Download File - Mrs. Phillips` Physical Science Webpage

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Jovian Planets
• All of the jovian planets were visited by the
Voyager probes in the 1970s and 80s
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Jovian Planets
• None of the jovian planets have a solid surface
of any kind – their gaseous surfaces just get
hotter and more dense with depth due to
pressure of the overlying layers, eventually
becoming liquid in the interior.
• Jupiter, Saturn and Neptune have significant
internal heating which impacts the behavior and
appearance of their atmosphere.
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Jovian Planets
• With no surface to tie down gas flow, the different
parts of the atmosphere flow at different speeds –
differential rotation.
– On Jupiter, the equatorial regions rotate every 9h50m and
higher regions take 6 min longer.
• http://www.youtube.com/watch?v=YgtuaQWdcGA
– On Saturn the difference is 26 minutes, with equatorial
rotating more rapidly.
– On Uranus the difference is 2 hours with the poles
rotating more rapidly
– On Neptune, the difference is 6 hours, and again, the
poles rotate more rapidly.
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Jovian Planets
• All jovian planets have strong magnetospheres
and emit radiation at radio wavelengths.
– The strength of the radio emissions varies with time
and is periodic – assumed to match the rotation of
the planets’ interior, where the magnetic field arises.
– There is no apparent relationship between interior
rotation rates and exterior rotation rates.
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Jupiter
• Jupiter is the 3rd brightest object in the night sky
(after the Moon and Venus, respectively)
• It is so massive, that there is a myth that it was
actually a failed star...Could Jupiter Become a Starhttps://www.youtube.com/watch?v=v9HtCAHv54E
• Using a small telescope one can see the
Galilean moons of Jupiter and the striped
gaseous surface
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Jupiter - Atmosphere
• Jupiter’s most striking features are it’s
multicolored bands and the Great Red Spot.
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Ganymede’s
shadow in the
GRS
Credit Hubble,
April 21, 2014
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Jupiter - Atmosphere
• What causes the colors? We don’t know.
– The most abundant gas in the atmosphere is
atmospheric hydrogen (86%), then helium (almost
14%) and then trace amounts of atmospheric
methane, ammonia, sulfur, phosphorous and water
vapor – none of which can account for the many
colors.
• Water vapor & ammonia = white clouds, so….
– Perhaps chemical process in the turbulent atmosphere
causes them, powered by internal heat, solar UV,
aurorae in the magnetosphere and lightening
discharges
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Jupiter - Atmosphere
• The banded structure is believed to
be caused by convection currents in
the planet's atmosphere.
• Lighter-colored zones alternate
with darker belts that vary in
intensity and latitude.
• Voyager sensors indicated that the
belts were areas of lower pressure
(sinking) and zones areas of higher
pressure(rising), but Cassini
contradicted this and no resolution
has been reached.
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Jupiter -Atmosphere
• Because of the rapid rotation, the high and low
pressure systems wrap all the way around the planet.
• There are strong east-west winds that lie under the
bands, called the zonal flow.
• There are at least 30 of these jet streams on
Jupiter, with average speeds of about 300mph
(482km/h).
• The flow speed decreases toward the poles, and
near the poles, where the flow disappears, the
banding also disappears.
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Jupiter - Weather
The Great Red Spot appears to be a hurricane that has
raged on for hundreds of years – at least since we first saw
the planet
There is another spot, Oval BA, discovered in 2008, which
grew and then got eaten by the GRS.
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Jupiter Weather
apodaca.nasa.gov
• The GRS rotates around the
planet at a speed similar to
the rotation of the planet's
interior, so the storm must
reach very deeply into the
planet.
• Alternating east and west
zonal flows keep the GRS
confined and give support to
the idea that the storm is
powered by Jupiter's
massive atmospheric
motion.
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Jupiter - Weather
• There are many other storms on the
planet...some are colored by the cloud tops, and
the "brown oval" is a hole in the overlying
clouds.
jpl.nasa.gov
garybrandastrology.com
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Jupiter - Weather
• Perhaps spot color has to do with size and
intensity of storm....smaller are white tipped, but
the larger ones seem to turn red....possibly the
cloud cover is lifted higher up where interaction
with UV radiation causes chemical reactions
changing the color.
• Supporting evidence of this came from three
small white spots that merged into one larger
one, and turned red.
