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Submitted to: Submitted by:
Dr.V.S.CHAUHAN
Roll No.: 2k7/EC/700
Name: Sujeet Kumar
REPORT
ON
"IO(Jupiter'sVolcanic Moon)
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2009
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Introduction
Io Statistics
Tidal Heating
Volcanism On Io
Lava Lakes
Lava Flows
Lava Fountains
Tvashtar
Volcanic Plains
Plume Eruptions
Prometheus
Pele
Mountains
Jupiter's Magnetosphere
Io Atmosphere
Latest Discoveries
References
Bibliography
Table of Contents
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Interior of Io
This cutaway model illustrates the probable internal structure of Io.Based on gravity-
field measurements taken by the Galileo spacecraft during a close flyby of the moon,
scientists have determined that Io is differentiated.Differentiation is the gravitational
separationofmaterial in the interior of a planetor moonaccording todensity.While in
a molten state,dense materials such as iron will sink to the center of a planetary body
to form the core,and less dense elements such as silicon and oxygen will rise toward
thesurface.
Io is believed to have a dense core composed of iron and iron sulfide (shown in gray).
The radius of the core is approximately 900 km (560 miles) which extends about
halfway to the surface. It is likely that the core formed either from internal heating
processes during the early stagesof the moon's formation,or as a result of the ongoingtidal heating that drives the volcanic activity at the surface. Surrounding the core is a
mantle of partially molten rock (shown in yellow-orange), which is overlain by a
relatively thin,rock crust (shownin brown).
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Orbiting the giant planet Jupiter is the
fascinating moon, Io, one of four moons
discovered by Galileo in 1610.One look at Io
and it is obvious that something unusual is
goingon there.Its mottled surface is a collage
of colors-yellow, orange, red, and blackish
browns -
which make it look somewhat like a gigantic
pizza. The explanation for this remarkable
color palette is found down on the surface.
Volcanoes! Io is literally bursting with volcanic activity. Volcanoes spew out vastamounts of sulfurous material which cover Io's Iandscape. Io's surface coloration
reflects thevarious colors that sulfur takesonat different temperatures.
Fiery volcanoes pepper Io's landscape, and massive lava flows spread out over
enormous distances. From its surface, geyserlike eruptions eject dust and gas
hundreds of kilometers into space,which fall back to the ground in elegant umbrella-
shaped plumes. Some of the hottest temperatures in the solar system outside of the
sunare found here,andyet mostof the surface is bitterly cold.
Intense radiation from Jupiter's
atmosphere over the course of the
mission has severely damaged Galileo's
computer circuitry and has resulted in
failure of the spacecrafts computer
systems. In order to prevent the
possibilityof the
crippled spacecraft contaminating the environment of Io's neighboring moon,Europa,
which may harbor a liquid water ocean beneath its surface, the spacecraft will plunge
into the atmosphere of Jupiter on September 21, 2003. At that time, after a
tremendously successful eight year tour of the Jovian system,the Galileo mission will
cometoanend.
Introduction
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Io Statistics
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Tidal Heating
What force is responsible forpowering the volcanoes on Io? OnEarth, the heat source that produces
volcanic activity comes from energyrelea sed f rom the decay o f radioactive materials within theinterior, as well as from heat left overfrom Earth's formation. But Io is toosmall to have left over accretionalheat, and radioactive decay could notgenerate the tremendous energyrequired to power all of the volcanic
activity that exists on the moon.The answer is tidal heating.Tidal heating is the heatingof the interior of one planetary body caused by
stresses induced from the gravitational pull ofanother.
Jupiter is an enormous planet. More than 1300Earths would fit within its volume! As a result,
Jupiter exerts a tremendous gravitational force. Io,on the other hand, is a tiny moon which orbits veryclose to the giant planet. Io is therefore verystrongly affected by the pull of Jupiter's gravity.Thisimage taken recently by the Cassini Orbiter showsthe relativesizeof Jupiter and Io.
