Post on 19-Jan-2018
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Chapter 7The Jovian Planets
Jupiter from Spacecraft Cassini
Figure 7.1Jupiter a) earth based telescope, b) HST
Figure 7.2Saturn from HST
Spacecraft Jovian Exploration
• Gravity assist
• Voyager 1 & 2• Galileo• Cassini-Huygens
More Precisely 7-1Gravitational “Slingshots”
Voyager 1 & 2 spacecraft• Launched 1977• Reached Jupiter 1979• Used gravity assist• 1 reached Saturn 1980• 2 reached Saturn 1981• 2 reached Uranus 1986• 2 reached Neptune 1989
More Precisely 7-1Gravitational “Slingshots”
Galileo spacecraft• Launched 1989• Three gravity assists through inner solar
system• Reached Jupiter December 1995• Probe entered Jupiter’s atmosphere• Orbiter studied Jupiter’s moons
Figure 7.10Galileo’s Atmospheric Probe Entry Site
Figure 7.3Jupiter from Cassini (on way to Saturn)
Cassini-Huygens spacecraft• Launched October 1997• Reached Saturn July 2004• Cassini - orbiter and Huygens - probe• Huygens entered Titan’s atmosphere
January 2005
Figure 7.4Uranus from Voyager 2
Uranus• Discovered by William Herschel in 1781• Barely visible to naked eye• Orbit not exactly elliptical• Another planet influencing it
Figure 7.5Neptune from Voyager 2
Discovery of Neptune• Orbit predicted by• Englishman John Adams 1845 and• Frenchman Urbain Leverrier 1846• First seen by German Johann Galle
1846
Figure 7.6Jovian Planets - Relative size
Table 7.1Planetary Properties
Rotation rates
• Not solid - differential rotation• Atmosphere at various latitudes rotate
different rates• Magnetosphere rotates
Jovian Planet Physical Properties
• Strong gravity held original atmosphere - mainly H and He
• Each has dense compact core• Atmospheres liquid in interior
Analogy 7.1Saturn would float
Axial tilt
• (Earth 23.5°)• Jupiter 3°• Saturn 27°• Uranus 98° (axis roughly parallel to
ecliptic)• Neptune 30°
Figure 7.7Seasons on Uranus
Jupiter’s atmosphere
• Molecular Hydrogen 86%• Helium 14%• Small amounts of methane, ammonia,
H2O
Figure 7.8Jupiter’s Convection
Cloud bands
• Lighter zones - warm material rising, high pressure
• Darker belts - cool material sinking, low pressure
Figure 7.9Jupiter’s Atmosphere
Atmospheric layers
• Haze on top 110 K• White ammonia clouds 125 - 150 K• Ammonium hydrosulfide ice 200 K• H2O ice• Gaseous H, He, methane, ammonia,
H2O
Weather on Jupiter
• Great Red Spot• White spots• Brown oval
Figure 7.11Jupiter’s Red Spot and a white spot
Great Red Spot
• 2X size of earth• Large hurricane like storm• More than 300 years old• Earth hurricanes die out over land
Figure 7.12Jupiter’s Brown Oval
Figure 7.13Saturn
a) Voyager 2, b) Cassini
Saturn’s atmosphere
• Molecular H 92.4%• Helium 7.4% - less than Jupiter -
liquefied and sank• Traces of methane and ammonia• Less gravity, so thicker than Jupiter’s
atmosphere• Not as colorful (fewer holes/gaps)
Figure 7.14Saturn’s Atmosphere
Figure 7.15Saturn Storm from HST a) 2 hour intervals b) infrared
Figure 7.16Saturn’s “Dragon Storm”
Uranus and Neptune atmospheres
• Molecular H 84%• Helium 14%• Methane - Neptune 3%, Uranus 2%• Methane absorbs long wavelengths
(red)• Neptune more blue than Uranus
Figure 7.17Uranus’s Rotation
a), b), c) 4 hour intervald) rings and clouds, infrared
Figure 7.18a) Neptune’s Dark Spot (Voyager 2) b) later disappeared
Jupiter’s interior
• Top layers are gas - molecular H• At several thousand km, liquid• Liquid metallic H• Rocky core
Figure 7.19Jupiter’s Interior
Saturn’s interior
• Top layers are gas - molecular H• Thinner metallic H layer• Larger rocky core
Figure 17.20Jovian Interiors
Jovian magnetospheres
• Stronger than Earth’s
• Caused by fast rotation
• Jupiter - largest and strongest magnetosphere
• Aurora on Jupiter
Figure 7.21Pioneer 10 Mission
Figure 7.22Aurorae on Jupiter
Figure 7.23Jovian Magnetic Fields
Jovian internal heating
• Jupiter - emits 2X more energy than absorbed (left over heat)
• Saturn - 3X (helium rain and gravitational compression)
• Neptune - 2.7X
Discovery 7-1A Cometary Impact