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