Have you ever wondered what the centre of
the Earth looks like? What would the centre
of other planets looks like. Today we are
going to explore this hidden realm in this
video. The 
planetary core consists of the innermost layers
of a planet. They can be entirely solid or
entirely liquid or maybe a mixture of both
solid and liquid layers as, in the Earth’s
case. The size of different cores in our solar
system varies. They can be about 20% to 85%
of a planets radius.
Gas giants are also believed to have cores,
though having cores much smaller than those
of terrestrial planet, but some have a core
larger than Earth. Jupiter has one 10-30 times
heavier than Earth. All terrestrial planetary
bodies (Earth, Venus, Mars, Mercury, and Moon)
have similar inner structures and consist
essentially of iron cores and silicate shells.
Based on geological and petrological data
available, they evolved during a similar scenario,
as evidenced by existence of crucial turning
point at the mid-stages of evolution of their
tectonomagmatic processes, associated with
the involvement of new geochemical-enriched
material in geodynamic processes. However,
according to paleomagnetic data, the magnetic
field on Earth existed about 3.45 Ga. Because
a new substance began to take part in tectonomagmatic
processes much later, it is considered that
liquid iron, responsible for the magnetic
field in Paleoarchean, was derived from chondrite
material of the primary mantle. This iron,
in the form of a heavy eutectic Fe + FeS liquid,
flowed down and accumulated on the surface
of the still-solid primordial core, generating
a magnetic field, but did not participate
in the geodynamic processes. Only melting
of the primordial iron core, which occurred
already in the middle of Paleoproterozoic,
led to a dramatic change in the development
of our planet. Very likely other terrestrial
planetary bodies—the Moon, Venus, and Mars—were
developed following the same scenario; the
situation on the Mercury is unclear yet.
Before we talk about the cores of planets
of our solar system, don’t forget to like
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So lets take a closer took at each of them
one by one-
Mercury- Mercury’s outer core is composed
of liquid metal, and now scientists have found
that Mercury’s inner core is solid and nearly
the same size of Earth’s inner core. Its
core nearly fills 85% of the volume of the
planet. This large core is huge compared to
the other planets in our solar system. It
has a solid silicate crust and mantle overlying
a solid iron outer core layer, followed by
a deeper liquid core and a possible solid
inner core.Due to the molten core that is
powering the weak magnetic field of the planet,
its interior is still active. It has an observed
magnetic field . Only 1% as strong as Earth’s
and resembles Earth field in being roughly
dipolar and oriented along its axis of rotation.
Researches believe its field is produced in
much the same ways as earth’s field by magnetohydrodynamic
dynamo mechanism.
VENUS- Venus is much like Earth, in its size
and density as they both are made of similar
components. It probably has a metallic core,
a mantle, a mantle made up of dense rock and
a crust of less dense rock. Its core is primarily
composed of iron and nickel, in a similar
way like Earth, but its lower density also
indicates that it has some-what other elements
like sulphur. No intrinsic magnetic field
has been detected for Venus though, and so
there is no direct evidence of a metallic
core, like Earth. Calculations of Venus’s
internal structure suggest that the periphery of
the core lies a little more than 3,000 km
(1,860 miles) from the centre of the planet.
Above the crust lies Venus’s mantle, which
makes up most of its volume. Despite the
high surface temperatures, temperatures within
the mantle are likely similar to those in
Earth’s mantle. Similar to heat production
within Earth, heat within Venus is thought
to be generated by the decay of natural radioactive
materials and transported to the surface by
convection.
EARTH- More than 90% of Earth’s mass is
composed of silicon, oxygen, iron and magnesium,
elements that form the crystalline elements
known as silicates. The crust accounts for
only 0.4% of the Earth’s mass, and 0.1%
of the total iron present. The rest 80-85%
of the iron is contained in the Earths core.
The upper mantle generates most of the basaltic
magmas, at a depth of hundred kilometres.
The upper mantle, which is rich in the olivine, pyroxene,
and silicate perovskite minerals, shows significant
lateral differences in composition. The lower
mantle is present at a depth of about 650
km to 2900 km mainly composed of iron and
magnesium bearing silicates. The mantle is
not static but churns in convective motions.
The Earths core is about the size of 3600
km, nearly the size of planet Mars, accounting
for about 1/3rd of the Earth’s mass. It
is mainly made of liquid iron alloyed with
nickel and other lighter elements. We are
sure about its liquid nature because of shear-type
seismic waves which are unable to penetrate
the core. A small central part of the core,
at a depth of 5100 km is solid iron. The inner
core is divide in two layers, this is known
by the polarity difference of iron within
them. Iron crystals in the innermost layer
are oriented in east-west direction, and the
orientation of the outermost layer is North
and south direction. Temperatures are extreme
ranging from 4000K-5000K at the outer core
and about 5000-7000K in the inner core. About
1/5th of the heat that flows to the surface
is from the core’s reservoir. Helical fluid
motions in Earth’s electrically conducting
liquid outer core have an electromagnetic
dynamo effect, giving rise to the geomagnetic
field. The planet’s sizable, hot core, along
with its rapid spin, probably accounts for
the exceptional strength of the magnetic field
of Earth compared with those of the other
terrestrial planets
MARS- Not much is known about the interior
of Mars. Its central core has a radius of
about 1200 km- collected from isotope 2000
km, as indicated by its moment of inertia.
