The density of Earth\'s core may seem difficult to imagine given that the steel

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The density of Earth's core may seem difficult to imagine given that the steel bearings we used have a density much lower than the estimated density of core materials. However, there are common substances that have densities that equal or exceed these values, even at Earth's surface. Lead, at 11.35 g/cm^3, and mercury at 13.55 g/cm^3, have densities which straddle the range given for core materials. The pendulum weights used in Part C are made of the very hard alloy tungsten Carbide, density 15.8 g/cm^3. (Gold, bu the way, while not as common as lead or mercury, has a density approaching twice that of lead, 19.32 g/cm^3.) One theory of planetary is that immiscible materials differentiate - that is, denser matter sinks toward the center of a planet and lighter matter to the surface. How do your observations from this lab relate to this theory? The density (at standard temperatures and pressures) of some planet-forming substances are: Iron: 7.87 g/cm^2 Basalt: 3.0 - 3.3 g/cm^3 Water 1.00 g/cm^3 Ice: 0.92 g/cm^2 "Cold ices" of carbon dioxide, methane, ammonia, and hydrogen: 0.07 - 0.09 g/cm^3 The inner planets (Mercury, Venus, Earth, and Mars), also called the "terrestrial" planets, have thick mantles of rock surrounding dense iron-nickel cores. In general, the greater the density of the planet, the greater the relative size of the iron core, forth is the densest planet, followed by Mercury (5.43 g/cm^3), Venus (5.2 g/cm^3), and Mors (3.91 g/cm^3). Each have magnetic fields. Our moon has on average density of 3.34 g/cm^3 and has no magnetic field. What is the likely composition of the moon? A prevailing theory of the origin of the moon states that a very large body (roughly the size of Mars) collided with Earth, and that material was ejected into space where it coalesced to form the moon. Would you think that the moon formed before or after Earth's differentiation? Explain your answer.

Explanation / Answer

33.The denser materials sinks first and concentrate Fe-Ni alloys and denser oxides toward the center under the influence of gravitational force. The differentiation of earth is caused by a combination of factors like heating, gravitational collapse, impacts and concentrated radioactive heat.

Once melting began, mobility within the earth increased. Denser portions of the melts move downwards whereas lighter portions rose. There is generation of enough heat to melt the entire earth with the exception of outermost chilled layer. i.e. solid crust This layer may also have melted if the heat did not escape to the space.

34.a. Moon is a differentiated body. It has distinct core, mantle and crust. The inner core of the moon is a solid Fe- rich while its outer core is made up of molten iron. There is a partially molten boundary layer of radius of about 500 km around the core which develops due to fractional crystallisation of global magma ocean subsequently after the moon's formation about 4.5 billion years ago. The first minerals to formed from the crystallisation of this global magma ocean were Fe and Mg silicates olivine and pyroxene.

After 75% crystallisation completed less dense minerals like anorthositic plagioclase feldspar crystallised and floated and forms anorthositic crust of about 50 km thickness. After that most of the magma ocean crystallised quickly leaving behind the KREEP rich magmas which contains incompatible and heat producing elements and remained partially molten for several million years

b. The moon was formed shortly after the earth's formation. It was formed out of the debris left by the collision of earth and a Mars like planetary body approximately about 4.5 billion years ago.

There were evidences that moon was formed after the earth's formation:

Since moon has a relatively small iron core and a lower density than the earth

The orientation of earth's spin and moon's orbit have similar orientation

stable isotope ratio of moon rocks has a similar composition as terrestrial rocks

Due to the collision and the heat generated in the impact the moon once had a molten surface

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