Jupiter Orbit, Rotation Physical Properties Atmosphere, surface Interior Magnetosphere Moons (Voyager 1) Jupiter is the third-brightest object in the night sky (after the Moon and Venus). Exploration by Spacecrafts Pioneer & Voyager (1970s) Pioneer 10 (March 1972) Pioneer 11 (April 1973) Voyager 1 & 2 (1977) Galileo (Launched in 1989 and arrived at Jupiter in 1995) Future plan Europa Orbiter mission (2008) 1
Jupiter s Orbital Motion Perihelion Average distance from Sun ~ 5.2 A.U. 4.95 A.U. Orbital eccentricity 0.048 Conjunction Sun Earth Opposition (largest & brightest) 5.46 A.U. Aphelion Physical Properties Equatorial radius: ~ 71,492 km (11.2 times that of Earth) Mass: 1.9 x 10 27 Kg (318 times that of the Earth) (More than 1400 Earths would be needed to equal the volume of Jupiter.) Average density: 1330 kg/m 3 (0.24 times that of the Earth) Surface gravity (at cloud tops): 24.8 m/s 2 (2.5 times that of Earth) Magnetic field: ~ 14 times that of Earth Surface temperature: 124 K (at cloud tops) (273 K is freezing, 373 K is boiling, 0 K is absolute zero) Moons: 16 (named), 28 (total at last count) (only 4 large moons) Axial tilt: 3.08 (almost perpendicular to the ecliptic) Sidereal orbit: 11.9 Earth years Synodic period: 1.1 Earth years (time between oppositions) Rotation period: 9 hrs 50 min at equator, 9 hr 55 min at poles (not a solid body!) 2
Rotational Flattening Jupiter exhibits differential rotation the rotation rate is not constant from one location to another. Jupiter has the fastest rotation rate of any planet in the solar system, and this rapid spin has altered Jupiter s shape. 66,900 km 71,492 km Jupiter s Features Zone Belt Great Red Spot (Earth-sized hurricane) White oval 3
Convection in the Atmosphere The zones and belts vary in both latitude and intensity during the year due to the dynamic motion in the planet s atmosphere. Belts -- low pressure Zones -- high pressure - convection caused by internal heat. - Jupiter emits twice the radiation it receives from Sun. Zonal Flow The equatorial regions of the atmosphere rotate faster than the planet, with an average flow speed of about 300 km/h, in the easterly direction. 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. 4
Atmosphere Composition: Hydrogen 86.1 % Helium 13.8 % Together these two gases make up over 99 % of Jupiter s atmosphere. Traces: methane, ammonia, and water vapor Zone Belt Colors from compounds containing sulfur, phosphorus Jupiter s Great Red Spot Westward Counterclock wise (~ 6 days) Eastward Age: at least 40 years The size of the Spot varies, although it averages about twice the diameter of Earth. At present ~ 25,000 km x 15,000 km. What is the origin of the Spot s red color and its source of energy?? Unknown!! 5
Interior Jupiter emits twice the radiation it receives from Sun. From where this extra energy is coming? Jupiter must have its own internal heat source. Liquid metal The source of Jupiter s excess energy is the slow escape of gravitational energy released during the planet s formation. Core (rocky in nature) silicate/metals, 10 times mass of Earth Magnetosphere Jupiter s magnetosphere is ~ 30 million km across, (roughly a million times more voluminous than Earth s magnetosphere). The intrinsic strength of the planet s magnetic field is nearly 20,000 times greater than Earth s. 10 0 3 million Km Beyond the Saturn s orbit 6
Aurora on Jupiter Aurorae 7
The Moons of Jupiter Total Moons at last count : 28, (16 named) Galilean Moons: Moving outward from Jupiter, the four moons named Io, Europa, Ganymede, and Callisto, comparable in size to Earth s Moon are called Galilean Moons after the name of their discoverer Galileo. Within the orbit of Io lie four small satellites. The largest of the four, Amalthea, is less than 300 km across and is irregularly shaped, orbits synchronously at a distance of 181,000 km from Jupiter s center. Beyond the Galilean moons lie eight more small satellites that fall into two groups. The inner group move in eccentric, inclined orbits, about 