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Jupiter
• Jupiter has rings!
• In 1979, Voyager 1 was the first to send back
photographic evidence of rings around Jupiter,
and Voyager 2 was immediately programmed
for a flyby to get a better look.
http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vg2_p21779.html
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http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vg1_p21258.html
Jupiter
• There are three ring systems: the
innermost Halo Ring, the Main
Ring and two Gossamer Rings.
• The Main Ring is only visible
when seen from behind Jupiter,
looking back toward the Sun
and lit by the Sun’s light.
• Galileo confirmed that the Main
Ring was made up from
material from the moons
Adrastea and Metis, mostly
Adrastea, through meteor
impacts.
• The
composition of
Adrastea is
unknown.
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Jupiter’s Ring
Solar radiation and
collisions with charged
particles trapped in
Jupiter’s magnetic field
exert a friction on the ring
dust that will eventually
cause the dust to drift
into the atmosphere
Jupiter has a system of
rings made of tiny particles
of rock dust and held in
orbit by Jupiter’s gravity
To maintain the rings,
new dust must be
provided from the Jovian
moons
Internal Structure - Jupiter
• Temperature and pressure increase with depth
• At a depth of a few thousand kilometers, the
gaseous atmosphere on Jupiter makes a
gradual transition to liquid.
• At around 20,000km, the pressure is about
3million x the atmospheric pressure on Earth,
causing the liquid hydrogen to compress in a
metallic state, with similar properties to liquid
metals on Earth.
• ***Excellent conductor of electricity***
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Internal Structure - Jupiter
• Jupiter’s equator has a bulge thanks to its rotation
– he radius at the equator exceeds the poles by 7%
• Calculations show that a composition of only
hydrogen and helium should result in an even
greater disparity than that….the core is indicated to
be as much as 10x the mass of Earth.
• Actual composition is obviously unknown but
theorized to be composed of similar materials to
the terrestrials – molten, maybe semisolid, rock.
• Because of the incredible pressure, the core must
be very compressed.
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Internal Heating
• With a core temperature of about 30,000K
Jupiter emits about twice as much heat as it
receives from the Sun….possibly excess energy
left over from the planet’s formation.
• In the past, Jupiter may have been much hotter
than it is now and the heat is slowly leaking
out.
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Magnetospheres
• Jupiter has the
strongest magnetic
field in the solar
system thanks to its
rapid rotation and
extensive region of
highly conduct
• Jupiter’s
magnetosphere is
HUGE!
• 20,000 x Earth’s
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Magnetospheres
• Jupiter sends particles from its magnetosphere into
its upper atmosphere forming aurorae much larger
and more energetic than those that we experience
on Earth,
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Jupiter - Missions
• Most of our detailed information we have on
Jupiter comes from the space missions past and
to the planets.
– The two Voyager probes, launched, in 1977 reached
Jupiter in March and July of 1979.
• Sounds of Jupiter
– Galileo launched in 1989 and arrived in 1995, needing
gravity assists from Venus and Earth to reach Jupiter.
• Mission was to study the atmosphere of Juipter and its moon
system.
• To end in 1997 but extended to 2003 when it was crashed
into the surface.
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Jupiter - Missions
• Cassini was launched
in 1997 to study
Saturn, but spent 6
months viewing
Jupiter during the first
months of 2001.
• Juno will reach
Jupiter in 206 and will
hopefully answer
many questions
regarding the Jovian
planets.
