Jovian Planets Rulers of the Solar System
Properties • Most of Jupiter and Saturn and about half of Uranus and Neptune are made of Hydrogen and Helium
Energy • With no surface, no surface modification processes • No craters • No volcanoes • No tectonics • No erosion • These are big planets • Big planets have lots of internal energy • With no endogenic surface processes, where does the energy go?
Bands • Differential rotation – poles take longer to rotate than equator
Planetary Rings • All the “Jovian planets” have rings • These are not solid, but composed of millions of tiny particles of ice and dust • Rings have structure: gaps and spokes
Planetary rings – Why? • Left to itself, a ring will slowly spread out due to gravitational interactions • Rings are bounded by the stronger gravity of larger bodies: The planet itself and some of the larger and nearby moons • Some bounds are due to gravitational resonances, others due to the direct action of sheparding satellites • The origin of the rings is unknown – either a failed satellite or a broken satellite • A reason is known: the tidal stability limit at 2.5 times the radius of the body. Interior to this, 2 touching particles will be pulled apart by the planet’s gravity • Why don’t inner planets have rings? Gravitation perturbations by the Sun will cause any small particles to spiral into the planets on a relatively short time scale.