11 million km from the planet. The outer four moons lie about 22 million km from Jupiter. Their orbits too are fairly eccentric, but retrograde. The latest addition --- 12 small moons (5 or 10 km across, 10 to 25 million km away, retrograde, 10-30 inclined). Galilean Moons These four move in nearly circular orbits about their parent planet. Their orbits are direct (prograde). They all lie close to Jupiter s equatorial plane. They range in size from slightly smaller than Earth s Moon (Europa) to slightly larger than Mercury (Ganymede). They generally have rocky mantle. Galilean moons have several interesting parallels with the terrestrial planets. 8
Galilean Moons Internal Structure Density: 3500 kg/m 3 3000 kg/m 3 Ratio of ice/rock increases No. of Craters increases 2000 kg/m 3 2000 kg/m 3 Io (The Most Active Moon) Smooth and bright colored surface (youngest surface) Lava Flow (Liquid Sulfur) 9
Voyager discovered active volcanoes on Io! Volcano is ejecting matter to an altitude of over 100 km with the speed of 2km/s. Lava temperatures generally range from 650 to 900 K but can be as high as 2000 k. Io (Eruption Near Pele Volcano) 300 km 10
Io plasma torus A doughnut-shaped region of energetic heavy ions that follows Io s orbital track, completely encircling Jupiter. Io Io orbits very close to Jupiter only 422,000 km, or 5.9 Jupiter radii. Active volcanoes with plumes extending up to 300 km and ejected gases traveling up to 2 km/sec. Ejected gas contains sulfur dioxide (SO 2 ) - much of this escapes to form the Io Torus. Lava contains high concentration of Sulfur compounds red/orange/yellow colors. Lava temperatures up to 2000 K. Surface is very smooth no impact craters. - Surface is youngest: < 1 million years Interior is molten and produce astounding volcanic activity due to tidal forces from Jupiter and tugs from Europa. 11
Europa Rocky deposits Relatively few craters -geologically youth just a few million years. Europa (Ice Rafting) 250 km A vast network of lines crisscrossing bright, clear fields of water ice. Resemble the pressure ridges that develop in ice floes on Earth s polar oceans. 12
Europa Lying outside Io s orbit, at 671,000 km (9.4 Jupiter radii). Surface is covered with ice (100 km deep liquid ocean below it). Only a few craters surface is young. Probably liquid water underneath! Fractures in the surface due to ice motions have released water mixed with darker material. The constant change in strength and direction of Europa s weak magnetic field is also a indication of embedded ocean below the surface. Surface was warmer in the past oceans present? Suitable conditions for life? Next NASA mission: Europa orbiter (2003) Ganymede Galileo Regio (320 km across) Original icy surface (oldest part) The largest moon in the solar system. Its surface has: impact craters. patterns of dark and light markings (the highlands and maria). light-colored parts are maria and as they are much less heavily cratered, so they must be younger. 13
Ganymede (Young Craters on Grooved and ridged Terrain) Gula - 38 km Achelous - 32 km Grooves and ridges on Ganymede surfaced resulted from crustal tectonic motion that took place about 3 billion years ago. Callisto It is similar to Ganymede in composition but is more heavily cratered. The large series of concentric ridges is known as Valhalla. Extending nearly 1500 km from the basin center, they formed when "ripples" from a large meteoritic impact refroze before they could disperse completely. 14
Ganymede/ Callisto Ganymede orbits at 1.1 million km, or 15 planetary radii, and Callisto at 1.9 million km, or 26 Jupiter radii from the center of Jupiter. Both larger than Earth s Moon. - Ganymede is larger than Mercury and Pluto. Heavily cratered no recent geologic activity. Low density roughly equal amounts of ice and rock. Callisto is not differentiated mixture of ice and rock throughout. Jupiter s Ring This ring lies roughly 50,000 km above the top cloud layer of the Jupiter, inside the orbit of the innermost moon. 15