If Io were Jupiter's only moon, it would not be subject to internal stresses.But thereare other moons nearby which exert a gravitational pull of their own. Io's volcanicactivity is caused by the powerful force of Jupiter's gravity, coupled with thegravitational pull of Io's neighboring moons--Europa, Callisto, and Ganymede. Jupiterpulls Io inward toward itself, while the gravity of the outer moons pull it in the
opposite direction. These opposingforces cause the distance between Ioand Jupiter to vary, making Io's orbitslightly elliptical. As a result, Io issubjected to tremendous tidal forces
that alternately squeeze and stretchits interior.This causes Io's surface torise and fall by about 100 meters (300ft). (The highest ocean tides on Earthonly reach about 18 meters (60 ft)).This perpetual friction generatesenormous amounts of heat andpressure within Io, causing molten
material and gases torise through fractures in the crust and toerupt onto the surface.
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Volcanism on Io
Io is the most volcanically
active world in the solar
system.Most of its surface has
been sculpted by volcanic
processes generated deep
within its interior. Volcanic
eruptions were first observed
by the Voyager spacecraft in
1 9 79 , a nd h av e b ee n
witnessed in every flyby of the
spacecraft Galileo, which is
currently exploring the Jovian
system. Galileo recently detected more than 100 erupting volcanoes, and scientists
speculate that there may be as many as 300. In recent observations, some of the
smaller, fainter volcanoes appear to turn off and on,changing from hot and glowing to
cool and dim within a few weeks.Volcanic activity on Io is so relentless that there are
no signsof impact craters on its surface,because they are rapidly filled in with volcanic
material soon after they appear.Given the volcanicnatureof Io,it is not surprising that
place names on the moon are taken from various mythological associations with fire
and volcanoes.
The most distinctive features on Io are its volcaniccalderas, lava flows,and colorful deposits made by plume
eruptions.Io alsohasvast regions of volcanic flood plains.
Sulfur (S) and sulfur dioxide (SO ) are foundeverywhere
on Io, as evidenced by its surface coloration of yellow,
orange,red,and black.Thesecolorsrepresent the palette
of sulfur at varying temperatures. The patchwork of
white deposits is thought to be sulfur dioxide frost
which has condensed out on Io's cold surface.
New information about the role of sulfur in Io's volcanism has been obtained bycombining results from Galileo and Hubble SpaceTelescope observations. Sulfur gas
(S ), which is composed of pairs of sulfur atoms, was recently detected above Io's
volcano,Pele,by theHubble SpaceTelescope.This compound is stable at thevery high
temperatures inside the volcano,but once it is ejected and lands on the cold surface,
the sulfur atoms rearrange themselves into larger molecules of three or four atoms
(S and S ).These varieties of sulfur are red in color,and theyare the primary materials
thatmake up the red debris ring surrounding the Pele plume.
2
2
3 4
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The global extent of
sulfur on Io caused
c o n s i d e r a b l e
d e b a t e a s t o
w h e t h e r I o ' s
volcanic features
were produced by
m o l t e n r o c k
(silicate volcanism)
or molten sulfur.
T he a r g ume n t s
favoring s i l icatevolcanism were supported by the fact that the tall mountains and deep, steep-sided
calderas on Io require a material of considerable strength to support them.The issue
was finally resolved when Earth-based telescope detected temperatures at hot spots
ranging from 1000 K to1800 K.This is far too hot for sulfur to remain liquid,so silicate
magma has to be involved in these high temperature eruptions.But that does not rule
out the possibility that some of the lava flows on Io are composed primarily of sulfur.
In fact, the distribution of sulfur on Io is still a subject of some debate. It may be that
sulfur constitutes a relatively thin coating on Io's surface, or it could form relatively
thick deposits in localizedareas.
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Lava Lakes
Io's calderas tend to be larger than those found on Earth, but they display many other
similar features. They are roughly circular, deep, steep-sided, and many have dark
material on their floors, which is an indication that hot, fresh lava is present. Some of
the calderas appear to have a collapsed floor, as if the material supporting them had
drained away.
Some of the volcanic centers on Io are different in character from calderas found
elsewhere in the solar system.These are called patera.While they are volcanic in
origin,many of the patera have straight edges and sharp angles indicating they may be
related to fractures and movement in the crust.The image above is a mosaic of a
region covering about 850kilometers (509 miles) whereninepaterae canbe seen.
This image is of Chaac Patera, seen in
the lower left corner of the mosaic. It is
approximately 100 km (63 miles) long
and 30 km (19 miles) across.One of the
caldera walls in Chaac is about 2.8 km
(1.7 miles) high with a 70 degree slope.
