Download Structure of Mercury`s Interior

Mercury's Interior and Surface
Mercury, the innermost planet of the solar system, is a little bigger than the Earth's Moon. The
surface of the planet is covered with craters, like the Moon, but temperatures there can reach
over 800oF because Mercury is so close to the Sun and rotates so slowly. Scientists believe
that the interior structure of Mercury includes a metallic core, an intermediate rocky layer, and
a thin brittle crust. The composition of Mercury is probably high in iron, although surface
features indicate that volcanic activity once existed at the surface. There is little evidence of
motions near the surface of the planet now, although at earlier times during Mercury's
evolution the surface was much more active. We know relatively little about Mercury,
compared to most of the other planets, because it is relatively difficult to see and only one
spacecraft has studied the planet. An interesting fact is that Mercury has no natural satellites
or moons.
This picture shows Mercury. Mercury is the smallest
planet in our Solar System. It is also the closest
planet to the Sun. This picture was taken by the
MESSENGER spacecraft in January 2008. This color
picture shows Mercury pretty much as human eyes
would see it. Mercury is mostly gray. If you look
closely, however, you can see some shades of blue
and brown. Image courtesy of NASA/Johns
Hopkins University Applied Physics
Laboratory/Carnegie Institution of Washington.
This is an image showing the cratered surface of the
planet Mercury.
Surface of Mercury
Images of the surface of Mercury obtained by Mariner 10 showed a planet covered with
craters, looking very much like the Earth's Moon. During its three passes by the planet,
Mariner 10 took pictures of about half the surface of the planet, so we don't know what the
rest of the surface looks like. Mercury's impact craters were made early in the evolution of the
solar system, nearly 4 billion years ago, by meteorites which hit the surface. The relatively
smooth plains between craters indicates that at one point the surface was probably volcanic,
as lava flows filled in after the impacts of large objects. It appears that these plains and
heavily cratered regions are not uniformly scattered around the surface. Instead, craters are
concentrated on one part of the planet while plains dominate another part. Wrinkle ridges or
"rupes", a few km across and hundreds of km long, are also common on the surface. These
features, which can reach several km in height, were probably created as the interior of the
planet cooled and shrunk, causing the surface to collapse in and form ridges. Major surface
features include ridges, plains, and numerous large craters, the largest (about 800 mi or 1300
km across) named the Caloris Basin.
This is a mosaic of the caloris basin and its surrounding area. The
Caloris Basin is closest to the sun when Mercury is at the closest point
in its orbit to the sun. Image Courtesy of NASA
This is an image of wrinkle ridges on the surface of Mercury. The
photograph was taken by the Mariner 10 spacecraft.
Courtesy of NASA.
Structure of Mercury's Interior
Mercury has a radius of 2439 km (1524 mi), and the metallic iron-nickel core is believed to
make up about 75% of this distance. Measurements of the planet's magnetic field made by
Mariner 10 as it flew by the planet indicates that this core is likely to be hot and fluid. In
contrast with the other terrestrial planets, the rest of the planet is probably made up of a solid
rocky layer topped with a thin crust about 100 km thick. The surface of Mercury is covered
with a variety of craters formed from the impact of meteorites billions of years ago and other
features that reveal information about the evolution of the planet.
This diagram shows the internal structure of the planet Mercury.
Scientists believe that the core of Mercury is hot, liquid iron-nickel.
Mercury has no atmosphere and as a result, the surface is pocked
by craters from collisions with asteroids over billions of years.
Windows Original.
Atmosphere of Mercury
Mercury has almost no atmosphere. The planet's small size means that its gravity is too weak
to hold down a normal atmosphere. There is a very thin atmosphere around the planet.
Mercury's thin atmosphere is constantly being "blown away" into space by the pressure of
sunlight and by the solar wind. Gases are constantly being added to Mercury's atmosphere,
too. That's why it still has any atmosphere at all - even though that atmosphere is really, really
thin.
Mercury's atmosphere contains small amounts of hydrogen, helium, and oxygen. It also has
even tinier amounts of sodium, potassium, calcium, and magnesium. Some of the gas
particles come from the solar wind. Others are made by radioactive decay or when
micrometeorites smash into the surface. All of these gases are soon carried away from
Mercury by the solar wind and by Mercury's magnetic field. Atmospheric pressure at the
planet's surface is less than one trillionth of Earth's (around one nanopascal or 10-14 bar).