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The Moons of Jupiter
Io
Europa
Ganymede
Callisto
• Jupiter currently has 63 natural satellites or moons
• Number changes frequently as more are
discovered
• Four innermost moons are called the Galilean
Moons
The Moons of Jupiter
Io
Europa
Ganymede
Callisto
• Except for Europa, all are larger than the
Moon
• Formed in a process similar to the formation of
the Solar System – the density of these
satellites decreases with distance from Jupiter
Io
• Gravitational tidal forces
induced from Jupiter and
Europa keeps Io’s interior
hot
• Volcanic plumes and lava
flows are the result
Europa
• Very few craters
indicate interior
heating by Jupiter and
some radioactive
decay
• Surface looks like a
cracked egg indicating
a “flow” similar to
glaciers on Earth
• Heating may be
enough to keep a layer
of water melted below
the crust
Ganymede and Callisto
Look like our Moon with
grayish brown color and
covered with craters
However, their surfaces
are mostly ice – whitish
craters a very good
indication of this
Callisto may have
subsurface liquid water
Ganymede is less
cratered than Callisto
indicating maria-type
formations although
tectonic movement cannot
be ruled out
Other Observations
Io
•
•
Europa
Ganymede
Callisto
Galilean average densities • Rest of Jupiter’s moons are
indicate their interiors to be
much smaller than the
composed mainly of rocky
Galilean satellites and they
material
are cratered
Differentiation may have
• Outermost moons have
allowed iron to sink to core
orbits that have high
inclinations suggesting that
they are captured asteroids
Io – orbits
every 1.8
days
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Saturn
First close pass by Pioneer at 13,000 miles. Discovered
the F-ring. Pioneer is still transmitting from somewhere
toward the center of the Milky Way Galaxy. 34
Saturn
• There are three cloud layers in Saturn’s
atmosphere with an overall thickness about 3
times the thickness of Jupiter’s cloud
cover…..and each cloud layer is thicker than its
counterpart on Jupiter as well…..why?
• The thicker clouds also result in fewer gaps and
holes in the to layer so that we rarely see below
to the more colorful levels below, which is why it
appears so uniformly yellowish.
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Saturn
http://www.astronomy.com/~/link.aspx?_id=59a77baa-117f-4cd8-b887-652df196ad50
• Wind speed on Saturn is much faster than on
Jupiter, reaching speeds of 932 mph (1500 km/s).
• East-west zonal flow is stable, although there are
fewer east/west alterations.
• There are several storms on Saturn, but may
simply be hidden under the upper cloud layers.
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Cassini has observed
Saturn
Storm Alley – this
area of cyclonic
rotation, where
colder surface gases
are drawn downward
into the warmer
interior only occurs in
the southern
hemisphere, not in
the northern.
Hmmm…..
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Saturn
The hexagon surrounding a maelstrom at Saturn’s
north pole is another puzzle – wind speeds reach
530 km/h inside and 500 km/h outside, butt the
hexagon does not appear to move except with the
planet’s rotation.
http://saturn.jpl.nasa.gov/multime
dia/videos/movies/PIA17652bwsmall.gif
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Picture from
Cassini –
from 605
million miles
away
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Saturn
• Saturn’s dragon storm has
remained in one location
since 2004, with winds up to
1056 mph (1700 km/h)
• Continues lightening flashes
1000 x more powerful than
anything produced on Earth.
• Seems to be rooted to a
specific location on the
surface – but why if there is
no solid surface?
• The radio emissions from
the storms are so clock-like
that they are used to judge
the planet’s rotation rate
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below the clouds.
http://www.universetoday.com/87269/the-sights-and-sounds-of-saturns-super-storm/
Seasons of Saturn
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Internal Structure - Saturn
• Saturn has the same internal structure, but different
relative proportions from Jupiter.
• Thinner metallic hydrogen layer
• Thicker central core (inferred from greater polar
flattening), about 15x the Earth’s mass
• Saturn’s overall mass is much less than Jupiter’s,
resulting in a much lower core temp, pressure and
density – close to that of the center of Earth.
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Internal Heating
• Saturn also has an internal energy source – it
radiates about 3x the energy it receives from the
Sun.
• Since it is smaller than Jupiter, it should have
cooled more quickly, so the original heat supply
should have been used up long ago….so why all
the excess?
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Internal Heating
• Remember the lack of atmospheric helium (7%
compared to 14% for the other jovians)?
• At high temps & pressures (Jupiter), liquid helium
dissolves in liquid hydrogen.
• Saturn’s temps are lower, so helium does not
dissolve as easily and instead forms droplets….it
condenses out like rain does on Earth, sinking into
the interior, compressing the gravitational field and
heating it up.
• When the helium rain stops, the core should cool and
the amount of radiation it emits should equal out the
radiation received from the Sun.
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Magnetospheres
• Saturn also has a strong magnetic field and
magnetosphere.
• Smaller mass of the metallic hydrogen zone
results in much less strength at the cloud topss –
1/20 of Jupiter’s.
• Contains the ring system and most of its moons.
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Saturn - Cassini
• http://saturn.jpl.nasa.gov/interactive/missiontimeline/
• Cassini launched in Sept 1997, and, after a 6 month
visit to Jupiter at the first of 2001,entered orbit around
Saturn in June 2004.
