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Jovian Planets Jupiter in the IR and visible Cassini 2000 Cassini Chevrons Discussion Why do you think weather patterns on Jupiter can last for centuries, while those on Earth rarely last for more than a few days? Comet Shoemaker-Levy 9 1993 Discussion What do you think caused all these comets to line up in this neat little row? Galileo pictures Discussion The clouds on Saturn are made of the same material as those on Jupiter, methane, ammonium and water. Why are Saturn’s clouds much blander looking than Jupiter’s if the composition of the clouds is so similar? Saturn’s atmosphere Hydrogen Helium Water Methane Ammonia 97% 3% 0.1% 0.2% 0.03% Saturn produces more internal Heat than Jupiter Even though Saturn is less massive and nearly as big as Jupiter, it produces 25% more heat per kg than Jupiter. Also Saturn’s atmosphere has only 3.3% He to Jupiter’s 13.6% although we think the overall composition of the two planets is about the same. Discussion Why do you think Saturn produces more heat per kg than Jupiter and why don’t we see the He in its atmosphere? Where could it have gone? Discussion Saturn’s winds have been clocked at 1100 mi/hr, much faster than Jupiter’s. How can you explain this given that Saturn is twice as far from the Sun as Jupiter. Discussion While weather patterns like Jupiter’s great red spot do appear on Saturn they tend to be short lived. Why do you think this is? Saturn’s tilt Galilean Moons Discussion From Earth the Galilean satellites appear only as points of light, yet before the space age astronomers were able to determine each of the satellites rotation rates and found that they are all in synchronous rotation. How could this be accomplished? Albedo Io Europa Ganymede Callisto Moon Mercury Mars 0.63 0.64 0.43 0.17 0.11 0.12 0.15 Discussion What would you expect the result would be of exposing methane CH4 ice to ultraviolet light? Why do things in the outer solar system, composed largely of ices, often appear very dark? Discussion How did astronomers determine the size of the Galilean satellites before the Pioneer and Voyager flybys and HST? Sizes and mass Io Europa Ganymede Callisto Moon Mercury Mars km 3642 3120 5268 4800 3476 4880 6794 MMoon 1.22 0.63 2.02 1.47 1.00 4.49 8.73 Densities of the Galilean Satellites 1. 2. 3. 4. Io Europa Ganymede Callisto 3.53 g/cm3 3.02 g/cm3 1.94 g/cm3 1.85 g/cm3 Discussion Why do you think the Galilean Satellites get less dense as the distance from Jupiter increases? The orbits The orbits of the inner three Galilean satellites are coupled in a 1:2:4 resonance. The orbital period of Europa is twice that of Io while that of Ganymede is 4 times that of Io. Discussion What do you think the effect of this resonance is on the orbit Io? Discussion Do you think Io had more or less impacts over its history than the Earth’s Moon? Why? Io & the Moon Discussion Io has no impact craters. What does this tell you about the surface of Io? Discussion Io is about the same size as the Earth’s Moon. Why is Earth’s Moon geologically dead while Io is so active? Why didn’t Io cool at the same rate as the Moon did? Tidal Heating Discussion Normally, tidal friction will cause the orbit of the satellite to become more circular with time. Why didn’t this happen with Jupiter’s moon Io?