SOLAR SYSTEM

Detailed explanation-1: -As our planet became a molten mass, layers formed (Fig. 7.3). The densest material, containing iron and nickel, settled to the core in the center of the earth. Less dense matter, containing iron rich silicates-compounds of silicon and oxygen-formed the vast interior mantle.

Detailed explanation-2: -What makes the Earth habitable? It is the right distance from the Sun, it is protected from harmful solar radiation by its magnetic field, it is kept warm by an insulating atmosphere, and it has the right chemical ingredients for life, including water and carbon.

Detailed explanation-3: -After the solar nebula collapsed to form our Sun, a disk of material formed around the new star. The temperature across this protoplanetary disk was not uniform. Since different materials condense at different temperatures, our solar system formed different types of planets.

Detailed explanation-4: -The temperature of the early solar system explains why the inner planets are rocky and the outer ones are gaseous. As the gases coalesced to form a protosun, the temperature in the solar system rose. In the inner solar system temperatures were as high as 2000 K, while in the outer solar system it was as cool as 50 K.