This is about twice as high and steep as
the walls of the Grand Canyon. In the
southernmost area, several raised
plateaus and a deep, dark pit are visible. Similar features were seen during the 1959
eruption of the Kilauea volcano in Hawaii when a pond was formed as erupting lava
filled in a small volcanic crater.As the pond crusted over, lava drained back into the
ground leaving behind a perched plateau.The floor of Chaac patera has interwoven
domes and pitsmaking it virtually identical tocalderasonEarththaterupt fluid lavas.
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The three dark spots in this image of Io's
south polar region are volcanic calderas
that range from 10 to 20 km (6 to 13
miles) across.Thedark floorsare assumedto be recent lava flows, and the dark
material surrounding the calderas may be
material which was thrown out during
explosive eruptions.The yellow lava flow
at the southern edge of the image appears
to be connected to a caldera by a dark
channel. This lava flow is thought to be
composed of sulfur rather than silicate
materials.
This image of Zal Patera shows the edge of a
caldera (center top) which is marked by black
flows.The red areas are associated with places
where hot lava is erupting onto the surface.
The red material appears to follow the base of
a mountain, which may indicate that sulfurous
gases are escaping along a fault.
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Lava Flows
Io's volcanismdoes not produce steep-sided volcanic mountains.The volcanic lavas on
Io are very fluid, and form relatively low, gently-sloping mountains called shield
volcanoes.The lavas may either be silicate, sulfur, or a complex mixture of both .Thehighest temperature lavas are most likely silicate because sulfur cannot remain liquid
above its boiling point. The longest flows, however, may be composed primarily of
moltensulfur,which is very fluid.
This image shows Culann Patera,
which is one of the most colorful
volcanic centers on Io.The central
caldera has an irregular-shaped,
scallopedmarginanda greenfloor.
Lava flows are seen to spill out in
all directions from the caldera.
The dark, red curving line on the
northwest edge of the caldera
may be a crusted-over lava tube
feeding the nearby dark,hot flows
of silicate lava.
Most lava flows on Io are dark,but the
channelized lava flow in this image
emanating from Emakong is extremely
bright. Scientists speculate that this
lava flow is composed of sulfur rather
than silicate rock. Sulfur can be black,red,orange or yellow dependingon its
temperature. The serrated edges of
the flow indicate that it is highly fluid
andis
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working its way into every crevice over which it travels. New images show that thelava channel is roofed over in several places insulating the lava from the freezingtemperatures at thesurface andthis may allow the lava to travel longerdistances.
Lava flows extend for great distances on Io.The
longest, currently active lava flow in the solar
system is Amirani-Maui, which is more than 250
km (160 miles) long. The volcanic features
Amirani (right) and Maui (left, below center) at
first were thought to be two separate volcanoes.
This new Galileo image, however, shows thatMaui is actually an active lava flow that extends
west of the Amirani vent. Surrounding the
Amirani vent are plume deposits of sulfur-dioxide
snow which formed when gases expelled from
the vent,frozeand fell back to the surface.
Twelve different vents on Io erupt lava at temperatures greater than 2,200 degrees
Fahrenheit, and one may be as hot as 3,100 degrees Fahrenheit. Lavas of this
temperature have not been found on Earth for the last 2 billion years. Studying
volcanic processes on Io may, therefore, provide some insight into Earth's early
volcanic history.
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Lava Fountains
Lava fountains produce a spectacular show on Earth and they have also been observed on Io on the Tvashtar
region.In this image,a fissure eruptionejected moltenmaterial more than 1.5kilometers high (1 mile).Estimatesof
the temperature of the fountain range from 1,000 K (1,300 Fahrenheit) to 1,600 K (2,400 Fahrenheit). The
brightnessof thefountainoverloaded thecamera'sdetector andcausedit toshow upas a whiteblur in theimage.
The image also shows a the first close-up views of a large chain of calderas on Io.The calderas in this region
dwarf other calderas in the solar system with dimensions of 290 km by 100 km (180 miles by 60 miles).This
is larger than the largest caldera on Earth.
This color image is an interpretive drawing
by Galileo scientists which shows the same
area in the photo above.The bright streak is
a series of lava fountains. Lava flows are also
visible on the floors of the caldera. The
darkest flows arethe most recent.