• It will end its mission on Sept 15, 2017 by entering the
atmosphere.
• The Huygens probe was launched from Cassini and
landed on the moon Titan in the winter of 2004/5 and
sent back several pictures and data that is being
analyzed.
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The Rings of Saturn
• Rings are wide but thin
• Main band extends from about 30,000 km above its atmosphere to
about twice Saturn’s radius (136,000 km)
• Faint rings can be seen closer to Saturn as well as farther away
• Thickness of rings: a few hundred meters
• Main band is made up of the visible A, B and C rings, from outside in
Ring Structure
• Rings not solid, but
made of a swarm
of individual bodies
• Sizes range from
centimeters to
meters
• Composition mainly
water, ice, and
carbon compounds
and is not uniform
across rings
Ring Structure
• Large gaps due to
resonances with
Saturn’s moons located
beyond the rings
• Narrow gaps due to
complex interaction
between ring particles
and tiny moons in the
rings
The rings of Saturn
The E Ring is formed from water ice droplets from
the geysers on Enceladus and last until they strike
another moon or get blown away from the planet.
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The Phoebe Ring
Discovered when Iapetus (an
icy, bright white moon) was
observed moving through
some substance that was
causing the leading edge to
turn dark.
Absorbs sunlight, but easily
seen by infrared imaging with
NASA’s WISE spacecraft, as
above.
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A & F Ring, Encke Gap with Titan in background…and tiny Epimetheus too! – Cassini,2014
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The Roche Limit
• Any object held together solely by gravity will
break apart by tidal forces if it gets too close to
the planet.
• Distance of breakup is called the Roche limit
and is 2.44 planetary radii, if object and planet
have the same density
• All planetary rings lie near their planet’s Roche
limit… implying what?
• Existence of side-by-side ringlets of different
compositions indicates rings supplied by varied
comets and asteroids
• Objects bonded together chemically will survive
Roche limit
TheRocheLimit
Saturn’s Moons
• Saturn has several large moons and many more
smaller ones
• Like Jupiter, most of the moons form a mini-solar
system.
• Saturn’s moons have a smaller density than those
of Jupiter indicating interiors must be mostly ice
• Most moons are inundated with craters, many of
which are surrounded by white markings of
shattered ice
• The moons also have several surface features that
have yet to be explained
Saturn’s Moons
Saturn
• Tethys the
larger of the
three
• Hyperion the
the left
• Prometheus,
whose gravity
helps define
the edge of
the F-ring
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Surface of Enceledes, taken by Cassini, October 14, 2015
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Enceledes, floating above Saturn’s Rings, Cassini, July 29, 2015
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Prometheus
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Titan
• Saturn’s largest
moon
• Larger than
Mercury
• Mostly nitrogen
atmosphere
• Solid surface with
liquid oceans of
methane
• The Huygens
Probe landed on
the surface
Images from Titan’s Surface
Dionne transiting
Saturn
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Uranus
• Uranus was
discovered in 1781
by William Herschel
when he was
mapping the stars
with a 6” telescope.
• First described as “a
curious either
nebulous star or
perhaps a comet”
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After
George III
Trying to
gain favor
with the
ruling
monarch.
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Uranus
• The object moved relative to the stars, but too
slowly to be a comet.
• Though barely visibly to the naked eye, even with a
large optical telescope, it would appear a tiny, pale,
slightly greenish disk.
• Apparently featureless atmosphere.
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Uranus
• The axial tilt of Uranus is 98˚ …. No one knows
why. Catastrophic collision? No way to find out
either.
• Since the north pole lies below the ecliptic
plane, the planet’s rotation is considered to be
retrograde.
• During part of its orbit, the north pole points
directly at the Sun; half a Uranian year later, the
south pole points directly at the Sun.
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Uranus
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Uranus - Weather
• Uranus is the coldest planet in the
solar system, with temperatures
reaching -371 F (-224 C).
• Cloud layers form only at lower,
warmer levels, so to see any
atmospheric structure, you have to
look much deeper, and the
stratospheric haze makes that
difficult.
• Clouds and flow patterns appear to
move around the planet in the sane
direction as the planet’s rotation,
with wind speeds of about 125-310
mph (200-500 km/hr).