Temperatures at the surface range between 100 and 700 kelvins (-280° F to 800° F or -173°
C to 427° C). Lead melts at 600 kelvins! This large range in surface temperature is possible
because Mercury is so close to the Sun (a year is only 88 Earth days long) and does not have
sufficient atmosphere present to moderate the range in surface temperature.
Mercury's thin atmosphere contains hydrogen, helium, and oxygen. It also has smaller amounts of
sodium, potassium, calcium, and magnesium. This picture shows sodium near Mercury. Red and green
areas have the most sodium. Image courtesy of NASA/Johns Hopkins University Applied Physics
Laboratory/Carnegie Institution of Washington.
Venus Inside and Out
Venus is the second planet from the Sun, and is Earth's closest neighbor in the solar system.
Venus is the brightest object in the sky after the Sun and the Moon, and sometimes looks like
a bright star in the morning or evening sky. The planet is slightly smaller than Earth, and its
interior is similar to Earth. We can't see the surface of Venus from Earth, because it is
covered with thick clouds that strongly reflect sunlight. However, space missions to Venus
have shown us that its surface is covered with craters, over 1600 major volcanoes,
mountains, large highland terrains, and vast lava plains. The surface of Venus is not where
you'd like to be, with temperatures reaching more than 450C (approaching 900F - high
enough to melt lead), an atmosphere 90 times heavier than our own, and clouds of sulfuric
acid floating around to top it off! Like Mercury, Venus does not have any natural satellites or
moons.
This is a global view of the surface of Venus.
NASA/JPL
This image is a composite of the complete radar image collection obtained by the Magellan
mission. It shows craters on the surface of about 300 to 500 million years old. NASA/JPL
Inside Venus
Venus is a slightly smaller than the Earth, with a diameter 95% that of Earth (12,103 km) and
a mass 81% that of Earth. If we could walk around on the surface of the planet (without being
killed by the toxic blast furnace of an atmosphere), gravity would be close to that on the
surface of Earth.
The interior of Venus is probably similar to Earth's interior. Venus, like Earth, is one of the
terrestrial planets and is made of rock and metal. It probably has a partly molten metallic core,
a rocky mantle, and a crust. The planet rotates very slowly, taking more than 243 Earth days
to spin once on it's axis (even longer than the time it takes for Venus to orbit the Sun, about
225 Earth days). This may be the reason the planet doesn't have a magnetic field like many
of the other planets, including Earth.
The varied terrain of Venus, including volcanoes, mountains, craters, and lava flows,
suggests that the planet was once, and perhaps still is, geologically active. But basic
questions about the interior of Venus remain, such as the thickness of the lithosphere.
This is an illustration of the interior layers of Venus. Windows Original.
The Atmosphere
of Venus
This is an artist's rendition
of a column of clouds on
Venus. The temperature of
the different layers is
shown at the left.
Windows to the Universe
original image
The atmosphere of Venus
is very hot and thick. You
would not survive a visit to
the surface of the planet you couldn't breathe the
air, you would be crushed
on by the enormous
weight of the atmosphere,
and you would burn up in
surface temperatures high
enough to melt lead.
The atmosphere of Venus
is made up mainly of
carbon dioxide, and thick
clouds of sulfuric acid
completely cover the
planet. The atmosphere
traps the small amount of
energy from the sun that
does reach the surface
along with the heat the
planet itself releases. This greenhouse effect has made the surface and lower atmosphere of
Venus one of the hottest places in the solar system! If you were on the surface of the planet,
the air above you would be about 90 times heavier than the Earth's atmosphere. This is like
what a submarine experiences at 3000 ft below the surface of the Earth's ocean. The
atmosphere is composed mainly of carbon dioxide (96%), 3.5% nitrogen, and less than 1% is
made up of carbon monoxide, argon, sulfur dioxide, and water vapor.
Why should Venus and not the Earth have a hot and thick atmosphere? Some scientists call it
the Goldilocks phenomenon.
Measurements made by probes which travelled through the atmosphere have shown that the
atmospheric temperature remains nearly constant through the long dark night. Thus there are
neither significant seasons, nor daily temperature changes in the atmosphere.
Volcanic Rises
Volcanic rises are more like islands than a continents. They are broad, sloping highlands over
1000 km across. Measurements suggest that there is hot magma deep beneath these rises
that helps to buoy them up and support their mountains, as shown in this picture.
There are three particular types of volcanic rises:
• Rift-Dominated Rises
These are rises that contain two or more deep rift valleys. Atla Regio and Beta Regio
are rift-dominated rises.
