Chapter 8 Part 1 The Giants: Jupiter and Saturn

Transcription

1 5th Planet: Jupiter the Massive Chapter 8 Part 1 The Giants: Jupiter and Saturn Jupiter is the most massive object in the Solar System (300x bigger than the Earth). It actually weighs as much as all the other planets together. The movie 2010 aside, it is far below the mass needed to begin nuclear fusion and become a brown dwarf star. Jupiter s Vital Stats Jupiter s Clouds It rotates in about 10 hrs and takes 12 years to revolve around the Sun. It has a slightly eccentric orbit and high albedo. The high albedo is due to the beautiful high cloud structures. This closeup pic shows the swirling on the edges as clouds in darker areas sink and brighter ones rise. This happens while the whole atmosphere rotates around Jupiter every 10 hours. Jupiter s Cloud Bands Are Permanent and Changing Jupiter s Great Red Spot One notably long-lived feature is the Great Red Spot, which Cassini first spotted in the 1600s. It seems to be a large, permanent hurricane in this one cloud band. Over the past 10 years, it has begun to fade slightly, although it is just as big. 1

2 Jupiter in Cross-section We believe that Jupiter is made up of three cloud layers on top of a deep band of hydrogen/helium clouds. Notice that below the clouds, the temp and pressure quickly rise beyond what life could support. Comet Shoemaker-Levy Impact Sites We got more data on Jupiter s cloud structure from a cometary impact in We learned that the winds at the top of the clouds move at about Mach 3! Vital Stats on Galilean Moons Galilean Moon Surfaces Notice that Jupiter s moons are as big or bigger than the Moon and Mercury. They also are as heavy or heavier than the Moon they have iron in their cores that the Moon lacks. They are also as far out from Jupiter as the Moon is from Earth, but rotate much faster! They are set up above moving farther out from Jupiter, beginning with Io. Notice that t as you move out (right), the moons get smoother, grayer and icier Jupiter is a hot and active planet that boils away water. Europa is the only moon that might have life in a liquid water ocean under its icy surface. Cross-Section of Jupiter s Moons Io: Innermost and Volcanic Io is innermost and takes a beating from Jupiter s magnetic field. Jupiter keeps the mantle of Io stirred up and causes numerous gas volcanoes. Io is the most volcanically active place in the Solar System. 2

3 Europa May Have Life The presence of a large, warmish (60s F) ocean of liquid water leads many to believe that this is the most likely spot for life in the Solar System. While it is not likely, l conditions have been constant like this for billions of years and life may exist beneath the ice. There is no atmosphere above it, so life would have to be constrained to the deeper parts of the ocean. Ganymede: Grooved but not Dead Ganymede is the largest moon in the Solar System, but seems like a small planet in makeup. It is not volcanically active, but it does have an iron core and mantle like the Earth. It cooled long ago and now has a covering beneath its dusty surface. The ice heaves and settles producing halfmile high grooves on the surface. Callisto: Frozen at Impact Farthest out is Callisto which bears the scars of large impacts on its icy surface. Too far out for volcanism, Callisto s surface is coated with a shallow layer of ice that highlights past impacts. The largest impact crater, Valhalla, is almost 1500 miles across! Where is Bruce Willis when you need him? Other Moons of Jupiter Jupiter has at least a dozen more moons, but most of them look like lumpy Amalthea (compare to Mars moons, Phobos and Deimos). Jupiter also has a faint ring with small shepherd moons and some smaller moons that look like captured asteroids. Rings Around Jupiter Jupiter also has a faint ring inside the orbit of Io. Since Jupiter is so massive and gravitationally strong, it probably bl absorbed b most of the dust that could have made the rings bigger what we see today is just a hint of what the rings could have been. 6th Planet: Saturn the Ringed With the largest ring system among the planets, Saturn is one of the most recognizable planets. Smaller and lighter than Jupiter, it has far less gravitational and magnetic influence than its massive neighbor. 3

4 Saturn s Vital Stats Saturn and Auroras Saturn is incredibly light less dense than water! It rotates in less than 11 hrs and also has a very high albedo (mostly due to the cloud layers). This view of Saturn shows high-altitude auroras at both poles on Saturn. You can also see that there are some bands in the atmosphere, but not as much as Jupiter probably due to lower gravity on Saturn. Comparing Jupiter and Saturn Jupiter is 4x more massive, but only 20% bigger than Saturn. This lower mass translates to a lower compression of the hydrogen around Saturn s core and thus produces a weaker magnetic field. Its rocky core is larger but less dense this is mostly because it is not being compressed as much as Jupiter s core. Views of Saturn s Rings The angle of the rings are fixed by Saturn s magnetic field. So, as it revolves, the rings appear to change their shape as seen from the Earth. Every 15 years, the rings appear edge-on and are almost invisible next time is The Rings Have Internal Structure Wow! The rings are not solid, but made up of many smaller rings of various thicknesses and widths. Here you can see some of fthe gaps and rings in the Cassini and Encke divisions of the rings. These gaps are probably caused by small shepherd moons (more later). 4

5 Titan: A Moon with Atmosphere Haze on Titan Titan, the most massive Saturnian moon, is the only moon in the Solar System with an atmosphere. The atmosphere is very hazy and impossible to see through. We do know that it is very cold (200 F below 0) and probably can t support any forms of life. The Hubble ST took this pic in infra-red to look at heat on Titan s surface. Notice that there are features, but we can t tell if they are on the surface or beneath the highest clouds. What are probably seeing is an ocean of liquid ethane and these are warm spots in the moonwide ocean. Shepherd Moons of Saturn This image shows 2 of the 22 known Saturnian moons around one of the outer rings. These moons shepherd the ring particles, using their gravitational influence to keep the ring together and distinct. 5