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Tvashtar
In December 1999, the Galileo spacecraft detected a dynamic eruption atTvashtar
Catena, a chain of volcanic calderas located near Io's north pole.The image above
reveals a change in the location of hot lava over a period of a few months from late
1999 toearly 2000.
In the second image, the orange and white areas on the left side are places where hot
lava has recently erupted.The two small white spots are places where molten rock is
exposed at the surface near the edges of the lava flows.The long, yellow and orange
stream is more than 60 km long and is a cooling lava flow.The white color in the
picture indicates the hottest material in the lava flow,while orange reflects the cooler
temperatures.The dark deposits in the vicinity of the active flowswerenot seen in the
image taken in theNovember,1999 flyby.
This temperaturemapshows themany locationsof
hot spots clustered in theTvashtar region.The red
areas are the hottest with the highest
temperatures reaching about 277 degrees Celsius
(530 degrees Fahrenheit). These locations indicate
where new hot lavahas come tothe surface.
The Tvashtar region also reveals something about erosional
processes on Io. The caldera in the center of this image is
surrounded by a mesa which is about 1 km (0.6 miles) high.The
margins of the mesa appear to be scalloped, a feature which is
typical of a process onEarth calledsapping.Sappingoccurswhen
groundwater seeps through to the surface at the base of a cliff,
weakening theoverlying material andcausing it to collapse.Since
there is no water on Io,the fluid driving this process is assumed
to be liquid sulfur dioxide. As the sulfur dioxide reaches the
near vacuumof space at Io's surface,it vaporizes andblastsawaymaterial at thebase of thecliffs.
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Volcanic Plains
Although there are mountains and
volcanic features of considerable
height on Io, much of its surface is
covered by immense regions of
low-level, volcanic plains. Across
these plains, contrasting light and
dark areas are visible which may be
the result of lava flows of different
ages or compositions, or deposits
left by the condensation of gases.
The average surface temperature
on Io is a frigid -150degrees Celsius(-240 degrees Fahrenheit). With
the exception of the volcanic areas
where the temperature is too high,
muchof the surface is covered with sulfur dioxide frost.
The plains surrounding many of
the volcanic centers appear to
have a bumpy texture as seen in
this image,. Because the plains
are relatively old, it is believed
that the texture is created over
time, possibly the sublimation
(the change of a solid directly
into a vapor or gas) of sulfur
dioxide.
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Plume Eruptions
Among themost impressive sights in the solar systemare theumbrella-shaped plumes
that can be seen over many of Io's volcanic centers. Due to Io's low gravity and low
atmospheric pressure, dust and gas ejected from volcanic vents rise to great heightsbefore falling back to the surface. Plumes on Io range in height from about 60 km (38
miles) to more than 400 km (250 miles). If Old Faithful inYellowstone National Park
weretoerupt on Io,it wouldrise toan incredible height of 35km(22 miles).
When the plumes were first
discovered, planetary scientists
t hough t t h at t he y were
explosive volcanic eruptions
similar to those of Mt.St.Helenswhich erupted in Washington
State in 1980. They have now
d e te r m in e d t h at p l u me
eruptions are more closely
related to geysers on Earth.
Geysers are powered by the
change of superheated water to
steam as it nears Earth's surface.Since there is no water on Io,sulfur and sulfur dioxide
are thought tobe the fluidsthatpower the plumeeruptions.
Scientists have developed models of how
plume eruptions may form. One theory
suggests that liquid sulfur dioxide comes
in contact with
heated rock or magma at some depth beneath the surface of Io.This contact causes
the sulfurous material to become superheated and to rise rapidly. By the time it
emerges into the cold atmosphere, it has expanded,cooled,and the material become
a high velocity column ofcold gas and frost particles.When the plume material returns
to the ground, it produces a fallout deposit usually in the form of a circular or oval-
shaped ring.Since plume-like deposits are seen in manyplaces on Io where plumes are
notcurrently active,manyplume eruptionsare thought tobe short-lived.
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An enormous plume
eruption was detected
during the August, 2001
flyby from a previously
undiscovered volcano. This
new plume rose at least 500
kilometers (300 miles) from
the ground, 10% higher than
the previously recorded tallest eruption. Particles from the eruption detected by
Galileo's plasma science instrument were found to be snowflakes composed of
sulfur dioxide molecules. These particle impacts will provide researchers with
information regarding the temperature and speed of the gas in the plume.
