Chapter 11 Jupiter Chapter 11 opener. Jupiter is certainly one of the most fascinating objects in the solar system. This is a true color mosaic, constructed from two dozen images taken by a camera onboard the Cassini spacecraft during its closest approach in 2001. It is the most detailed portrait of Jupiter ever produced, resolving features to as small as 60 kilometers. Note the Great Red Spot – a storm that has been under way for several hundred years. Everything seen here is a cloud, from the equatorial regions that show alternating light and dark belts, to high-latitude areas that appear more mottled. All these varying structures display differing cloud heights, thickness, and chemical compositions. (JPL)

Units of Chapter 11 11.1 Orbital and Physical Properties 11.2 The Atmosphere of Jupiter A Cometary Impact 11.3 Internal Structure Almost a Star? 11.4 Jupiter’s Magnetosphere 11.5 The Moons of Jupiter 11.6 Jupiter’s Ring

11.1 Orbital and Physical Properties This figure shows the solar system from a vantage point that emphasizes the relationship of the jovian planets to the rest of the system Figure 11-1. Solar System Perspective This is a variation on Figure 6.5—neither an overhead view or an edge-on view of our solar system, but an oblique view from a distant perspective—illustrating the jovian planets relative to their terrestrial cousins. Jupiter orbits at a distance of 5.2 AU from the Sun, outside the asteroid belt but well inside the Kuiper belt.

Three views of Jupiter: From a small telescope on Earth; from the Hubble Space Telescope; and from the Cassini spacecraft Figure 11-2. Jupiter (a) Photograph of Jupiter made through a ground-based telescope, showing the planet and several of its Galilean moons. (b) A Hubble Space Telescope image of Jupiter, in true color. Features as small as a few hundred kilometers across are resolved. (c) A Cassini spacecraft image of Jupiter, taken while the vehicle was on its way to Saturn, shows intricate clouds of different heights, thicknesses, and chemical composition. (NASA; AURA)

Radius: 71,500 km (11.2 times Earth’s) Mass: 1.9 × 1027 kg (twice as much as all other planets put together) Radius: 71,500 km (11.2 times Earth’s) Density: 1300 kg/m3—cannot be rocky or metallic as inner planets are Rotation rate: Problematic, as Jupiter has no solid surface; different parts of atmosphere rotate at different rates From magnetic field, rotation period is 9 hr, 55 min

11.2 The Atmosphere of Jupiter Major visible features: Bands of clouds; Great Red Spot Figure 11-4. Jupiter’s Red Spot Voyager 1 took this photograph of Jupiter’s Great Red Spot (upper right) from a distance of about 100,000 km. Resolution is about 100 km. Note the complex turbulence to the left of both the Red Spot and the smaller white oval below it. (For scale, planet Earth has been superposed.) (NASA)

Atmosphere has bright zones and dark belts Zones are cooler, and are higher than belts Stable flow, called zonal flow, underlies zones and bands Simplified model Figure 11-5. Jupiter’s Convection The colored bands in Jupiter’s atmosphere are associated with vertical convective motion. Upwelling warm gas results in zones of lighter color; the darker bands overlie regions of lower pressure where cooler gas sinks back down into the atmosphere. As on Earth, surface winds tend to blow from high- to low-pressure regions. Jupiter’s rapid rotation channels those winds into an east–west flow pattern, as indicated by the three yellow-red arrows drawn atop the belts and zones. The inset is a Voyager photo of part of Jupiter’s cloud layer, as seen from above, showing the planet’s actual banded structure. (NASA)

Real picture is much more complicated Here: Wind speed with respect to internal rotation rate Figure 11-6. Zonal Flow The wind speed in Jupiter’s atmosphere, measured relative to the planet’s internal rotation rate. Alternations in wind direction are associated with the atmospheric band structure.