• Volcano-Dominated Rises
These rises contain one or more large shield volcanoes. Western Eistla Regio and
Imdr Regio are volcano-dominated rises.
• Corona-Dominated Rises
These rises lack large rift valleys, like volcano-dominated rises. But instead of being
dominated by shield volcanoes, their surfaces are dominated by coronae. Coronadominated rises include Eastern Eistla Regio and Themis Regio.
This is a 3-D image of part of the Western Eistla Regio, Lava flows extend for hundreds of
kilometers across the fractured plains shown in the foreground. NASA/JPL
Earth's Interior and Surface
Earth, the largest and densest rocky planet, was formed about 4.5 billion years ago. The
Earth's interior is divided into four layers, which is typical of rocky planets. Each layer has
different characteristics and is made of different elements and minerals.
There are many different types of features on Earth’s surface due to the complexity of our
planet. The surface is unique from the other planets because it is the only one which has
liquid water in such large quantities. Water forms some features of Earth's surface such as
rivers, oceans, beaches and lakes. Other surface features, such as mountains, earthquakes
and volcanoes, are formed when large pieces of the Earth’s outer layer move slowly by plate
tectonics.
This is an image of the Grand Canyon in
Arizona. It is 277 miles long and up to 18 miles
across. The Grand Canyon is the largest
canyon in the world and was cut by the
Colorado River over millions of years. Some
parts are almost a mile deep. Aris Multimedia
Entertainment, Inc. 1994
Mean sea-surface salinity. Grey
shaded areas (land) exceed 36
psu (practical salinity units).
Image courtesy of NOAA
Structure of the Interior of Earth
This is an image of Earth and the interior layers. Windows Original.
Earth has a diameter of about 12,756 km (7,972 mi). The Earth's interior consists of rock and
metal. It is made up of four main layers: 1) the inner core: a solid metal core made up of
nickel and iron (2440 km diameter) 2) the outer core: a liquid molten core of nickel and iron
3) the mantle: dense and mostly solid silicate rock 4) the crust: thin silicate rock material
The temperature in the core is hotter than the Sun's surface. This intense heat from the inner
core causes material in the outer core and mantle to move around.
The movement of material deep within the Earth may cause large plates made of the crust
and upper mantle to move slowly over the Earth’s surface. It is also possible that the
movements generate the Earth's magnetic field, called the magnetosphere.
The Earth's Moon
The Earth's one natural satellite, the Moon, is more than one quarter the size of Earth itself
(3,474 km diameter). Because of its smaller size, the Moon's gravity is one-sixth of the Earth's
gravity, as we saw demonstrated by the giant leaps of the Apollo astronauts.
While there are only two basic types of regions on the Moon's surface, there are many
interesting surface features such as craters, mountain ranges, rilles, and lava plains. The
structure of the Moon's interior is more difficult to study. The Moon's top layer is a rocky solid,
perhaps 800 km thick. Beneath this layer is a partially molten zone. Although it is not known
for certain, many lunar geologists believe the Moon may have a small iron core, even though
the Moon has no magnetic field. By studying the Moon's surface and interior, geologists can
learn about the Moon's geological history and its formation.
The footprints left by Apollo astronauts will last for centuries because there is no wind on the
Moon. The Moon does not possess any atmosphere, so there is no weather as we are used
to on Earth. Because there is no atmosphere to trap heat, the temperatures on the Moon are
extreme, ranging from 100° C at noon to -173° C at night.
The Moon doesn't produce its own light, but looks bright because it reflects light from the Sun.
Think of the Sun as a light bulb, and the Moon as a mirror, reflecting light from the light bulb.
The lunar phase changes as the Moon orbits the Earth and different portions of its surface are
illuminated by the Sun.
Earth's
Atmosphere
The atmosphere is a
mixture of nitrogen
(78%), oxygen (21%),
and other gases (1%)
that surrounds Earth.
High above the planet,
the atmosphere
becomes thinner until it
gradually reaches space.
It is divided into five
layers. Most of the
weather and clouds are
found in the first layer.
The atmosphere is an
important part of what
makes Earth livable. It
blocks some of the Sun's
dangerous rays from
reaching Earth. It traps
heat, making Earth a
comfortable temperature.
And the oxygen within
our atmosphere is
essential for life.
Over the past century,
greenhouse gases and
other air pollutants
released into the
atmosphere have been
causing big changes like
global warming, ozone
holes, and acid rain.
Planet Structure
The uniquely red global surface of Mars is marked by many interesting features - some like
those on the Earth and others strangely different. The reddish color is caused by rust (iron
oxide) in the soil.