Plume eruptions can also form when hot lava flows over an area covered by sulfur
dioxide snow.The frozen material vaporizes underneath the lava and erupts through
an channel in the flow. This type of plume has been observed at the Prometheus
volcano.
To keep the plumes erupting,a large and steady
supply of sulfur dioxide is necessary.This may
occur as a result of the recycling of surface
deposits of sulfur dioxide. Scientists speculate
that thick sulfur dioxide deposits may be
overrun by lava flows, and those deposits that
are not sublimated (converted instantaneously
from solid to gas) are buried beneath the flow.
The lava forms a cap over the sulfur dioxide
deposits, and subsequent lava flows bury the
deposits even deeper. After many repeated
flows, the sulfur dioxide reaches a depth at
which it becomes liquefied due to the high
pressure of overlying material. When an
underground intrusion of magma comes in contact with the deeply buried sulfur
dioxide deposit, some of it becomes superheated and converts to vapor.The pressure
from this vapor increases until a path to the surface is opened, resulting in a plume
eruption.Material ejected during the eruption returns to the surfaceand the recycling
process is repeated.
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Prometheus
Known as Io's "Old Faithful", the
Prometheus volcano has been active
during every observation of it since it
was first seen byVoyager 1 in 1979.The
Prometheus plume is 80 km (50 miles)
tall, and although its size and shape have
remained constant over the years, its
plume location has migrated about 85
km (53 miles) to the west. Its volcanic
field is similar to those of Hawaiian
volcanoes,but it is much larger and more
active. The bright, ring-shaped depositaround the volcano forms when sulfur dioxide, ejected during the plume eruption,
condenses into snow and falls back to the surface. Scientists have been especially
interested in determining whether the Prometheus plume is erupting from a vent at
the west end of the dark lava flow,or if it is being producedbyadvancing lava as it flows
overa surface rich in sulfur dioxide.New images havehelped toresolve this question.
A caldera, dark lava flows, and a strange,
lumpy surface covered with sulfur-rich
snow are seen in this recent image.
Originally it was thought that all of the dark
material comprised one, long lava flow.
However, close examination of this image
indicates that the northeast end of the dark
material is actually a lava-filled caldera.
Scientists now believe that this caldera and
hot spot are the source of the Prometheus
lava. Lava appears to be transported
westward for roughly 100 km(60 miles) through lava tubes,where it breaksout ontoa
surface rich in sulfur dioxide snow. The Prometheus plume is created by the
interaction between the hot lava and the snow.On the western rim of the caldera is
evidence that lava has spilled over the edge.This indicates that the caldera was,at least
once,completely filled with lava.Thehummocks located to theeast of thePrometheus
caldera are of particular interest. One theory regarding their formation is that they
resulted from supersonic volcanic blasts which plastered material onto preexisting
mounds onthe surface.
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The yellow areas in this infrared image are active volcanoes and lava flows, with the
Prometheus volcano located in the center. Prior to obtaining this high-resolution
image,only Prometheus and three other volcanoes had been observed to be active in
this area.In this image,however,14 active volcanoes havebeen detected.
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Pele
Io's most distinctive feature is unquestionably the volcanic center,Pele.Pele is the site of
an ongoing, high-velocity volcanic eruption. Deposits of sulfurous materials from Pele's
plume are ejected out to more than 600 km (375miles) from the vent.Its plume is nearly
invisible, except in back-lit photographs, and it is thought to be an example of a stealth
plume. Stealth plumes occur when the sulfur dioxide gas in the volcanic vent is at a very
high temperature.Upon being expelled from thevent,the gas rapidly expands resulting in
an undetectable,high-velocity jetof cold gas fromwhichnosnow is produced.
A dramatic display of how quickly volcanic activity can change the face of Io is shown in
these three images of the Pillan Patera region near Pele.The images showthe changes that
occurred betweenApril 1997 and July 1999.The image on the left was taken inApril 1997.
