April 10, 2006 Astronomy 2010 1 Giant Planets. April 10, 2006Astronomy 20102 Jupiter Saturn UranusNeptune Jovian Worlds.

April 10, 2006April 10, 2006 Astronomy 2010Astronomy 2010 11Giant PlanetsGiant Planets

April 10, 2006April 10, 2006 Astronomy 2010Astronomy 2010 22

Jupiter

Saturn

Uranus Neptune

Jovian WorldsJovian Worlds


ExplorationExploration First spacecrafts: pioneer 10 (1972) & 11 (1973).First spacecrafts: pioneer 10 (1972) & 11 (1973).

Can we navigate through the asteroid belt? Can we navigate through the asteroid belt? What are the radiation hazards near the planets?What are the radiation hazards near the planets?

Pioneer 10 flew by Jupiter 1973 and flew out the solar system.Pioneer 10 flew by Jupiter 1973 and flew out the solar system. Pioneer 11 flew by Jupiter 1974 and was deflected towards Pioneer 11 flew by Jupiter 1974 and was deflected towards

Saturn which it reached in 1979.Saturn which it reached in 1979.


ExplorationExploration

Voyager 2 Voyager 1 & 2 (launched 1977)Voyager 1 & 2 (launched 1977) Highly productive MissionsHighly productive Missions Carried 11 scientific instruments including cameras and Carried 11 scientific instruments including cameras and

spectrometers, devices to measure the magnetospheresspectrometers, devices to measure the magnetospheres Voyager 1Voyager 1

Reached Jupiter 1979 and Saturn 1980Reached Jupiter 1979 and Saturn 1980 Used gravity assist towards SaturnUsed gravity assist towards Saturn

Voyager 2 Voyager 2 Reached Jupiter four month later than Voyager 1Reached Jupiter four month later than Voyager 1 Reached Saturn 1981, Uranus 1986, Neptune 1989Reached Saturn 1981, Uranus 1986, Neptune 1989

Multiple Flybys possible thanks to approximate Multiple Flybys possible thanks to approximate alignment of the planets - occurs once in 175 yearsalignment of the planets - occurs once in 175 years

Voyager 2Voyager 2


ExplorationExploration

Galileo space probeGalileo space probe Launched 1989Launched 1989 Reached Jupiter December Reached Jupiter December

19951995 Deployed a small entry Deployed a small entry

probe for a direct study of probe for a direct study of Jupiter’s atmosphereJupiter’s atmosphere

Sept. 2003, probe sent into Sept. 2003, probe sent into Jupiter’s atmosphere to end Jupiter’s atmosphere to end its mission.its mission.

Cassini Cassini Launched 1997Launched 1997 Reached Saturn in 2004, Reached Saturn in 2004,

now in orbit.now in orbit. Will deploy entry probe for Will deploy entry probe for

Titan in Jan 2005Titan in Jan 2005

Galileo Space ProbeGalileo Space Probe


Mass 339 kgMass 339 kg Plunged at shallow angle into Plunged at shallow angle into

Jupiter at speed of 50 km/s.Jupiter at speed of 50 km/s. Slow down by friction against Slow down by friction against

the Jovian atmosphere, the Jovian atmosphere, temperature of shield to temperature of shield to 1500015000ooCC

Speed dropped to 2500 km/hSpeed dropped to 2500 km/h Deployed parachute for actual Deployed parachute for actual

entry in the atmosphereentry in the atmosphere Transmission of data to orbiter Transmission of data to orbiter

– retransmission to Earth– retransmission to Earth 57 minute descent/recording57 minute descent/recording 200 km downward/500 km 200 km downward/500 km

sidewardsideward

Galileo – Jupiter Entry ProbeGalileo – Jupiter Entry Probe


Some Scientific results of the Galileo missionSome Scientific results of the Galileo mission The discovery of a satellite (Dactyl) of an asteroid (Ida). The discovery of a satellite (Dactyl) of an asteroid (Ida). Confirmation of the existence of a huge ancient impact basin in the southern part of Confirmation of the existence of a huge ancient impact basin in the southern part of

the Moon's far side (inferred from Apollo data but never before mapped). the Moon's far side (inferred from Apollo data but never before mapped). Evidence of more extensive lunar volcanism than previously thought. Evidence of more extensive lunar volcanism than previously thought. Discovery of an intense interplanetary dust storm (the most intense ever observed). Discovery of an intense interplanetary dust storm (the most intense ever observed). Discovery of an intense new radiation belt approximately 50,000 km (31,000 miles) Discovery of an intense new radiation belt approximately 50,000 km (31,000 miles)

above Jupiter's cloud tops. above Jupiter's cloud tops. Jovian wind speeds in excess of 600 kilometers per hour (> 400 mph) were detected. Jovian wind speeds in excess of 600 kilometers per hour (> 400 mph) were detected. Far less water was detected in Jupiter's atmosphere than estimated from earlier Far less water was detected in Jupiter's atmosphere than estimated from earlier

