Meteorites have been investigated by scientists over the past two centuries. the chemical elements they contain have been analyzed and what is most remarkable is that the chemical composition of chondritic meteorites is almost exactly the same as the chemical composition of the sun when gases like hydrogen and helium are not included in the comparison. their composition infers that they were made from the same original batch of material. the earth, which lies between the sun and the asteroid belt, the source of these meteorites, is believed to have been made from the same material as well. theory states that the sun and planets came into existence when part of an enormous cloud of gas and dust, drifting in the milky way galaxy, became unstable and collapsed inwards on itself under the influence of its own gravity. the dust in the cloud had the same chemical composition as the sun and chondritic meteorites. gravity brought most of the gas and dust together in a single central mass but some of the gas and dust became spread out in a flat disk rotating around the sun. the dust included an abundance of olivine-rich grains and bits of metal and it eventually clumped together to form larger objects, ending with planets and asteroids, all orbiting the sun. the gas was lost from the asteroids and the inner, terrestrial planets because their gravity was too weak to hold on to it, but the gas did stick to jupiter and the other icy-cold giant planets beyond.

earth began as a mixture of about 90% stony, olivine-rich material and about 10% iron metal, just like the composition of chondritic meteorites. soon after its formation the interior of the earth is thought to have become very hot. what was the result of this increase in heat?

a)
the iron melted and collected in the interior of earth to become its core.

b)
the olivine remained behind, becoming the mantle and the melted iron became the core.

c)
both the olivine and iron melted and as they later solidified, became the mantle and the core.

d)
the olivine became the crust and the iron, melting, defended into the earth to become the core.