Composition of atmosphere: mostly molecular hydrogen and helium; small amounts of methane, ammonia, and water vapor These cannot account for color; probably due to complex chemical interactions

No solid surface; take top of troposphere to be at 0 km Lowest cloud layer cannot be seen by optical telescopes Measurements by Galileo probe show high wind speeds even at great depth—probably due to heating from planet, not from Sun Figure 11-7. Jupiter’s Atmosphere Models of the vertical structure of Jupiter’s atmosphere suggest that the planet’s clouds are arranged in three main layers, each with quite different colors and chemistry. The colors we see in photographs of the planet depend on the cloud cover. The white regions are the tops of the upper ammonia clouds. The yellows, reds, and browns are associated with the second cloud layer, which is composed of ammonium hydrosulfide ice. The lowest (bluish) cloud layer is water ice; however, the overlying layers are sufficiently thick that this level is not seen in visible light. The blue curve shows how Jupiter’s atmospheric temperature depends on altitude. (For comparison with Earth, see Figure 7.2.)

Color and energy source still not understood Great Red Spot has existed for at least 300 years, possibly much longer Color and energy source still not understood Figure 11-9. Red Spot Details These Voyager 2 close-up views of the Great Red Spot, taken 4 hours apart, show clearly the turbulent flow around its edges. The general direction of motion of the gas north of (above) the spot is westward (to the left), whereas gas south of the spot flows east. The spot itself rotates counterclockwise, suggesting that it is being “rolled” between the two oppositely directed flows. The colors have been exaggerated somewhat to enhance the contrast. (NASA)

One example: Brown Oval, really a large gap in clouds Lightning-like flashes have been seen; also shorter-lived rotating storms One example: Brown Oval, really a large gap in clouds Figure 11-10. Brown Oval This brown oval in Jupiter’s northern hemisphere is actually a break in the upper cloud layer, allowing us to see deeper into the atmosphere, where the clouds are brown. The oval’s length is approximately equal to Earth’s diameter. (NASA)

Recently, three white storms were observed to merge into a single storm, which then turned red. This may provide some clues to the dynamics behind Jupiter’s cloud movements. Figure 11-11. Red Spot Junior (a) Between 1997 and 2000, astronomers watched as three white ovals in Jupiter’s southern hemisphere merged to form a single large storm. Each oval, captured here by the Cassini spacecraft cameras, is about half the size of Earth. (b) In early 2006 the white oval turned red, producing a second red spot! The color change may indicate that the storm is intensifying. (c) In mid-2008, the Hubble telescope recorded this sequence of images at monthly intervals (left to right), showing a “baby red spot” (arrows) approaching the Great Red Spot and being destroyed by it.(NASA)

Discovery 11-1: A Cometary Impact July 1994: Comet Shoemaker-Levy 9, in fragments, struck Jupiter, providing valuable information about cometary impacts

11.3 Internal Structure Find that Jupiter radiates more energy than it receives from the Sun: Core is still cooling off from heating during gravitational compression Could Jupiter have been a star? No; it is far too cool and too small for that. It would need to be about 80 times more massive to be even a very faint star.

No direct information is available about Jupiter’s interior, but its main components, hydrogen and helium, are quite well understood. The central portion is a rocky core. Figure 11-12. Jupiter’s Interior Jupiter’s internal structure, as deduced from Voyager measurements and theoretical modeling. The outer radius represents the top of the cloud layers, some 70,000 km from the planet’s center. The density and temperature increase with depth, and the atmosphere gradually liquefies at a depth of a few thousand kilometers. Below a depth of 20,000 km, the hydrogen behaves like a liquid metal. At the center of the planet lies a large rocky core, somewhat terrestrial in composition, but much larger than any of the inner planets. Although the values are uncertain, the temperature and pressure at the center are probably about 25,000 K and 60 million (Earth) atmospheres, respectively.

11.4 Jupiter’s Magnetosphere Jupiter is surrounded by belts of charged particles, much like the Van Allen belts but vastly larger Magnetosphere is 30 million km across Figure 11-15. Jupiter’s Magnetosphere Jupiter’s inner magnetosphere is characterized by a flat current sheet consisting of charged particles squeezed into the magnetic equatorial plane by the planet’s rapid rotation. The plasma torus, a ring of charged particles associated with the moon Io, is discussed in Section 11.5.