Some of these features are; volcanoes, canyon systems, river beds, cratered terrain, and
dune fields.
Of these features, the most interesting includes the apparently dead volcano Olympus Mons,
which rises 23 km (~75,000 ft) above the surrounding plains and is the highest known peak in
the Solar System. Valles Marineris is a giant canyon system that runs about 2,500 miles
across the surface of the planet and reaches depths of 6 km or 4 miles (for comparison, the
Grand Canyon is not more than 1 mile deep).
This is a mosaic of Olympus Mons, the highest
volcano on Mars. NASA
This is an image of Valles Marineris. Image from:
NASA NASA/JPL
Martian Moons
Mars has two moons Deimos and Phobos.
Lower Atmosphere
The atmosphere of Mars is much thinner than that of Earth, with a surface pressure averaging
1/100th that at the surface of the Earth. Surface temperatures range from -113oC at the winter
pole to 0oC on the dayside during summer.
Although the length of the Martian day (24 hours and 37 minutes) and the tilt of its axis (25
degrees) are similar to those on Earth (24 hours and 23.5 degrees), the orbit of the planet
about the Sun affects the lengths of the seasons the most. The atmosphere is composed
mainly of carbon dioxide (95.3%), nitrogen (2.7%), and argon (1.6%), with small amounts of
other gases. Oxygen, which is so important to us on earth, makes up only 0.13% of the
atmosphere at Mars. There is only one-fourth as much water vapor in the atmosphere.
Although small, this is thought to be enough to allow water ice to be frozen into the surface of
the planet. With so little water, clouds are rarely seen in the Martian sky. The possible role in
the past of liquid water in forming the dry river beds which we can see is still unknown,
particularly because water ice is not plentiful on the surface of the planet.
This drawing represents several features of the atmosphere on Mars including: dust storms,
an atmospheric pressure much lower than found on Earth, and a composition primarily of
carbon dioxide.
The Interior of Mars, from Mars Pathfinder
Many missions have returned data on the shape of Mars, a measurement which contributes
to an understanding of a planet's interior structure. These data first showed that Mars had a
huge bulge, now called the Tharsis Ridge. Mars Pathfinder took better data on the shape of
Mars by passing over the Martian poles instead of the around the middle.
These data suggest that Mars has a large, and solid core, as shown in the figure to the left.
(The figure is a rough drawing and is not meant to show the detailed shape of the core).
These findings help address questions which remain about Mars, and contribute to the overall
results returned by the Mars Pathfinder mission.
Scientists used to think that because the Martian surface contained so much iron, and the
Martian magnetic field was weak, that the early history of Mars was not sufficiently warm for
Mars to differentiate, and form a large solid iron core, such as that of the Earth. A large
molten iron core would generate a strong magnetic field. Thus, iron must have stayed mostly
on the outside layers of Mars, making the surface red with rust.
Recently, Mars Global Surveyor returned the first definitive measurement of a Martian
magnetic field. Therefore, if the core of Mars is large and composed of iron as the Mars
Pathfinder measurement shows, then this theory about the evolution of Mars may not be
completely correct.
This is a image of the Tharsis
Montes volcano region showing
Olympus Mons and a few other
volcanoes in red/yellow. Image
from: NASA
Martian Volcanoes
On this map of Mars, the lightly
cratered Tharsis Ridge is shown,
as well as the heavily cratered
Martian highlands (near the
bottom of the picture), and Valles Marineris to the right. The volcanoes are the yellow and red
dots in the sea of blue in this image.
The Tharsis Ridge is the home of several volcanoes, including Olympus Mons. Olympus
Mons is the leftmost volcano in the image. The three large volcanoes which accompany
Olympus Mons on the Tharsis Ridge are Arsia Mons, Pavonis Mons, and Ascraeus Mons.
Measurements returned by Mars Global surveyor demonstrate the very large size of these
volcanoes. Other volcanos named Tharsis Tholus, Ceraunius Tholus, Elysium Mons, and
Albov Tholus are found in the right-hand side of the large topographic map of Mars, as well as
the very large version of the map to the left. These volcanoes came into being early in
Martian history.
Martian Floods
Separate from the Martian outflow channels, or the river
valley networks, are large Martian lakes (600 km, or
~1000 miles across) which exhibit evidence of a
periodic and catastrophic release of water in the form of
floods. This evidence is found with an examination of
the shorelines surrounding the lakes.
An analysis of the combined evidence from the Martian
outflow channels, the river valley networks, and
catastrophic flooding suggests two possibilities for the
global Martian water cycle.
