Chapter 7 The Jovian Planets

7.1 Observations of Jupiter and Saturn Jupiter can be imaged well from Earth, even with a small telescope Here: Jupiter with its Galilean moons

7.1 Observations of Jupiter and Saturn True color image of Jupiter

7.1 Observations of Jupiter and Saturn Natural-color image of Saturn

7.1 Observations of Jupiter and Saturn Cassini image of Jupiter, true color

7.2 The Discoveries of Uranus and Neptune Uranus, in natural color. Note the absence of features.

7.2 The Discoveries of Uranus and Neptune Neptune in natural color

7.3 Bulk Properties of the Jovian Planets The Jovian planets are large and much less dense than the terrestrial planets

7.3 Bulk Properties of the Jovian Planets The Jovian planets are large and much less dense than the terrestrial planets Saturn is less dense than water!

7.3 Bulk Properties of the Jovian Planets The Jovian planets are large and much less dense than the terrestrial planets Saturn is less dense than water! And they spin faster

7.3 Bulk Properties of the Jovian Planets Jovian planets, compared to Earth

7.3 Bulk Properties of the Jovian Planets Peculiarity of Uranus: axis of rotation lies almost in the plane of its orbit. Seasonal variations are extreme.

7.4 Jupiter’s Atmosphere Atmosphere has bright zones and dark belts

7.4 Jupiter’s Atmosphere Atmosphere has bright zones and dark belts Zones are cooler, and are higher than belts

7.4 Jupiter’s Atmosphere Atmosphere has bright zones and dark belts Zones are cooler, and are higher than belts The result of convection

7.4 Jupiter’s Atmosphere Atmosphere has bright zones and dark belts Zones are cooler, and are higher than belts The result of convection Stable flow underlies zones and bands, called zonal flow

7.4 Jupiter’s Atmosphere We know a good deal about the nature of the upper Jupiter atmosphere from a probe dropped from the Galileo orbiter

7.4 Jupiter’s Atmosphere We know a good deal about the nature of the upper Jupiter atmosphere from a probe dropped from the Galileo orbiter The arrow indicates the probe’s entry point.

7.4 Jupiter’s Atmosphere No solid surface; take top of troposphere to be 0 km

7.4 Jupiter’s Atmosphere No solid surface; take top of troposphere to be 0 km Lowest cloud layer cannot be seen by optical telescopes

7.4 Jupiter’s Atmosphere No solid surface; take top of troposphere to be 0 km Lowest cloud layer cannot be seen by optical telescopes Measurements by the Galileo probe show high wind speeds – up to 500 km/h – even at great depth – probably due to heating from planet, not from Sun

7.4 Jupiter’s Atmosphere Major visible features: Bands of clouds; Great Red Spot:

7.4 Jupiter’s Atmosphere Great Red Spot: First observed by Giovanni Cassini or Robert Hooke ~1665

7.4 Jupiter’s Atmosphere Great Red Spot: It is a very long-lived storm, with winds spinning CCW, like a hurricane, sort of…

7.4 Jupiter’s Atmosphere Great Red Spot: It is a very long-lived storm, with winds spinning CCW, like a hurricane, sort of…but what exactly is a hurricane???

The Coriolis Effect

The Coriolis Effect and Storms

The Coriolis Effect and Storms Low pressure storms circulate CCW in northern hemisphere, CW in southern hemisphere

The Coriolis Effect and Storms The Great Red Spot is in the southern hemisphere And the winds go CCW Therefore it is a high-pressure storm

7.4 Jupiter’s Atmosphere Lightning-like flashes have been seen; also shorter-lived rotating storms One example: Brown Oval, really a large gap in clouds Jupiter’s atmosphere is very dynamic

7.5 The Atmospheres of the Outer Jovian Worlds The atmosphere of Saturn is similar to that of Jupiter, except that Saturn is somewhat colder.

7.5 The Atmospheres of the Outer Jovian Worlds Saturn’s atmospheric pressure is also lower Three cloud layers Cloud layers are thicker than Jupiter’s; see only top layer

7.5 The Atmospheres of the Outer Jovian Worlds Jupiter Saturn

7.5 The Atmospheres of the Outer Jovian Worlds Jupiter-style “spots” rare on Saturn; don’t form often and quickly dissipate if they do

7.5 The Atmospheres of the Outer Jovian Worlds Jupiter-style “spots” rare on Saturn; don’t form often and quickly dissipate if they do Winds are even higher than on Jupiter – up to 1500 km/h

7.5 The Atmospheres of the Outer Jovian Worlds Storms near Saturn’s equator:

7.5 The Atmospheres of the Outer Jovian Worlds “Dragon” storm on Saturn – apparently a vast thunderstorm

7.5 The Atmospheres of the Outer Jovian Worlds Rotation of Uranus can be measured by watching storms

7.5 The Atmospheres of the Outer Jovian Worlds Neptune has storm systems similar to those on Jupiter, but fewer. The large storm system at top has disappeared in recent years:

7.6 Jovian Interiors No direct information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is thought to be a rocky core.

7.6 Jovian Interiors Jupiter compared to the other jovian planets

7.6 Jovian Interiors Jupiter compared to the other jovian planets Saturn has a similar structure, but less metallic hydrogen

7.6 Jovian Interiors Jupiter compared to the other jovian planets Saturn has a similar structure, but less metallic hydrogen Uranus and Neptune have no metallic hydrogen

7.6 Jovian Interiors Since Uranus and Neptune have no metallic hydrogen, their magnetic fields are hard to understand

7.6 Jovian Interiors Since Uranus and Neptune have no metallic hydrogen, their magnetic fields are hard to understand They might be due to slushy water solutions of ammonia, which would be electrically conducting

7.6 Jovian Interiors Jupiter’s magnetosphere: Intrinsic field strength is 20,000 times that of Earth Magnetosphere can extend beyond the orbit of Saturn:

7.6 Jovian Interiors Aurorae are seen on Jupiter, and have the same cause as those on Earth – the interaction of solar wind particles with the magnetosphere

7.6 Jovian Interiors Uranus and Neptune both have substantial magnetic fields, but at a large angle to their rotation axes. The rectangle within each planet shows a bar magnet that would produce a similar field. Note that both Uranus’s and Neptune’s are significantly off center.

Summary of Chapter 7 Jupiter and Saturn were known to the ancients; Uranus was discovered by chance, and Neptune was predicted from anomalies in the orbit of Uranus Jovian planets are large but not dense; they are fluid and display differential rotation Cloud layers have light zones and dark bands; wind pattern, called zonal flow, is stable

Summary of Chapter 7 Storms appear with regularity; the Great Red Spot of Jupiter has lasted for hundreds of years (that we know of) Due to conductive interiors and rapid rotation, Jovian planets have large magnetic fields Jupiter, Saturn, and Neptune radiate more energy than they receive from the Sun