Intrinsic field strength is 20,000 times that of Earth Magnetosphere can extend beyond the orbit of Saturn Figure 11-13. Pioneer 10 Mission The Pioneer 10 spacecraft (a forerunner of the Voyager missions) did not detect any solar particles while moving far behind Jupiter in 1976. Accordingly, as sketched here, Jupiter’s magnetosphere apparently extends beyond the orbit of Saturn.

11.5 The Moons of Jupiter 63 moons have now been found orbiting Jupiter, but most are very small The four largest are the Galilean moons, so called because they were first observed by Galileo: Io, Europa, Ganymede, Callisto Galilean moons have similarities to terrestrial planets: orbits have low eccentricity, largest is somewhat larger than Mercury, and density decreases as distance from Jupiter increases

Jupiter with Io and Europa. Note the relative sizes! Figure 11-17. Jupiter, Up Close Voyager 1 took this photo of Jupiter with ruddy Io on the left and pearllike Europa toward the right. Note the scale of objects here: Both Io and Europa are comparable in size to our Moon, and the Red Spot is roughly twice as big as Earth. (NASA)

Interiors of the Galilean moons Figure 11-18. Galilean Moon Interiors Cutaway diagrams showing the interior structure of the four Galilean satellites. Moving outward from Io to Callisto, we see that the moons’ densities steadily decrease as the composition shifts from rocky mantles and metallic cores in Io and Europa, to a thick icy crust and smaller core in Ganymede, to an almost uniform rock and ice mix in Callisto. Both Ganymede and Europa are thought to have layers of liquid water beneath their icy surfaces.

Io is the densest of Jupiter’s moons, and the most geologically active object in the solar system: Many active volcanoes, some quite large Can change surface features in a few weeks No craters; they fill in too fast—Io has the youngest surface of any solar system object

Orange color is probably from sulfur compounds in the ejecta Figure 11-19. Io Jupiter’s innermost moon, Io, is quite different in character from the other three Galilean satellites. Its surface is kept smooth and brightly colored by the moon’s constant volcanism. The resolution of the Galileo photograph in (a) is about 7 km. In the more detailed Voyager image (b), features as small as 2 km across can be seen. (NASA)

Cause of volcanism: Gravity! Io is very close to Jupiter and also experiences gravitational forces from Europa. The tidal forces are huge and provide the energy for the volcanoes. Figure 11-20. Volcanoes on Io The main image shows a Galileo view of Io with a resolution of about 6 km. The dark, circular features are volcanoes. The left inset shows an umbrella-like eruption of one of Io’s volcanoes, captured as Galileo flew past this fascinating moon in 1997; the plume measures about 150 km high and 300 km across. The right inset shows another volcano, this one face-on, where surface features here are resolved to just a few kilometers. (NASA)

Volcanic eruptions also eject charged particles; these interact with Jupiter’s magnetosphere and form a plasma torus Figure 11-21. Io Plasma Torus The torus is the result of material being ejected from Io’s volcanoes and swept up by Jupiter’s rapidly rotating magnetic field. Spectroscopic analysis indicates that the torus is made mainly of sodium and sulfur atoms and ions.

Europa has no craters; surface is water ice, possibly with liquid water below Tidal forces stress and crack ice; water flows, keeping surface relatively flat Figure 11-22. Europa (a) Voyager 1 mosaic of Europa. Resolution is about 5 km. (b) Europa’s icy surface is only lightly cratered, indicating that some ongoing process must be obliterating impact craters soon after they form. The origin of the cracks crisscrossing the surface is uncertain. (c) At 5-m resolution, this image from the Galileo spacecraft shows a smooth yet tangled surface resembling the huge ice floes that cover Earth’s polar regions. This region is called Conamara Chaos. (d) This detailed Galileo image shows “pulled apart” terrain that suggests liquid water upwelling from the interior and freezing, filling in the gaps between separating surface ice sheets. (NASA)