Voyager observations and from models of the Comet Shoemaker-Levy 9 impact. Voyager observations and from models of the Comet Shoemaker-Levy 9 impact. Far less lightning activity (about 10% of that found in an equal area on Earth) than Far less lightning activity (about 10% of that found in an equal area on Earth) than

anticipated. The individual lightning events, however, are about ten times stronger on anticipated. The individual lightning events, however, are about ten times stronger on Jupiter than the Earth. Jupiter than the Earth.

Helium abundance in Jupiter is very nearly the same as its abundance in the Sun Helium abundance in Jupiter is very nearly the same as its abundance in the Sun (24% compared to 25%). (24% compared to 25%).

Extensive resurfacing on Io due to continuing volcanic activity since the 1979 Extensive resurfacing on Io due to continuing volcanic activity since the 1979 Voyagers fly-bys. Voyagers fly-bys.

Preliminary data support the evidence of magnetic fields for both Io and Ganymede. Preliminary data support the evidence of magnetic fields for both Io and Ganymede. Evidence for liquid water ocean under Europa's ice.Evidence for liquid water ocean under Europa's ice.

Jovian PlanetsJovian Planets - Basics - Basics Large distance from the sun.Large distance from the sun. Long period.Long period. Jupiter/Saturn similar in composition + internal structure.Jupiter/Saturn similar in composition + internal structure. Uranus/Neptune smaller, differ in composition and structure.Uranus/Neptune smaller, differ in composition and structure.

Basics Properties of the Jovian Planets

Planet Distance (AU)

Period (years)

Diameter (km)

Mass (Earth=1)

Density (g/cm3)

Rotation (hours)

Jupiter 5.2 11.9 142800 318 1.3 9.9

Saturn 9.5 29.5 120540 95 0.7 10.7

Uranus 19.2 84.1 51200 14 1.2 17.2

Neptune30.1 164.8 49500 17 1.6 16.1


AppearanceAppearance Only the upper atmosphere of the giant planets is Only the upper atmosphere of the giant planets is

visible to usvisible to us Composed primarily of hydrogen and helium gasComposed primarily of hydrogen and helium gas Jupiter/Saturn Jupiter/Saturn

Uppermost clouds made of ammonia crystals (NHUppermost clouds made of ammonia crystals (NH33)) NeptuneNeptune

Methane (CHMethane (CH44)) UranusUranus

no clouds, featureless hazeno clouds, featureless haze


RotationRotation How does one determine the rotation rate of the How does one determine the rotation rate of the

giants?giants? On Jupiter:On Jupiter:

11stst option: Use dynamic surface features (storms). option: Use dynamic surface features (storms). However the cloud rotation may have nothing to do with the However the cloud rotation may have nothing to do with the

rotation of the mantle and core…rotation of the mantle and core… 22ndnd option: look at periodic variations of radar waves option: look at periodic variations of radar waves

associated with the magnetic field produced deep inside the associated with the magnetic field produced deep inside the planet.planet.Rotation 9h 56 min.Rotation 9h 56 min.

Same technique used to measure the rotation of other Same technique used to measure the rotation of other giant planets:giant planets: Saturn : 10h40 m.Saturn : 10h40 m. Uranus/Neptune : ~ 17 hours.Uranus/Neptune : ~ 17 hours.

Jupiter Jupiter tilted by 3tilted by 3oo

No seasons to speak of.No seasons to speak of.

SaturnSaturnTilted by 27Tilted by 27oo

Long seasonsLong seasons

NeptuneNeptuneTilted by 27Tilted by 27oo

Long seasons.Long seasons.

Seasons on the GiantsSeasons on the Giants

UranusTilted by 98o Practically orbiting on its sideRings + satellites follow same pattern21 year seasons!!!Why this odd tilt? Giant impact!


