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1. ABSTRACT
We/ve attempted to present the studies we conducted on some of the characteristic
features of Ganymede on areas of its terrain, core dynamics and internal mass, tenuous
atmosphere, magnetic field, and possibility of sub-surface oceans etc. collected from existing
studies and journals available from previous studies conducted by space missions like Galileo
and Voyager also presented along-with in each of these sections are possible scientific studies
we’ve proposed. Further in the report, impacts these studies could have on the scientific world
and humanity at large have been discussed and reason for selecting Ganymede leads to various
proofs and evidences which led us to propose various scientific studies.
2. INTRODUCTION
Ganymede (Jupiter III) is the largest and most massive moon of Jupiter, the third in
numerical order. Possessing a metallic core, it’s the only moon in the Solar System to have
magnetic field. It’s the seventh satellite outward from Jupiter, in a 1:2:4 orbital resonance with
two of the others – Europa and IO, and takes roughly a week to complete once around the orbit.
3. REASONS FOR SELECTION OF GANYMEDE
3.1. Ganymede’s core dynamics and internal
mass
• Ganymede was formed by homogenous accretion
of water ice and silicate particles (about 50% mass)
withabundance of radioactive elements like uranium,
thorium and potassium.
• The centrifugal rotation of circumplanetery disk
(CPD) interacting with energy forms like viscous heating,
accretion on to CPD,planetary irradiation and heating from
the ambient circumstellar nebula also aided the process.
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Three theories exist with strength for defining the formation of core and dynamics:
1)COMPOSITIONAL BUOYANCY
2)THERMAL EVOLUTION
3)ORBITAL THERMAL EVOLUTION
• Mass is the defining parameter of a moon. Mass distribution categorizes all other
properties of the Ganymede like magnetic field, density, gravitational influence etc. The
distribution of water-ice layer in Ganymede can also be observed easily by knowing the
mass distribution.
• Ganymede is the only moon having differentiated internal structure (according to earlier
studies of Galileo and Voyager) with metallic core, rock mantle, thick ice (water-ice in
that distribution).three layer distribution is a main attraction of Ganymede.
3.1.2 PROPOSED SCIENTIFIC STUDIES
• Accretion growth rate in CPD and its dependence with time is a mystery. It can only be
solved by finding Ganymede’s core mass distribution. This mission proposes an analysis
on Ganymede’smoment of inertia.
• Evolutional relationship between Ganymede and Callisto (dichtotamy) has always
interested planetary scientists. This mission also paves a path for analysing Callisto
through flybys.
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• Presence of elements like U, TH, and K is an attractive feature for Ganymede. With the
help of a particle analyzer, we can study the abundance and decaying of these radioactive
elements.
• On studying about Ganymede’s core and its mass, there is a possibility for obtaining
information about Super-Jovian moons (outside solar system). This mission ensures data
collection for further research on these moons.
• Density study of Ganymede and relationship between the volatile compounds (ammonia,
carbon dioxide) and the ice/freeze line is also a main objective of our mission.
3.2.1. Ganymede’s Intrinsic Magnetic Field
One of the great discoveries of NASA’s Galileo mission
was the presence of an intrinsically produced magnetic field at
Ganymede. Generation of the relatively strong (750 nT) field
likely requires dynamo action in Ganymede’s metallic core.
This was a very surprising find to planetary scientists because
in small objects like moons, it is generally thought that any
intrinsic field should have long since ceased to exist. Another
approach examined by scientists was “Compositional
Convection”, which is a different mechanism to explain how a
dynamo could operate. The question of how Ganymede could
possess a magnetic field is still a puzzle to scientists.
3.2.2. Proposed Scientific Studies:
Using a one-dimensional, three layer model of Ganymede, we find that magnetic field generation
can only occur if the sulfur mass fraction in Ganymede’s core is very low (<3%) or very high (>21%). Iron and other metals present on Ganymede would cool and condense to solid form at
the top of the core and then sink to the center. When the metals condense, latent heat is released
which can drive convection.
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But, this idea suffers from a significant problem that it happens at the bottom of the mantle,
which is much cooler than the core. This means that the heat generated by the process would be
absorbed by the mantle and so it is doubtful that this process could drive a dynamo for billions of
years.
Investigation of Ganymede can provide a brilliant insight into the production of intrinsic
magnetic field on it and solve the dilemma faced by planetary scientists worldwide.
3.3.1. Study of the moon’s aurora and presence of subsurface oceans
Identifying presence of liquid water is very crucial in determining the possibility of alien life and
further a possiblitity of colonising. Presence of a highly saline subsurface ocean beneath the icy crust has
been suspected due to the finds of Galileo Mission. Supporting these are the recent evidences from the
study of the auroral bands of Ganymede in UV by the Hubble telescope.
Ganymede is the only moon in Solar System known
to possess a magnetic field, propelled by a rotating liquid
iron core. Being close to Jupiter, it is also encompassed by
Jupiter’s stronger magnetic field. Jupiter’s rotation causes a
back and forth rocking of Ganymede’s aurora. Theory
predicts a wobbling of about 6 degrees around the poles.