History similar to Earth’s Moon, but water ice instead of lunar rock Ganymede is the largest moon in the solar system—larger than Pluto and Mercury History similar to Earth’s Moon, but water ice instead of lunar rock Figure 11-23. Ganymede (a) and (b) Voyager 2 images of Ganymede. The dark regions are the oldest parts of the moon’s surface and probably represent its original icy crust. The largest dark region visible here, called Galileo Regio, spans some 3200 km. The lighter, younger regions are the result of flooding and freezing that occurred within a billion years or so of Ganymede’s formation. The light-colored spots are recent impact craters. (c) Grooved terrain on Ganymede may have been caused by a process similar to plate tectonics on Earth. The area shown in this Galileo image spans about 50 km and reveals a multitude of ever-smaller ridges, valleys, and craters, right down to the resolution limit of the spacecraft’s camera (about 300 m, three times the length of a football field). The image suggests erosion of some sort, possibly even caused by water. (NASA)

Callisto is similar to Ganymede; no evidence of plate activity Figure 11-24. Callisto (a) Callisto, the outermost Galilean moon of Jupiter, is similar to Ganymede in overall composition, but is more heavily cratered. The large series of concentric ridges visible at left is known as Valhalla. Extending nearly 1500 km from the basin center, the ridges formed when “ripples” from a large meteoritic impact froze before they could disperse completely. Resolution in this Voyager 2 image is about 10 km. (b) This higher-resolution Galileo image of Callisto’s equatorial region, about 300 × 200 km in area, displays more clearly its heavy cratering. (NASA)

11.6 Jupiter’s Ring Jupiter has been found to have a small, thin ring Figure 11-25. Jupiter’s Ring Jupiter’s faint ring, as photographed (nearly edge-on) by Voyager 2. Made of dark fragments of rock and dust possibly chipped off the innermost moons by meteorites, the ring was unknown before the two Voyager spacecraft arrived at the planet. It lies in Jupiter’s equatorial plane, only 50,000 km above the cloud tops. (NASA)

The chemical composition of Jupiter indicates the two most abundant elements are: A. silicon and carbon. B. silicon and oxygen. C. hydrogen and helium. D. hydrogen and oxygen.

Jupiter's moon Io has no observable impact craters because: A. volcanic activity has covered them over. B. its proximity to Jupiter prevents large impacts. C. the surface is molten and meteorites sink into it. D. a thick atmosphere keeps us from seeing the surface.

Consider the fact that both Jupiter and the earth have strong planetary magnetic fields. In the context of the dynamo model, this means that both planets have: A. rapid rotation and conducting cores. B. conducting cores of metals like iron and nickel. C. dense cores of lead and uranium. D. rapid rotation and fusion of hydrogen into helium.

The great red spot of Jupiter is thought to be caused by an enormous volcano. a region of hotter gases. a long-lasting cyclonic storm. an opening through the high level clouds revealing a portion of the atmosphere nearer the surface.

Which of the following are true about Jupiter's belts (dark) and zones (light) belts are rising while zones are sinking. belts are sinking while zones are rising. both belts and zones are rising. both belts and zones are sinking .

The chemical composition of Jupiter is most similar to Earth the sun Mars Venus

The source of Jupiter's excess energy is thought to be lightning bolts in the atmosphere. internal heat left over from its formation. produced by tides between the planet and the sun. energy absorbed from beyond the solar system and then re-emitted.

Summary of Chapter 11 Jupiter is the largest planet in the solar system Rotates rapidly Cloud cover has three main layers, forms zone and band pattern Great Red Spot is a very stable storm Pressure and density of atmosphere increase with depth; atmosphere becomes liquid and then “metallic”

Summary of Chapter 11 (cont.) Relatively small rocky core (but still about 10x size of Earth) Still radiating energy from original formation 63 moons, four very large Io: active volcanoes, due to tidal forces Europa: cracked, icy surface; may be liquid water underneath Ganymede and Callisto: similar; rock and ice