Giant Planets – Giant PressureGiant Planets – Giant PressureGiant planets composed mainly of H, He, but…Giant planets composed mainly of H, He, but…Because of its enormous size, hydrogen and Because of its enormous size, hydrogen and

helium in the center of Jupiter is compressed helium in the center of Jupiter is compressed enormously –.enormously –.Estimated pressure: 100 million bars.Estimated pressure: 100 million bars.Central density of 31 g/cmCentral density of 31 g/cm33..

Earth by contrast has 4 million bars and 17 g/cmEarth by contrast has 4 million bars and 17 g/cm33 in its in its center.center.

Giant Planet implies Giant Pressure!!Giant Planet implies Giant Pressure!!


Consequences of the PressureConsequences of the Pressure

Few 1000 km below the surface, hydrogen is in Few 1000 km below the surface, hydrogen is in a liquid statea liquid state

Still deeper, the liquid is further compressed Still deeper, the liquid is further compressed and begins to act like a metal.and begins to act like a metal.

On Jupiter part of the interior is metallic On Jupiter part of the interior is metallic hydrogen!hydrogen!

Saturn is less massive – most of its interior is Saturn is less massive – most of its interior is liquid – but not metallic.liquid – but not metallic.

Neptune/Uranus are probably too small to Neptune/Uranus are probably too small to liquefy hydrogenliquefy hydrogen


More about CompositionMore about Composition

The planets also have a core composed of heavier materialsThe planets also have a core composed of heavier materials Possibly the original rock/ice bodies that formed before gas were Possibly the original rock/ice bodies that formed before gas were

abundantly captured by the planets.abundantly captured by the planets.


Internal Heat Source (1)Internal Heat Source (1) Because of their large sizes, all giant planets were Because of their large sizes, all giant planets were

strongly heated during their formation - Jupiter was the strongly heated during their formation - Jupiter was the hottesthottest

Some of the primordial heat still remainsSome of the primordial heat still remains Giant planets may also generate energy internally by Giant planets may also generate energy internally by

slowly contracting slowly contracting Even a small amount of shrinkage can generate significant Even a small amount of shrinkage can generate significant

heatheat Raises the temperature of the core and atmosphere above Raises the temperature of the core and atmosphere above

the temperature due to the Sun energy supply. the temperature due to the Sun energy supply. Jupiter has the largest internal source of energyJupiter has the largest internal source of energy

4x104x101717 Watts Watts A cross between a planet (like earth) and a starA cross between a planet (like earth) and a star Internal heat is primordial heatInternal heat is primordial heat


Magnetic Magnetic FieldsFields

All four giant planets have All four giant planets have strong magnetic fields and associated magnetospheresstrong magnetic fields and associated magnetospheres

The magnetospheres are large – extend for millions of km in The magnetospheres are large – extend for millions of km in spacespace

Jupiter’s field was discovered in the late 1950’s Jupiter’s field was discovered in the late 1950’s Radio waves detected from JupiterRadio waves detected from Jupiter Electrons circulating in the magnetosphere produce the radio waves by a Electrons circulating in the magnetosphere produce the radio waves by a

process called synchrotron emission.process called synchrotron emission. Magnetic fields of Saturn, Uranus, and Neptune discovered by Magnetic fields of Saturn, Uranus, and Neptune discovered by

flyby spacecraft.flyby spacecraft.


MagnetospheresMagnetospheresJupiter’s magnetic field not aligned with its axis Jupiter’s magnetic field not aligned with its axis

of rotation. – tipped by 10of rotation. – tipped by 10oo

Uranus/Neptune have tilts of 60Uranus/Neptune have tilts of 60oo and 55 and 55oo..Saturn’s field is perfectly aligned with its axis of Saturn’s field is perfectly aligned with its axis of

rotation.rotation.


AtmospheresAtmospheres

The part of the planets accessible to direction The part of the planets accessible to direction observation.observation.

Dramatic examples of weather patterns.Dramatic examples of weather patterns.Storms on these planets can be larger than Earth!Storms on these planets can be larger than Earth!


Atmospheric CompositionAtmospheric CompositionMethane (CHMethane (CH44) and ammonia (NH) and ammonia (NH33) were first ) were first

believed to be the primary constituents of the believed to be the primary constituents of the atmospheres.atmospheres.

