Topic 6: The Jovian Planets

Reading:

Chapter 8: Jovian Planet Systems

There is a clear distinction between the Terrestrials, Jovians, Rock/Ice planets in terms of their sizes, masses, and densities, compositions, and placement in the Solar System. Another difference is that all of the Jovian planets have extensive satellite and ring systems. On a deeper level, there is also a dichotomy in the properties of the Jovian planets in that we have Jupiter/Saturn versus Uranus/Neptune. See Topic 4 for tables that lay out these differences in more detailed terms.
The cause of the differences between Jupiter/Saturn and Uranus/Neptune is probably due to the timing problem we discussed earlier when we talked about the formation of the Solar System. The reason Jupiter and Saturn are so massive and large is due to the fact that they formed where water ice could exist and thus they were able to grow to large masses rather quickly. Their large masses enabled them to capture the abundant hydrogen and helium gas which explains their composition and their overly large masses. Uranus and Neptune forming slightly farther out in the Solar Nebula, also formed where water ice existed but everything happened more slowly. Before they reached the point where they could capture significant amounts of hydrogen and helium gas, the young Sun ignited became bright, and generated an intense Solar Wind and cleared the gas out of the Solar Nebula which halted the formation process of Uranus and Neptune not allowing them to reach their full glories. Such an event may also contribute to why the most populous extra-Solar planets are mini-Neptunes and super-Earths, planet-types found in our Solar System.
In this part of the course on Jovian planets, we concentrate on a couple of issues. We consider issues involving the formation of the Jovian planets and how some of their major moons, Europa (Jupiter), Enceladus (Saturn), and Titan (Saturn) fit into searches for life outside the Earth. Our aims are two-fold:
(1) We return to our model for the formation of Jovian planets, the core-accretion model. We describe the interiors of the Jovian planets, Jupiter, Saturn, Uranus, and Neptune and then look at recent observational results on Jupiter from Juno and Saturn from Cassini to see how comparisons of our models for the interiors of Jupiter and Saturn fare when compared to data. Such comparisons may show whether the core-accretion model for the formation of Jovian planets needs revision or if it is still good to go.

The Cassini observations were actually of the rings of Saturn. We look at the properties of ring systems and how Cassini was able to use the rings as probes of the interior of Saturn.
(2) We look at the major moons of Jupiter and Saturn and their general properties. In particular, we consider questions of whether Europa and Enceladus are good candidates for searches for LAWKI, and if the Saturnian moon Titan, the moon with the most massive atmosphere, is also a good search candidate for LAWKI .

The questions from Topic 2 bear on our notions of what constitutes the Habitable zone of our Solar System and other extra-Solar planetary systems.