Data collected from isotopic meteorites that
the planet separated- into a metal rich core
and a rocky mantle 4.5 billion years ago.
It possibly contained core-generated magnetic
field in the past, which might have stopped
within 0.5 billion years of its formation.
Its core might me more sulphur rich and the
mantle might be more iron-rich as suggested
my the meteorites. Mars is almost certainly
volcanically active today, although at a very
low level. Some Martian meteorites, which
are all volcanic rocks, show ages as young
as a few hundred million years, and some volcanic
surfaces on the planet are so sparsely cratered
that they must be only tens of millions of
years old.
JUPITER- The atmosphere of Jupiter only makes
ups a small fraction of the entire planet.
No direct observations of the Jupiter’s
core has been made and its hard to draw conclusions.
But from observed quantities like temperature,
pressure , mass , shape, radius, rate of rotation
etc. , theoretical descriptions and models
have been proposed. The centre temperature
is estimated to be around 25,000 K, consisted
with the internal source of heat inside Jupiter
which allows it to radiate twice as much energy
as it receives from the sun. The pressure
at the centre ranges from 60-100 million atmospheres.
Under such enormous pressure, it is believed
that hydrogen might be present in metallic
state. It is made up of about 70% of hydrogen
and 24% helium. astronomers have concluded
that some helium that was dissolved in the
fluid hydrogen in the planet’s interior
has precipitated out of solution and sunk
toward the planet’s centre, leaving the
atmosphere depleted of this gas. The precipitation
is constant as the planet is gradually cooling
down. It is evident from the recent models
that transition from molecular to metallic
hydrogen occurs at 1/4th of the distance down
towards Jupiters centre. No solid surface
exist in any of these models. Most models
include a dense core with a radius of 0.03–0.1
that of Jupiter. Although there is not much
information about the source of internal heat.
The most favoured explanation invokes a combination
of the gradual release of primordial heat
left from the planet’s formation and the
liberation of thermal energy from the precipitation
of droplets of helium in the planet’s deep
interior. It has one of the most strongest
observed magnetic field in the solar system,
generated in its core.
SATURN- Saturn has a low mean density which
is provides and evidence that most of its
composition is mainly hydrogen. Under the
extreme pressure above one kilobar and extreme
conditions, hydrogen is usually present as
a liquid. More information is obtained about
the interior structure of Saturn from studying
its gravitational field, which is not spherically
symmetrical. The fluid molecular hydrogen
which is present at a of distance about halfway
between Saturn’s cloud tops and its centre,
undergoes a major phase transition to a fluid
metallic state at roughly 2 megabits and temperature
of about 2000 K. This fluid metallic state
resembles a molten alkali metal such as lithium.
A rock and ice mister that is of about 15-18
Earth like masses is believed to present at
the central core. Saturn’s magnetic filed
is essentially produced in the same way as
that of Earth’s. A very striking change
was observed in the last 25 years. The magnetic
field lines of Saturn are made more symmetrical
to the rotational axis before they reach the
surface by their passing through a non-convecting,
electrically conducting region that is rotating
with respect to the field lines. This led
to a conclusion that this might be related
to the action of deep electric currents involving
the conducting core. Saturn’s core could
have originated with 10-20 Each like masses
built up from the accretion of ice-rich planetesimals,
as suggested by the calculation made from
thermal evolution. a large amount of gaseous
hydrogen and helium from the original solar
nebula would have accumulated by gravitational
collapse. It is thought that Jupiter underwent
a similar process of origin but that it captured
an even greater amount of gas.
URANUS- Uranus has a higher proportion of
elements heavier than hydrogen and helium.
It has a density lower than Jupiter. Different
ratios of silicates and metals, water, methane
ammonia and gasses are proposed by different
models. Uranus is shown as a fluid planet
with gaseous higher atmosphere. The pressure
at the centre is about 5 Megabars. Scientists
have obtained more information about the interior
by comparing a given model’s response to
centrifugal forces, which arise from the planet’s
rotation, with the response of the actual
planet measured by Voyager 2. This response
is expressed in terms of the planet’s oblateness.
By measuring the degree of flattening at the
poles and relating it to the speed of rotation,
scientists can infer the density distribution
inside the planet. For two planets with the
same mass and bulk density, the planet with
more of its mass concentrated close to the
centre would be less flattened by rotation.
Before the Voyager mission, it was difficult
to choose between models in which the three
components—rock, ice, and gas—were separated
into distinct layers and those in which the
ice and gas were well mixed. From the combination
of large oblateness and comparatively slow
rotation for Uranus measured by Voyager, it
appears that the ice and gas are well mixed
and a rocky core is small or nonexistent.
NEPTUNE- Neptune has a mean density less than
30 percent of Earth’s and is the densest
among the gas giants. A larger percentage
of Neptune’s interior is made up of molten
rock materials and melted ice. Data from the
Voyager 2 suggests that that Neptune is unlikely
to have a distinct inner core of molten rocky
materials surrounded by an outer core of melted
ices of methane, ammonia and water. Heavier
exempts and compounds might me spread uniformly
throughout the interior, rather than being
condensed at the centre. The large fraction
of Neptune’s total heat budget derived from
the planet’s interior may not necessarily
imply that Neptune is hotter at its centre
the Uranus.
Though not much is known about about the Jovian
planets, we have tried our best to provide
you with valuable information about them.
What do you think about these extreme centres?
Can we know more about these beautiful planets?
Let us know what you think in the comment
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