We know today that hydrogen and helium are We know today that hydrogen and helium are actually the dominant gases.actually the dominant gases.First based on far-infrared measurements by First based on far-infrared measurements by

VoyagerVoyagerLess helium in Saturn’s atmosphere Less helium in Saturn’s atmosphere

Precipitaion of Helium? Energy Source of Precipitaion of Helium? Energy Source of Saturn?Saturn?

Best measurements of composition by Galileo Best measurements of composition by Galileo spacecraft (1995) upon atmosphere entry.spacecraft (1995) upon atmosphere entry.


Clouds and Atmospheric StructureClouds and Atmospheric Structure

Jupiter’s clouds are Jupiter’s clouds are spectacular in color and spectacular in color and size.size. Color: orange, red, brownColor: orange, red, brown Fast motionFast motion

Saturn is more “subdued”: Saturn is more “subdued”: clouds have nearly clouds have nearly uniform butterscotch hue.uniform butterscotch hue.


Winds and WeatherWinds and Weather Many regions of high/low pressureMany regions of high/low pressure

Air flow between these regionsAir flow between these regionsSets up wind patterns distorted by the fast rotation of the Sets up wind patterns distorted by the fast rotation of the

planet.planet.Wind speeds measured by tracking cloud patterns.Wind speeds measured by tracking cloud patterns.

Differences with EarthDifferences with Earth Giant planets spin much faster than EarthGiant planets spin much faster than Earth

Rapid rotation smears out air circulation into horizontal Rapid rotation smears out air circulation into horizontal (east-west) patterns parallel to the equator.(east-west) patterns parallel to the equator.

No solid surfaceNo solid surfaceNo friction or loss of energy – why tropical storms on No friction or loss of energy – why tropical storms on

Earth eventually die out…Earth eventually die out… Internal Heat contributes as much energy to the atmosphere Internal Heat contributes as much energy to the atmosphere

as sunlight (except for Uranus).as sunlight (except for Uranus).


What causes the winds?What causes the winds?

Coriolis Effect!Coriolis Effect!



Jupiter/Saturn WindsJupiter/Saturn Winds


Uranus/Neptune WindsUranus/Neptune WindsRather similar to the winds on Jupiter/SatrunRather similar to the winds on Jupiter/SatrunTrue on Uranus in spite of the 98True on Uranus in spite of the 98OO tilt. tilt.


StormsStorms Always present on the giant planetsAlways present on the giant planets Superimposed on the regular circulation patternsSuperimposed on the regular circulation patterns Large oval shape high-pressure regions on both Large oval shape high-pressure regions on both

Jupiter and NeptuneJupiter and Neptune Most famous: Jupiter Great Red SpotMost famous: Jupiter Great Red Spot

In the Southern hemisphereIn the Southern hemisphere 30000 km long (when Voyager flew by)30000 km long (when Voyager flew by) Present since first seen 300 years agoPresent since first seen 300 years ago Changes in size – but never disappearsChanges in size – but never disappears

From Voyager 1, 1979


Great Great RedRed Spot Spot Counterclockwise rotationCounterclockwise rotation Period : 6 daysPeriod : 6 days Similar disturbances formed Similar disturbances formed

in 1930s on Jupiterin 1930s on Jupiter Smaller circles near the red spotSmaller circles near the red spot

Cause unknownCause unknown Long lived because of Long lived because of

absence of ground, andabsence of ground, and their sizetheir size

Expected life - centuriesExpected life - centuries


Neptune Great Dark SpotNeptune Great Dark Spot First seen in 1989 by VoyagerFirst seen in 1989 by Voyager 10000 km long10000 km long 17 day period17 day period Had disappeared (faded?) in Had disappeared (faded?) in

June 1994June 1994 New dark spot seen in Nov New dark spot seen in Nov

19941994 Faded by 1995Faded by 1995

Do storms form and disappear Do storms form and disappear faster on Neptune?faster on Neptune?


Saturn SpotsSaturn SpotsLarge storms rare on SaturnLarge storms rare on SaturnAppear to be connected with the seasonsAppear to be connected with the seasonsSpot outbreaks every 30 years or so near the Spot outbreaks every 30 years or so near the

equatorequatorMost recently in 1990Most recently in 1990

April 10, 2006 Astronomy 2010 1 Giant Planets. April 10, 2006Astronomy 20102 Jupiter Saturn UranusNeptune Jovian Worlds.

Documents

reached jupiter

reached saturn

saturn voyager

exploration voyager

small entry probe

galileo space probe

magnetospheres voyager

jovian atmosphere