This is an image showing evidence of
Martian flooding. COURTESY OF NASA
The Composition of Jupiter's Interior
The composition of Jupiter's interior is mostly the simple
molecules hydrogen, in the form of liquid.
Under the cloud layers, when the pressure of the interior
becomes high enough, the hydrogen of which Jupiter is made
changes to liquid hydrogen, which gradually changes further
to liquid metallic hydrogen.
The core of Jupiter is made out of heavier, rocky and metal
elements.
The Structure of Jupiter's Interior
There is no surface to the giant planets, only a gradual change
from the atmosphere, as shown in this drawing.
The gases which Jupiter is mostly made of change to liquid inside Jupiter, but the change is
very gradual. Therefore the giant planets do not have strict layers, as the earth-like planets
do.
The liquid sections of
Jupiter form by far the
largest portions of the
planet, and penetrate
very deep into the
planet. The first liquid
layer inside Jupiter,
immediately under the
atmosphere, is the liquid
hydrogen layer. Under
the liquid hydrogen layer
is a liquid metallic
hydrogen layer.
At the deepest part of
Jupiter is the core, which
is probably the size of
planet Earth.
Jupiter's Moons and Rings
Jupiter has 63 moons and a ring system. The four Galilean satellites; Io, Europa, Ganymede,
and Callisto, are among the most interesting of all solar system bodies, particularly Io, with its
active volcanism, and Europa with the possibility of a water environment friendly to life. The
Galileo spacecraft explored the moons while orbiting Jupiter for eight years: 1996-2003.
Other moons, in order of their distance from Jupiter, are: Metis, Adrastea, Amalthea, Thebe,
Themisto, S/2003 J6, S/2003 J1, Leda, Himalia, Lysithea, Elara, S/2000 J11, S/2003 J20,
S/2003 J3, S/2003 J12, S/2001 J10, S/2003 J18, S/2003 J16, S/2001 J7, Harpalyke,
Praxidike, S/2001 J9, Ananke, S/2001 J3, Iocaste, S/2001 J2, S/2003 J15, S/2003 J17,
S/2003 J11, S/2003 J9, Carme, S/2003 J19, S/2001 J6, S/2002 J1, S/2001 J8, Chaldene,
Isonone, S/2001 J4, S/2003 J4, Erinome, Taygete, Pasiphae, S/2001 J11, Kalyke, Sinope,
Magaclite, S/2003 J7, S/2001 J5, S/2003 J13, S/2003 J5, S/2001 J1, Callirrhoe, S/2003 J10,
S/2003 J8, S/2003 J14, and S/2003 J2. These moons are part of a class of moons called the
"Small Moons". Jupiter's moons are named after mythological figures.
The Rings of Jupiter
Jupiter has a series of rings circling it! Unlike Saturn's rings, which are clearly visible from
Earth even through small telescopes, Jupiter's rings are very difficult to see. So difficult, in
fact, that they weren't discovered until a few years ago. Jupiter's rings were first found by the
Voyager 1 spacecraft in 1979.
There are three parts to Jupiter's rings. The innermost, cloud-like ring is called the Halo Ring.
The next one out is the Main Ring, which is quite narrow and thin. Beyond the Main Ring is
the wispy, nearly transparent Gossamer Ring. As shown in the diagram, the Gossamer Ring
has two parts: the
Amalthea Gossamer Ring
(closer to Jupiter) and the
Thebe Gossamer Ring.
Saturn's rings are mostly
made of ice. Jupiter's
rings are different - they
are very dark and difficult
to see. They are made up
of small bits of dust. The
Galileo spacecraft helped
us discover where that
dust comes from. Meteors
striking the surface of
Jupiter's small, inner
moons kick up dust which
then goes into orbit
around Jupiter, forming
the rings.
An Overview of Jupiter's Atmosphere
The king of planets is aptly named because it not only has the most dymanic atmospheric
motion, but also the most riveting cloud patterns and storms, and the most majestic
appearance of the giant planets.
The dramatic appearance of Jupiter stems partially because the composition of Jupiter's
atmosphere includes complicated molecules such as ammonia and methane, as well as
simple molecules such as helium, hydrogen, and sulfur. The composition also includes exotic
molecules such as germain.
The atmosphere of Jupiter is only a narrow surface layer, compared to the vast interior of the
planet. The three clouddecks of Jupiter are to be found at different levels in the troposphere,
while hazes of smog can be found higher in the atmosphere.