This amount of rocking is inhibited to 2 degrees, believed to
be due to the counterbalancing effect of an electrically
conducting (highly saline, likely containing Magnesium
Sulphate) subsurface ocean.
The oceanic subsurface is believed to be 100km
thick, situated below a 150 km thick icy crust. It’s separated
into four layers of water between four layers of different
phases of ice with the pressure increasing with depth. The
top layer is Ice I – the low density ice that floats on surface
of water. The high pressure at bottom produces Ice VI that is
much denser, that it sinks in water. The water sorts into
layers based on it’s salinity with it’s salinity increasing with
depth. Highly saline water is the lowermost layer, just above the rocky seafloor.
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3.3.2. Proposed Scientific Studies:
• Due to high pressure and ice at the bottom, the possibility for hot-water vents to bring nutrients
into the ocean is low, a scenario under which extra-terrestrial life would occur. The resulting
water-rock interactions are also supportive of this by giving rise to formation of organic
molecules.
• Characterising its water body and icy crust by methods of spectrometry and employing
magnetometers to indirectly study these subsurface oceans by its effect on Ganymede’s magnetic
field can lead to great discoveries. UV spectrometric study in much closer proximity, compared to
HST could reveal more secrets of the moon’s magnificent aurora and magnetic fields.
• During the formation of ice layers between the oceans there exists possibility of air bubbles to get
trapped inside. Studying the morphological features of these air bubbles can give better insights
on the age of the moon and the period of formation of the ocean layers.
• Studying the salts of the oceans of Ganymede can give information about the salinity of the
water. This in turn can help in studying the temperature and climate changes of the moon.
3.4.1 Terrain Of Ganymede
As observed from the high resolution images obtained
from the probes such as Galileo and Voyager, the terrain of
Ganymede is divided between dark and white terrains. The white
region is composed of water ice (contaminated to some extend).
Dark regions are mostly craters. Ganymede is unique for its long
curved grooves in the crust .The densities of impact craters show
that the moon had several periods of crust formation.
3.4.2 Scientific possibilities
The crust of Ganymede is icy covered so the presence of stored gas content need to be studied as it can be
used as fuel for future space explorations. The possibilities of life on the moon is also a topic of research .
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3.5.1 Tenuous atmosphere
The tenuous atmosphere on Ganymede is mainly composed of oxygen. Its formation has been due
to the splitting up of ice water on its ice crust into hydrogen and oxygen molecules by interaction with
UVrays, thus hydrogen, being lighter, escapes into the space above and the oxygen tends to form the
atmospheric layer near the surface. Studies have also found ozone and few other gases entrapped in the
moon’s icy crust. Furthermore, the oxygen molecules are said to interact with the energetic particles in the
surface thus resulting in a glow mainly near the polar region. The studies have not been clear with what
the energetic particles in the atmosphere is, with few suggestions referring to it as a layer of ionosphere.
3.5.2 Studies Suggested
The studies on the oxygen layer formation has not suggested the escape of ozone from the icy crust, if the
formation of oxygen is from the icy crust like studies suggest, then the thickness of the crust will reduce
gradually letting the entrapped ozone and other gases out which could further create an atmosphere
similar to the earth’s atmosphere stopping further interactions with UV rays and ice crust.
The reason for the glow is also an interesting topic for further research.
4. Impacts On Scientific World And Humanity
• Understanding the Jovian system and unravelling its history, from its origin to the possible
emergence of habitable environments, will give us a better insight into how gas giant planets and
their satellites form and evolve. In addition, new light should be shed on the potential for the
emergence of life in exoplanetary systems.
• Ganymede provides a natural laboratory for analysis of the nature, evolution and potential
habitability of icy worlds in general,plays an important role within the system of Galilean
satellites, and has unique magnetic and plasma interactions with the surrounding Jovian
environment.
• The study of production of intrinsic magnetic field on Ganymede can enable scientists to
understand the origin of the field and how it interacts with Jupiter’s field.
• Surface and mineral mapping of Ganymede can give information on lithology, composition and
can also indicate the presence of minerals and other resources. The possibility of a potential fuel
can be thus investigated.
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• Water, in any form, is a key ingredient to any future home off world. Ganymede is protected by
two magnetic fields, one from its Jovian parent and the other hosted upon this moon which can
shield it from harmful foreign radiations.Thus, we can say that Ganymede may hold the key
towards providing a second home for hundreds of millions of individuals in the not so distant
future.
5. DISADVANTAGES OF THE MISSION
Ganymede’s terrain contains craters, grooves and ridges. This may affect the motion of the
lander. There exist a lot of impact craters on the dark terrain of the moon. This indicates chances
of further impacts which may damage the lander. The lighter terrain is tectonic is nature, which
is again a threat to the lander. Radiations due to the strong magnetic field of Jupiter can affect the
mission. The ocean layers are deep below the surface, under an icy crust of 130-150 km making
it difficult for direct observations and studies.
6. CONCLUSION
With all the available evidence and proofs, we have arrived at a conclusion that Ganymede is
the best Jovian moon for a rover mission. If data from the HST situated hundreds of millions of
kilometers from Ganymede could present so much positive ideas and models about the interior of
the solar system’s largest moon,we believe that a lander mission to this moon will definitely
make an impact on the scientific world and humani

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