Transcript Jupiter

12a. Jupiter
• Jupiter
data
• Jupiter seen from the Earth
• Jupiter rotation & structure
• Jupiter
clouds
• Jupiter atmospheric motions
• Jupiter
rocky core
• Jupiter
magnetic field
Jupiter Data (Table 12-1)
Jupiter Data: Numbers
• Diameter: 142,800.km
11.19 ⋅ Earth
• Mass:
1.9 ⋅ 1027 kg
• Density:
1.3 ⋅ water
0.24 ⋅ Earth
• Orbit:
7.8 ⋅ 108 km
5.20 AU
• Day:
9h.50m 30s
0.41 ⋅ Earth
• Year:
11.86 years
11.86 ⋅ Earth
317.8 ⋅ Earth
Jupiter Data: Special Features
• Jupiter is the closest Jovian planet to the Sun
• Jupiter is the largest Jovian planet
– Jupiter is ~2.5 . mass of all other planets combined
• Jupiter has no solid surface
• Jupiter has a colorful & dynamic atmosphere
– Great Red Spot, belts & zones…
• Jupiter’s interior consists of three layers…
– Atmosphere: Liquid molecular hydrogen
– Mantle:
Liquid metallic hydrogen
– Core:
“Metal” & “rock”
• Jupiter has 4 large & 63 small known moons
– Io is the most volcanically active body known
Jupiter As Seen From Earth
• The first telescopic observer of Jupiter
– Galileo Galilei
1609
• Immediately noticed the four largest moons of Jupiter
• Recognized the similarity between them and the planets
• More recent telescopic observers
– Robert Hooke
1664
• Noticed the Great Red Spot in the southern hemisphere
• It has persisted in some form until now
– Cassini
1690
• Cloud bands drawn out by Jupiter’s very fast axial rotation
• Used these to measure 9h 50m 28s equatorial Jovian day
• Discovered Jupiter’s differential axial rotation
Rotation
– Jupiter rotates fastest at its equator than at its poles
Jupiter is Made of Low-Mass Gases
• Jupiter is mostly hydrogen & helium
– The numbers
• By mass
~ 71% H2
~ 24% He
~ 5% others
• By atoms
~ 91% H2
~ 8% He
~ 1% others
– The evidence
• Detected spectra of CH4 (methane) & NH3 (ammonia)
• Cold H2 & He are extremely difficult to detect
– UV spectra detected in 1960
• Jupiter does have a rocky & metallic core
– May have been the “seed” for the rest of Jupiter
Cloud Details in Spacecraft Images
• Pioneer 10 & Pioneer 11 fly-bys
1973 & 1974
– First close-up images of Jupiter
– Spectacular images of Galilean moons, esp. Io
• Voyager 1 & Voyager 2 fly-bys
1979
– Spectacular close-ups of Jovian storm systems
– Additional details of most Jovian moons
• Galileo atmospheric probe & orbiter
1995
– Probe entered clear area in Jupiter’s clouds
– Severely crippled yet operated until 21 Sep. 2003
• Cassini
2000
– The primary mission is to Saturn
– Imaged Jupiter during gravity-assist [slingshot] fly-by
• Simultaneous observations by Galileo
Patterns In Jupiter’s Clouds
Jupiter Seen From Far & Near
Earth-based telescope
Voyager 1 spacecraft
Five Historic Views of Jupiter
Jupiter’s Great Red Spot
• Solar System champ
– Longest lasting storm system
– Largest
storm system
Since 1664
~ 25,000 mi
• Basic characteristics
– Imbedded in Jupiter’s southern hemisphere
– Much higher than surrounding clouds
– Circulates counterclockwise
• Characteristic of a high pressure system
• Similar to high pressure systems in Earth’s atmosphere
– Size varies considerably
• From ~ 1 to ~3 times Earth’s diameter
– Color varies considerably
• From deep red to light pink
Voyager 2: The Great Red Spot
Jupiter & Ganymede: Family Portrait
Three Factors Affect Cloud Motions
• Insolation
Incoming solar radiation
– Jupiter’s orbit is ~ 5.2 AU from the Sun
• ~ 3.7% as much energy per m2 as Earth
– Jupiter’s albedo is 0.44 compared to Earth’s 0.39
• Effectively reduces solar energy to ~ 3.3% of Earth
– Sunlight is absorbed by Jupiter’s atmosphere
• Jupiter’s internal heat