Jupiter is not much changed from its early evolution out of the early solar nebula, and in fact,
may still be forming!
This is a three-color filter image of Jupiter
and Io. It was taken on June 10, 1979 by
Voyager 2. Dr. Micheal Belton
An Overview of Jupiter's
Atmospheric Composition
Jupiter's atmosphere is mostly made of
the simple molecules hydrogen and
helium.
Sulfur is present there, as well as nitrogen
and oxygen. Nitrogen and oxygen make
up the air that we breath every day on
Earth.
These molecules combine to make clouds
of complex molecules, such as clouds of
water and smog.
A Look at Jupiter's Clouds
Jupiter shows a pattern of clouds of white, brown, and orange. And then there is the Great
Red Spot. The Great Red Spot is the largest of the clouds of Jupiter. Other cloud shapes
include eddy shapes, white ovals, brown ovals, and brown barges. The eddies and white
ovals are outlined in this picture, when shown at full size.
These clouds form in stripes and move across the face of Jupiter. The stripes are similar to
those found on all the giant planets.
There are three layers of clouds on Jupiter, and each one is composed of different molecules.
At one level there are clouds of ammonia, at another level there are clouds made of ammonia
and sulfur, and at a third level there are clouds of water (H2O).
Hazes of smog on Jupiter are to be found at very high altitudes above the clouds of Jupiter.
The Structure of
Saturn's Interior
There is no surface to the giant
planets, only a gradual change
from the atmosphere, as
shown in this drawing.
The gases which Saturn is
mostly made of change to
liquid inside Saturn, but the
change is very gradual.
Therefore the giant planets do
not have strict layers, as the
earth-like planets do.
The liquid sections of Saturn form by far the largest portions of the planet, and penetrate very
deep into the planet. The first liquid layer inside Saturn, immediately under the atmosphere, is
the liquid hydrogen layer. Under the liquid hydrogen layer is a liquid metallic hydrogen layer.
At the far interior is the core of Saturn.
Motions in the interior of Saturn contribute in a very special way to the development of the
powerful and extensive magnetosphere of Saturn. Heat generated within Saturn contributes
to the unusual motions of the atmosphere
The Composition of Saturn's Interior
Saturn's composition is primarily that of simple
molecules such as hydrogen and helium, but there is
also ice of ammonia, ice of methane and water ice.
Under the cloud layers, when the pressure of the
interior becomes high enough, the hydrogen of which
Saturn is made changes to liquid hydrogen, which
gradually changes further to liquid metallic hydrogen.
Compared to Jupiter, Saturn does not have as much
metallic hydrogen, but there is more ice. Because the
magnetosphere comes from the metallic layer, this
means that Saturn has a smaller magnetosphere than
does Jupiter.
At the far interior of Saturn is found the core, which is
made of rocky and metal elements.
An Overview of Saturn's
Atmosphere
The dramatic appearance of Saturn stems mainly
from the spectacular rings. The atmosphere looks
much less dramatic. The clouds of Saturn are
much less colorful than those of Jupiter. This is
because the composition of Saturn's atmosphere
includes more sulfur. This adds to Saturn's
overall yellow appearance. When you look
closely, however, Saturn's atmosphere is just as
fierce as that of Jupiter!
The atmosphere of Saturn, like Jupiter, is only a
narrow region, compared to the vast interior of
Saturn. The three clouddecks of Saturn are to be found mostly low in the atmosphere, while
hazes of smog can be found higher up.
Saturn is not much changed from its early evolution out of the primitive solar nebula, and in
fact, may still be forming!
Motions in the cloud patterns indicate that, like Jupiter, the basic weather of Saturn can be
described as a striped
Saturn Clouds, overview
This image of Saturn makes use of false color to show the cloud pattern. The clouds form in
bands which move across the disk of Saturn. The banded pattern of clouds, or stripes, is
similar to those found on all the giant planets, particularly in Jupiter's belts and zones. The
similarity among all the giant planets, even Uranus, suggests that there may be a common
way this pattern is created.
Cloud shapes of Saturn include eddy shapes, white ovals, and brown ovals, just like on
Jupiter. A row of swirling eddies can be seen in the very middle of this image in white.
There are three clouddecks on Saturn, and each one is composed of different molecules.
There is a clouddeck of ammonia clouds, a clouddeck of ammonia hydrosulfide clouds, and a
clouddeck of water clouds (H2O).
Hazes of smog on Saturn are to be found at very high altitudes above the clouds of Saturn.