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Uranus
Storm Surge, pictures from the Keck Observatory
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Uranus
One of Uranus’ moons,
Miranda.
• Unusual topography
believed to be caused by
tidal heating, resulting from
an eccentric orbit around
Uranus, causing
temperatures within the
moon to increase and
decrease, driving convection
currents.
• Appears to have been torn
apart and reassembled
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Neptune
• Astronomers discovered quickly that there was a large
discrepancy in the expected orbit - perturbation.
• Although the Sun’s gravitational pull dominated, there was a
small deviation causing a measureable gravitational
force….there must be another planet beyond Uranus.
• It took two years for John Adams to mathematically
calculate the new planet’s mass and orbit; about 9
months later another mathematician independently
found the same answer (Urbain Leverrier) and the two
are credited with the discovery of Neptune.
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Neptune
• Neptune CANNOT be seen at all without a
magnification, but is visible even with good
binoculars.
• Bluish dot with a few visible
features…resembles a blue-tinted Jupiter
Sailing Past Neptune’s
Moon Triton
https://www.youtube
.com/watch?v=6ByGD
B8dM_c
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Neptune - Weather
• Neptune is farthest from the Sun, but its internal heat
keeps it slightly warmer than Uranus.
• Slightly thinner atmospheric haze than Uranus and
less dense cloud layers
• Neptune has the most violent winds in the solar
system, reaching 1500 mph (2414 km/h).
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Neptune - Weather
• The Great Dark Spot just south of the equator was
discovered by Voyager 2 in 1989 and was about the
size of Earth.
• By the time Hubble focused on Neptune to study the
planet in the 90s, the Great Dark Spot was gone and a
new spot, comparable
in size was visible in
the northern
hemisphere.
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Neptune - Weather
Where these spots come from, how they age and
why/how they die is not understood.
They are holes in the upper atmosphere.
They are likely powered by the same processes
that cause the Great Red Spot on Jupiter.
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Rings of Neptune
Neptune, like the other
giant planets, has rings
They are probably debris
from satellites or comets
that have broken up
They contain more dust
than the Saturn/Uranus
rings
The rings are not
distributed uniformly
around the ring indicating
they are relatively new
Uranus and Neptune Coloring
• Again, the primary gas for all of the jovian planets is molecular
hydrogen and next up is helium.
• Ammonium, which was present on both Jupiter and Saturn, is
not observed in any measurable amount on either Uranus or
Neptune, most likely because at the much colder temperatures,
it would exist as ice crystals, not gas.
• Methane is more abundant on Uranus and Neptune,
accounting for their blue coloring….
• Methane absorbs longer wavelengths, so the light reflected
lacks red, orange and yellow.
• The greater the concentration of methane, the bluer the
appearance; Uranus has 2% and Neptune has 3% so
which would be bluer?
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Internal Structure – Uranus & Neptune
• The internal pressures of Uranus and Neptune are
low enough that hydrogen remains a gas the core.
• In theory, the interior of these planets may have
high-density layers of highly compressed water
clouds.
• It is also possible that ammonia may be dissolved
in the water producing an electrically conducting
layer that might explain the magnetic fields.
• But, WE DON’T KNOW. 
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Internal Structure – Uranus & Neptune
• We infer theories on the cores of Uranus and
Neptune based on their densities…
• Low mass so the hydrogen and helium should not
be as compressed, but their average densities are
greater than Saturn’s – closer to Jupiter’s average
density.
• So, their cores must be closer to Earth-sized with
about 10x the mass with compositions similar to the
other two jovians.
• We won’t learn much of anything more about
any of the until Juno arrives to study Jupiter in
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2016.
Internal Heating
• Uranus has no internal heating source, radiating
just as much heat as it receives from the Sun,
having lost its initial heat to space long ago.
• Neptune DOES have an internal heat source,
emitting 2.7x as much heat as it receives.
• This results in the convection currents which
drive the cloud belts that Neptune has and
Uranus does not.
• WE DON’T KNOW WHY.
• Perhaps the relatively high concentration of methane
helps to insulate it?
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Magnetospheres
• Uranus and Neptune have magnetic fields
comparable to Saturn.
• Magnetospheres are populated by ions captured by
solar winds or from hydrogen gas escaping from
the planets below.
• **The fields are not aligned with the rotation axes
and are very offset from the centers – no idea why.
Uranus
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