By September 1997 (center),a huge eruption occurred which produced a new dark spotthesize ofArizonaaround thevolcaniccenternamed PillanPatera.This eruption obscured
a portion of Pele's red ring. By July of 1999 (left), red sulfurous material had once again
begun tocover a portionof the darkmaterial aroundPillan,buthad not yet beenobscured
it.This may be an indication that both the Pele and the Pillan plumes were still active.
Another change in the 1999 image shows that a small volcano had erupted to the right of
Pillandepositing dark material surroundedby a yellow ring.
This is a temperature map ofthe Pele region imaged by the
i n f r a re d s p e c t ro m e t e r
o n bo a rd t h e G a l i l eo
spacecraft. Red indicates the
hottest lava flows,and purple
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represents coolerareas.Thehottest lava flowtemperatures recorded areapproximately
1400 K (2000Fahrenheit),which is similar to thetemperatures of basaltic flows found on
Hawaii'sKilauea volcano.
This image showsan outline of fresh,hot lava
that follows the margin of Pele's caldera.
Scientists believe that the Pele caldera is
filled with liquid lava and has a floating crust.
The lava lake appears to be confined to the
dark southern part of the caldera which
covers an area of about 15 km by 10 km (10
miles by 6 miles). Most of the lava lake is
covered by a cooler crust that floats on top
of the molten lava.The behavior of this lake
is similar to that of Hawaiian lava lakes,
although Pele's lake covers an area several
thousand times larger than the lava lakes in
Hawaii.
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Mountains
Not all mountains on Io are
volcanic in origin.About two
percent of the surface is
occupied by mountains
which have formed by other
processes, such as uplift and
thrust faulting. Some of
these mountains rise to
great heights , such as
Euboea Montes which is 13
km (8 miles) high. Their
sheer size and steepness provide further evidence that the material underlying themis rock and not some form of sulfur. Sulfur does not have the strength to support
mountains of this size. The lengths of the shadows cast by the mountains allow
scientists to estimate the their height.The mountain in the far right of this image has
beendetermined tobe approximately 8 km(5miles) inheight.
How these mountains form is not completely understood.One theory suggests that
crustal recycling is a possible cause. Io is continually being resurfaced by volcanic
activity at a rate of approximately 1 cm/year.At this rate, one kilometer of material is
being added to the surface every 100,000 years.The weight of this material places
tremendous strain on the crust, and may cause it to sink and merge with the molten
mantle.As a result of this compression, large crustal blocks may be forced upward
along deep faults. It is also possible that some of the mountains may have formed as a
result of intrusionsofmagma from deep within Io's interior.
Imagesof Euboea Montes (upper right) suggest
that it formed from the uplift of a large crustal
block. Close examination of images of the
mountain reveal that uplift caused a landslidewhich formed an enormous debris apron at its
base.The size of the debris flow is 200 km (125
miles) wide and contains an estimated 25,000
cubic km of rock.This landslide is 10,000 times
larger than the one that occurred during the Mt.St.Helens eruption in 1980.Only on
the flanksofOlympusMonsonMarshaveavalanches of this size beenobserved.
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Avalanches may also be responsiblefor the destruction of Ionianmountains. This recent Galileo
image shows a number of ridgesparallel to the margins of themountains.This provides evidencethat huge landslides are beinggenerated as the force of gravitycausesthemountains to collapse.
Telegonus Mensa was imaged by theGalileo spacecraft in October, 2001 forthe purpose of studying erosionalprocesses on Io.This image shows a cliffslumping on the edge of the mountain.
On Earth, wind and water are theprimary agents of erosion. Since Io hasneither water nor an atmosphere togeneratewinds,the slumping is dueto the the force of gravity.
The 240 km (150 mile) long mountain inthis colorized image provides informationabout the various types of materials thatmake up Io's mountains. The bright redmaterial is believed to be a compound ofsulfur that forms at very high temperatures.
The likely source of heat is molten rockmaterial.The yellow areas are other typesof sulfur compounds, and black indicatesfresh silicate lava.The green material tendsto form when sulfur lands on warm lava.The image reveals that the red material hasblown out of a long crack on the western
side of the mountain.Lava is seenemerging along the fault,and it defines the sideof themountain. Scientists speculate that rising plumes of hot material may be instrumentalin formingthese mountains.