Saturn's Moons and Rings
The gas giant planet Saturn has a large group of 62 moons. Saturn's moon Titan is one of the
few moons in the Solar System with much of an atmosphere. It is also one of the largest
moons in the Solar System.
Some of Saturn's moons are odd. A giant crater on Mimas makes it look like the "Death Star"
from the Star Wars movies. Iapetus is quite dark on one side and very bright on the other.
Hyperion is shaped like a garbage can. Prometheus and Pandora are called the "shepherd
moons" because they herd particles into Saturn's "F ring". Phoebe is very dark and moves in
a strange orbit. It may be an asteroid or Kuiper Belt Object that Saturn's strong gravity
captured long ago.
The other medium-sized moons of Saturn are Rhea, Dione, Tethys, Enceladus, Janus and
Epimetheus.
Some of Saturn's moons are icy moons. Most of the others are small moons which are
basically large rocks in space. Some stories from old myths include characters that some of
Saturn's moons were named after.
This is a color image of Saturn's satellite Rhea
taken by Voyager 1 on November 12, 1980.
NASA/JPL
Saturn's Rings
Many people like Saturn's rings. Although Saturn isn't the only planet with rings, it is the only
planet famous for them. Almost every image or drawing of the planet has the rings included.
But few people know much about them or why they are there.
Saturn's rings are made mostly of ice and rock pieces. It looks like one big band, but is
actually many smaller bands combined. The particles range in size from a couple centimeters
to over a kilometer in size.
The rings are very thin. Although they reach diameters in the hundred thousands kilometers,
they are no more than 1.5 km thick. So how can such a thin layer of ice pieces be so
beautiful? The ice creates a rainbow effect much like a sprinkler does in the sun. The Sun's
rays are refracted by the frozen water, giving us a colorful display!
An gigantic new "ring" was discovered in 2009. The Phoebe Ring is about 100 times bigger
than the main ring system. Scientists think the ice and dust in the ring comes from the strange
moon Phoebe. Particles from this ring might cause the strange coloration of the surface of
Iapetus.
This image of Saturn and its rings was taken by Voyager 1 in 1980. Courtesy of NASA
An Overview of Uranus' Interior
The Giant planets do not have the same layered
structure that the earthlike planets do. Their
evolution was quite different than that of the
earthlike planets, and they have much more gas
and ice inside.
Uranus's interior is primarily made of methane ice.
Motions in the interior of Uranus help form the
magnetosphere of Uranus. Heat generated within
Uranus helps form the unusual winds of the
atmosphere.
This is a diagram of the interior of Uranus.
Image from: The New Solar System
The Structure of Uranus' Interior
There is no surface to the giant planets, only a gradual change from the atmosphere, as
shown in this drawing. Therefore the giant planets do not have strict layers, as the earth-like
planets do.
Ice begins forming in the atmosphere of Uranus and keeps increasing until there is slush, and
then solid ice. There is not much difference between the atmosphere and the ocean on
Uranus, unlike the earth, where there is a definite surface between the air and the ocean.
An Overview of Uranus' Atmosphere
The plain aquamarine face of Uranus confirms the fact that Uranus is covered with clouds.
The sameness of the planet's appearance shows that the planet's atmosphere is mostly
composed of one thing, methane. The planet appears to be blue-green because the methane
gas of the atmosphere traps red light and does
not allow that color to escape. Beside clouds of
methane crystals low in the atmosphere, smog,
composed of ethane (the same product that can
provide fuel for automobiles), is also present
high in the atmosphere. The cloud particles
constantly recycle themselves, first creating
then destroying the heaviest crystals. This is an
indication that Uranus' atmosphere is still
evolving from its formation out of the solar
nebula. Because Uranus lies on its side, Uranus
has very strange seasons. Motions in the cloud
patterns indicate that, like Jupiter and Saturn,
the basic weather of Uranus can be described
as a striped pattern of winds. This means that,
even though the pattern is hard to see, Uranus
is striped, just like Jupiter and Saturn.
Uranus Clouds, Overview
The clouds of Uranus, composed of methane crystals, are found very low in the atmosphere,
and are difficult to see below the smog haze s of the planet. False color is used, in the image
of Uranus to the right, to better show the pattern the clouds make. In the image, the
atmosphere displays a pattern of concentric circles (that is circles inside of circles). This is
because the center o f the image is the north pole. The winds of Uranus blow clouds
counterclockwise in the picture, as opposed to left to right as they would in an image of
Jupiter.
Because Uranus lies on its side, with the north pole facing the sun, the seasons, and weather
of Uranus should be very strange.