– Jupiter emits ~ 2x as much energy as from sunlight
• Old heat from Jupiter’s formation
• New heat from helium condensation
• Differential axial rotation
– Multiple convection cells in Jupiter’s atmosphere
– Drawn out into bands parallel to Jupiter’s equator
• Adjacent bands move in opposite directions Zonal winds
Spectroscopy of Jupiter’s Atmosphere
• Three primary cloud layers
– Upper layer
• Ammonia (NH3) ice crystals
– Middle layer
~ 20 km below Tmin
~ 40 km below Tmin
• Ammonium hydrosulfide (NH4SH) ice crystals
– Lower layer
• Water (H2O) ice crystals
~ 60 km below Tmin
• Major cloud features
– Belts
&
zones
• Belts are bands of falling air
• Zones are bands of rising air
Relatively low & warm
Relatively high & cool
– Brown & white ovals
• White ovals lie relatively high in Jupiter’s atmosphere
– Smaller versions of the Great Red Spot
• Brown ovals lie relatively low in Jupiter’s atmosphere
Jupiter’s Upper Atmosphere Structure
Jupiter’s (Low) Belts & (High) Zones
Jupiter’s Distinctive Cloud Colors
• Mostly “Earth tones”
– Yellow, brown, pink, red…
– Colors vary over time & space
• Source of colors
– All three cloud layer chemicals are white if pure
• Spectroscopy reveals no substantial impurities
– Jupiter’s moon Io is extremely active volcanically
• Io has abundant sulfur compounds
• Io has the same colors as Jupiter’s clouds
• Io spews matter into space near Jupiter
• Jupiter’s cloud colors may come from Io’s eruptions
Jupiter’s Deep Atmosphere: S-L 9
• Comet Shoemaker-Levy 9
16-22 July 1994
– 23 visible fragments entered Jupiter’s atmosphere
• All less than ~ 1 km in diameter
• Entry speed of ~ 60 km ⋅ sec–1
~ 130,000 mph
– Satellites orbit Earth at ~ 8 km ⋅ sec–1
• Largest fragment energy equivalent of 6 ⋅ 108 megatons
– 10,000°C fireballs rose 3,000 km above the clouds
• Hopes for eruptions of deep atmospheric layers
• Confounded by uncertainties about comet’s composition
S-L9: The String of Pearls Comet
Comet Shoemaker-Levy 9 Hits Jupiter
Jupiter’s Deep Atmosphere: Galileo
• Galileo atmospheric probe
7 December 1995
• Only spacecraft to enter Jupiter’s atmosphere
– Entry speed of ~ 49 km . sec–1
~ 106,000 mph
– Decelerated to ~ 40 km . hr–1 in 3 min.
~ 25 mph
– Descended by parachute for ~ 1 hour
– Reached ~ – 200 km & + 24 x Earth’s air pressure
Jupiter’s Atmosphere Findings
• Relatively rare but extremely powerful lightning
• Nearly constant winds of ~ 650 km ⋅ hr–1
– Much faster than solar-driven high altitude winds
– This wind energy must come from Jupiter’s interior
• Cloud layer measurements
– Galileo Probe’s bad luck ⇒ Entered a clear spot
– Traces of NH3 & NH4SH clouds but no H2O clouds
• Atmospheric gases
– Virtually identical to the Sun
– Only ½ expected amount of atmospheric H2O vapor
The Galileo Probe Timeline
Probe video
Oblate Shape Means a Rocky Core
• Distinctly larger equatorial than polar diameter
– ~ 6.5 % difference for Jupiter
– ~ 0.34% difference for Earth
• Axial rotation spins equatorial material away
– Centrifugal effect
• Planetary core mass modifies centrifugal effect
– Metallic & rocky inner core
• Estimated to be ~ 2.6% of Jupiter’s mass
• Only ~ 8 x Earth’s mass yet ~ 86% Earth’s diameter
– Liquid “ices” outer core
• Primarily water (H2O), methane (CH4) & ammonia (NH3)
• Estimated to be ~ 3,000 km thick
Jupiter’s Four-Layer Internal Structure
Jupiter's Interior
Metallic Hydrogen & Magnetosphere
• Radio observations of Jupiter
1950’s
– Evidence of electric currents
– Different types of radio emissions
• Thermal emissions
Blackbody radiation
• Non-thermal emissions
– Wavelengths of a few meters
Decametric radiation