This recent image may provideevidence of riftingon Io.In the centerofthe picture is a dark depression called Hi'iaka Patera.The northern andsouthern margins of Hi'iaka Patera have remarkably similar shapeswhich indicates they may have once fit together. Furthermore, themountains to the north and south look like they split and slid apart (by145 km (90 miles), forming a basin similar to DeathValley in California.Lateral movements such as this are caused by plate tectonics on Earth,but no evidence of a similar process on Io has yet been discovered.Scientists speculate that deep mantle plumes of rising masses of hotrock may be driving themovements.
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Jupiter's Magnetosphere
A magnetosphere is the region of space surrounding a planet which is dominated by
theplanet's magnetic field.Jupiter'smagnetosphere is enormous.In fact,it is the largest
structure in the solar system. It is molded into a teardrop shape by a stream of
energetic particles blowing away from the Sun called the solar wind.The side of the
magnetosphere facing the Sun extendsabout 3 million kilometers from the planet,and
its tail reaches out another 650million kilometers,to the orbit of Saturn and beyond.If
it were visible from Earth, it would appear several times larger in the sky than the full
moon.
Jupiter's magnetic field is generated deep within the planet. Although its outer
atmosphere is composed primarily of hydrogen gas, deep within the interior the
pressure is so great that the hydrogen becomes a liquid. Because of the tremendous
pressure,the electronsof thehydrogen atoms freely move from atom to atom,making
it a very good conductor of electricity. Because of this property, it is referred to as
liquid metallic hydrogen. Jupiter spins on its axis every 9.9 hours, generating
convection currents in the liquid metallic hydrogen.This produces Jupiter's powerful
magnetic field.
The Io plasma torus is located within Jupiter's magnetosphere and has considerable
impact on it. The torus is a ring of charged particles associated with the volcanic
activity on the moon.Radiation levels within the plasma torus are extreme and pose a
serious threatto spacecraft.
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This image taken on Jan. 4 and 5, 2001 by the Ion and Neutral Camera on NASA's
Cassini spacecraft,makes thehuge magnetosphere surrounding Jupiter visible in a way
never seen before.Jupiter's magnetic field has been sketched over the image.The disk
of Jupiter is shown by the black circle, and the approximate position of the Io plasma
torus is representedby theyellow circles.
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Io's Atmosphere
In spite of the large quantities of gas ejected by its many volcanoes,Io does not have a
significant atmosphere.Io's average surface temperature is so low,(about100 to 110K
(-280 to -290 degrees Fahrenheit),that much of the released gas condenses back ontothe surface as frost deposits. The thin atmosphere that does exist is composed
primarily of sulfurdioxidegas.
Some molecules of gas do
escape, however, and Io is
surrounded by a cloud of sodium,
potassium, and oxygen atoms.
The sodium cloud, visible in this
image, is the most easilyobserved. The source of the
sodium remains a mystery to
scientists because it has not yet been detected anywhere on Io's surface. Recently,
the element chlorine was also discovered. This finding leads scientists to believe
that sodium chloride, or common table salt, may exist on Io and influence its
violent volcanic activity. Prior to this discovery, only sulfur, oxygen, sodium, and
potassium atoms were observed escaping Io's atmosphere.
Two common compounds of chlorine are sodium chloride, table salt, and hydrogenchloride, which is a colorless gas emitted by volcanoes.Scientists do not yet know if
the chlorine is emitted from Io's volcanoes, or comes from the breakup salt on Io's
surface by charged particles in the plasma torus.How salt might form on Io is unclear.
It may be that there are subsurface rivers or aquifers supplying the fuel for Io's
volcanoes that carry dissolved salts, or the salts may be the result of chemical
reactions in theatmosphere.
W i t h i n J u p i t e r ' s
magnetosphere, there is a
significant amount of hot,
ionized gas, or plasma.This
plasma moves along with
Jupiter's rotating magnetic
field, sweeping charged
particles off the surfaces of
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This image of Io was taken while
the moon was in Jupiter's
shadow.The vivid colors are the
result of collisions between Io's
atmospheric gases and charged
particles trapped in Jupiter's
magnetic field. The red and
green colors are probably
produced by mechanisms similar to those that produce the aurora in Earth's polar
regions.The blue light indicates locations where dense plumes of volcanic vapor rise
into space.These may be placeswhere Io is electricallyconnectedto Jupiter.
