jupiter's volcanic moon io

8/6/2019 Jupiter's Volcanic Moon IO

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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.


29/32

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.


30/32

Decker,Robert and Barbara,VOLCANOES, 3rd Edition,W.H.Freeman and Co.,New

York,NY,1998.

Comins, Neil and Kaufmann III,William, DISCOVERINGTHE UNIVERSE, 5thEdition,W.H. Freeman and Company, NewYork, 2000.

Fix, John D.,ASTRONOMY, McGraw-Hill, Boston, MA, 1999.

Fuller, Sue, POCKETS: ROCKSAND MINERALS, DK Publishing Company, New

York,NY, 1995.

Nicholson, Iain,UNFOLDING OUR UNIVERSE, Cambridge University Press, New

York,NY, 1999.

Reader's Digest Pathfinders,EARTHQUAKES ANDVOLCANOES,Reader's Digest

Children's Publishing, Inc., Pleasantville,NY, 2000.

Rogers, John H,THE GIANT PLANET JUPITER, Cambridge University Press, New

York,NY, 1995.

Schreier, Carl,A FIELD GUIDETOYELLOWSTONE'S GEYSERS, HOT SPRINGS,

AND FUMAROLES,Homestead Publishing, Moose,Wyoming, 1999.

Seeds, Michael, FOUNDATIONS OF ASTRONOMY, 4th Edition,Wadsworth

Publishing Company, Belmont, CA, 1997.

References


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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

tectonic andvolcanicprocesses haveshapedthesurfacesof these worlds.

Rothery, DavidA., SATELLITES OF THE OUTER PLANETS, Oxford University Press,

NewYork,NY,1999.

Bibliography


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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.

jupiter's volcanic moon io

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