– Wavelengths of a few tenths of a meter
Decimetric radiation
• Jupiter’s magnetic field is ~ 14 x Earth’s magnetic field
• Possible causes
– H2 is a liquid metal above 1.4 . 106 atmospheres
• Pressure is reached ~ 7,000 km below Jupiter’s clouds
• The “gas giant” Jupiter is mostly liquid metallic hydrogen
Jupiter’s Immense Magnetosphere
• Spacecraft measurements
– Pioneer & Voyager
• Magnetosphere is ~ 3.0 . 107 km in diameter
– ~ 210 times Jupiter’s
diameter as seen from Earth
– ~ 2.5 times the Moon’s diameter as seen from Earth
– ~ 6.3 times the Moon’s
area as seen from Earth
• Magnetosphere extends beyond the orbit of Saturn
– Jupiter’s magnetotail is ~ 6 AU long
• Emissions variations repeat every 9h 55m 28s
– Assumed to be the core axial rotation rate of Jupiter
– Galileo
• Suffered extensive radiation damage orbiting Jupiter
• Basic characteristics
– Jupiter’s magnetosphere is filled with plasma
– Solar wind gusts alter Jupiter’s magnetosphere
• Magnetosphere’s size varies by a factor of 2
Jupiter’s Magnetosphere
A schematic
view
A radio view
Juno: Jupiter’s Newest Spacecraft
• Basic details
– Launched 5 August 2011
– Six-year planned mission
• 5 years from Earth to Jupiter
• 1 year science mission
Arrives 5 July 2016
• Science objectives
– Determine O2 abundance in Jupiter’s atmosphere
– Better estimate of Jupiter’s core mass
– Precisely map Jupiter’s interior mass distribution
– Precisely map Jupiter’s magnetic field
– Map variations in atmospheric properties
– Jupiter’s polar magnetosphere & aurorae
– Measure general relativistic orbital frame-dragging
Juno’s Scientific Instruments
• Microwave radiometer
• Jovian Infrared Auroral Mapper
• Magnetometer
• Gravity Science
• Jovian Auroral Distribution Experiment
• Jovian Energetic Particle Detector Instrument
• Radio and Plasma Wave Sensor
• Ultraviolet Imaging Spectrograph
• JunoCam
Juno’s Route to Jupiter
http://upload.wikimedia.org/wikipedia/commons/b/ba/Juno%27s_interplanetary_trajectory.jpg
The Juno Spacecraft at Jupiter
http://upload.wikimedia.org/wikipedia/commons/b/b3/Juno_Mission_to_Jupiter_%282010_Artist%27s_Concept%29.jpg
The Juno Spacecraft 33 Orbits
http://upload.wikimedia.org/wikipedia/en/3/39/Juno_trajectory_through_radiation_belts.png
Juno’s Mission at Jupiter
• Polar orbit
– Highly elliptical
• Spend minimum time in Jupiter’s radiation belts
• Planned 33 orbits
• Juno de-orbited to crash into Jupiter
– Possibility of an extended mission
• Mainly an issue of fuel for orientation thrusters
Important Concepts: Jupiter
•
Jupiter data
•
– ~ 11.2 times Earth’s diameter
– ~ 318 times Earth’s mass
– Comet Shoemaker-Levy 9
• 23 fragments < 1 km in diameter
– Galileo Probe spacecraft
• ~ 2.5 times the mass of all planets
•
•
• Almost same composition as the Sun
Jupiter’s cloud details
– Prominent cloud belts & zones
– Prominent spots
• Great Red Spot
• White & brown ovals
Jupiter’s four-layer internal structure
–
–
–
–
Distinctive features
– Axial rotation period of ~ 10 hours
– Solar System’s most colorful clouds
– Composed mostly of H & He
•
• 1 tiny spacecraft for ~ 1 hour
Jupiter as seen from Earth
– Distinctly oblate shape
– Distinctive cloud bands & storms
– Four extremely obvious moons
•
Jupiter’s deeper atmosphere
•
Ordinary gaseous hydrogen & helium
Helium & liquid metallic hydrogen
Liquid “ices” (H2O, CH4 & NH3)
Rocky & metallic core
Jupiter’s magnetosphere
– Magnetic field strength ~ 14 x Earth’s
• Circulating liquid metallic hydrogen
• Very fast axial rotation
– Magnetic field size
• Width of ~ 210 x Jupiter’s diameter
• Length of ~ 6 AU (past Saturn’s orbit)
– Deflates quickly due to solar wind