus, like a self-defined equator, is so bizarre it seems like science fiction. We have ideas that it's related to the early thermal history of the moon, but we don't know for sure yet what it means.
The way moons like Dione, Tethys, and Titan interact with the magnetosphere is unexpected and interesting. In fact, observations of electrons around Rhea suggest that moon has rings! The way the entire magnetosphere around Saturn is shaped like a warped disk is fascinating, and will continue our journey through this magnetic sea so we can better understand it.
New discoveries are making the planet Saturn even more incredible and mysterious. A baffling hexagonal pattern surrounds the north pole. Long-lived storms roil in its atmosphere, revealed by infrared imaging.
The most incredible thing to me about the rings is the fine structure and the interaction between the moonlets and ring particles, the waves and the wakes that form within the rings. The rings mesmerize and astound as a collective thing of beauty. In the Cassini Equinox Mission, we'll be studying them in closer detail, especially as the sunlight moves from the southern to the northern hemispheres of the planet and rings, shining with low lighting angles on the rings.
As we delve deeper into understanding the saturnian system, we can begin to do comparative science with the Jovian system as revealed by the Galileo spacecraft. In the Cassini Equinox Mission, we will be working to learn more about how and why these two gas giant systems are similar, and how they are different.
I am honored and privileged to be carrying the reins, to help guide the next scientific phase of Cassini's exploration. As we move ahead, our goal will be to further tease out answers to new questions that we're just learning to ask.