These are two images of
Uranus. The one on the left is
true image and the one on the
right is a false image.
a
Uranus' Moons and Rings
Uranus has 27 fascinating moons and a complicated ring system. The ring is a completely
different form of ring than the one around Saturn or Jupiter. At Uranus there is a very obvious
partial ring, or "ring arc".
Many moons are icy moons with fascinating surface features. These icy moons have no
atmosphere nor magnetosphere. The interiors of these moons are not active, and there is not
much possibility for life.
The moons are, in order; Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia,
Rosalind, Belinda, and Puck. These moons are part of a group called the "Small Moons". Icy
moons of Uranus are; Miranda, Ariel, Umbriel, Titania, Oberon, Caliban, and Sycorax. In
1999, four more Uranian moons were found. They include Prospero, Setebos, Stephano and
1986 U 10.
Moons of Uranus from left to right: Miranda, Puck, and Titana.
Icy Moon
Icy moons are large or small moons which are mostly made of ice. These moons are unlike
the earth's moon, which is made of silicate rock.
Perfect examples of icy moons are 3 of the Galilean satellites, Europa, Ganymede, and
Callisto. Except maybe for Europa and Triton, these moons have no atmosphere.
But the surfaces of these moons, especially Ganymede, show that in their history, something
may have happened inside which changed the way the surface of the moon looks today.
Activity in the interior could also provide an environment suitable for life.
An Overview of Neptune's Interior
The Giant planets do not have the same kind of layers inside that the Earth-like planets do.
Their evolution was quite different than that of the Earth-like planets, and they have much
more gas and ice inside.
Neptune's interior make-up is primarily methane ice, just as Uranus' is.
Motions in the interior of Neptune help form the magnetosphere of Neptune. Heat generated
within Neptune helps form the unusual winds of the atmosphere.
The Structure of Neptune's Interior
There is no surface to the giant planets, only a gradual change from the atmosphere, as
pictured in this drawing. Therefore the giant planets do not have strict layers, as the earth-like
planets do.
Ice begins forming in the atmosphere of Neptune and keeps increasing until there is slush,
and then solid ice. There is not much difference between the atmosphere and the ocean,
unlike the earth, where there is a surface.
An Overview of Neptune's Atmosphere
Neptune's atmosphere shows a striped pattern of clouds. This cloud pattern is very similar to
that of Jupiter and Saturn. Neptune even has a Great Dark Spot similar to Jupiter's Great Red
Spot.
The history of Neptune's atmosphere is similar to that of the other Giant planets. The
composition of Neptune clouds is thought to be methane molecules.
Motions in the cloud patterns give clues about Neptune's weather, which is similar to that of
Jupiter and Saturn.
Neptune's Great Dark Spot of
1989
Unlike Jupiter's Great Red Spot, the Great
Dark Spot of Neptune is thought to be a
hole, similar to the hole in the ozone layer
Earth, in the methane cloud deck of
Neptune. The white clouds shown in the
picture are above the "hole". In many
images of Neptune, the Great Dark Spot
can be seen to change size and shape.
on
This is a close-up view of the Great Dark Spot taken on the
Voyager in August 1989. NASA
Neptune's Moons and Rings
Neptune has 13 moons. It also has rings, but its rings are different from Saturn's.
Neptune's largest moon is named Triton. Triton is much larger than any of the planet's other
moons. Triton is a very cold place, so the moon is covered with ice. Even though Triton is cold
there is a lot going on there. It has geysers like the ones at Yellowstone Park on Earth. The
geysers shoot ice 8 km (5 miles) high into Triton's thin atmosphere! There may be water
under the ice at Triton. It is even possible that there might be life in that water. The interior of
Triton is probably geologically active.
The rest of Neptune's moons are much smaller than Triton. Nereid was discovered by Gerard
Kuiper in 1949. Despina, Galatea, Larissa, Naiad, Proteus and Thalassa were found by the
Voyager 2 spacecraft in 1989. Five more small moons have been found recently. Three of
those were discovered in 2002 and two more were found in 2003. The newest moons don't
have official names yet.
Neptune's rings are much darker than
Saturn's bright rings. Saturn's rings are
made of ice, which reflects lots of light.
Neptune's rings are probably made of
rocks and dust. Rocks and dust don't
reflect as much light.
This is a color image of Triton taken by
Voyager 2 in August 1989. Triton is
Neptune's largest satellite.
Surface Structures
Internal Structures
Atmosphere
Moons and Ring Systems