As Io circles around Jupiter and
through the plasma torus , an
enormous electrical current flows
between them. Approximately 2
trillion watts of power is generated.
The current follows the magnetic field
lines to Jupiter's surface where it
creates l ightning in the upper
atmosphere.The first black and white
Hubble Space Telescope image (top)
shows the flux tube,where Io and Jupiter are linkedby an electrical current of charged
particles.Volcanic emissions from Io flow along Jupiter's magnetic field lines, through
Io, to Jupiter's north and south magnetic poles. In the second black and white image,
auroral emissions are visible at Jupiter's north and south poles.The ultraviolet image
below shows how the structure and appearance of Jupiter's aurora changes at it
rotates.
its moons as it passes them. Io has a particularly significant impact on Jupiter's
magnetosphere. Io's volcanoes continually expel an enormous amount of particles
into space, and these are swept up by Jupiter's magnetic field at a rate of 1,000 kg/sec.
This material becomes ionized in the magnetic field and forms a doughnut-shaped
track around Io's orbit calledthe IoPlasmaTorus.
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Latest Discoveries
Io Generates Noise, But No Magnetic Field
One of the mysteries about Io that scientistswerehoping to solve is whether ornot it
generates its own magnetic field.That question was put to rest with measurements
taken near Io's north and south poles during the August, 2001 flyby of the Galileo
spacecraft. The data revealed that no intrinsic field exists.This indicates that Io's
molten iron core does not have the same kind of convective activity that exists within
Earth's core. Convection in the core is responsible for generating Earth's magnetic
field.Io's core is assumed tobeheatedbythe tidal flexingof its surrounding layers.
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Schreier, Carl,A FIELD GUIDETOYELLOWSTONE'S GEYSERS, HOT SPRINGS,
AND FUMAROLES,Homestead Publishing, Moose,Wyoming, 1999.
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Earth'sDynamic Systems
The 8th edition of this highly acclaimed textbook on physical geology is now available.
The text focuses on the two major energy systems of the Earth: the plate tectonicsystem and the hydrological system. It is considered by many to be the best teaching
textavailable for introductory physical geology.
Hamblin,W.K.,THE EARTH'S DYNAMIC SYSTEMS.8th Edition,Prentice-Hall,Upper
Saddle River,NJ,1999.
Encyclopediaof theSolar System
A compilation of authoritative articles regarding recent findings in planetary science
research bymore than 50 eminent space scientists.
Weissman, P., McFadden, L., Johnson,T., Editors, ENCYCLOPEDIA OF THE SOLAR
SYSTEM,Academic Press,San Diego,CA,1999,Encyclopedia ofVolcanoes
A comprehensive reference work about terrestrial volcanoes and volcanic processes.
Includes discussions about volcanism on Io, Mars,Venus, and elsewhere in the solar
system.
Sigurdsson, Haraldur, ENCYCLOPEDIA OF VOLCANOES, Academic Press, San
Diego,CA,1999.
Foundations in Earth Science
An excellent introductory text in Earth science which includes the subjects of geology,
meteorology, oceanography, and astronomy. Topics are presented in nontechnical
language.Thetext is suitable foreveryone,including those with a limitedbackground in
science.
Lutgens, Frederick/Tarbuck, Edward, FOUNDATIONS OF EARTH SCIENCE,
Prentice-Hall,UpperSaddle River,NJ,1999.
New Solar System
This book provides a comprehensive guide to the solar system. It begins with an
overview of the solar system and follows with a discussion of each of the planets, their
primary features, and their satellites. Each chapter is beautifully illustrated and
contains up-to-date information regarding allof the topicscovered.
Beatty, J.K., Petersen, C.C., Chaikin, A., Editors, THE NEW SOLAR SYSTEM, Sky
Publishing Corporation,Cambridge,MA,1999.
Satellites of theOuterPlanets
This book is a geologic tour of 18 satellites of the outer planets.The author shows how
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ACKNOWLEDGEMENT
This report could not have been prepared, if notfor the help and encouragement from various
people. Hence, for the same reason I would like to
thank my teacher It was for his
support that I got proper guidelines for preparing
this report.There are many more people I would
like to thank; they are the peoples living in our
society, they helped me with the questions askedand the answers given by them were up to the mark,
theywere confident with their answers.
Mr.V.S.Chauhan.