formation of the moon

moons birth story

Astronomers have carried out computer simulations that are consistent with these facts and have detailed a birth story for the Moon. A little more than 4.5 billion years ago, roughly 70 million years after Earth formed, planetary bodies were being pummeled by asteroids and planetoids of all kinds. Earth was struck by a Mars-sized asteroid (Figure 1.1). An artists depiction of the impact that produced the Moon. The tremendous energy from the impact melted both bodies. The molten material mixed up. The dense metals remained on Earth but some of the molten, rocky material was flung into an orbit around Earth. It eventually accreted into a single body, the Moon. Since both planetary bodies were molten, material could differentiate out of the magma ocean into core, mantle, and crust as they cooled. Earths fast spin is from energy imparted to it by the impact.

textbook_image

moon rocks

Lunar rocks reveal an enormous amount about Earths early days. The Genesis Rock, with a date of 4.5 billion years, is only about 100 million years younger than the solar system (see opening image). The rock is a piece of the Moons anorthosite crust, which was the original crust. Why do you think Moon rocks contain information that is not available from Earths own materials? Can you find how all of the evidence presented in the bullet points above is present in the Moons birth story?

how the moon formed

One of the most unique features of planet Earth is its large Moon. Unlike the only other natural satellites orbiting an inner planet, those of Mars, the Moon is not a captured asteroid. Understanding the Moons birth and early history reveals a great deal about Earths early days.

features of the moon

To determine how the Moon formed, scientists had to account for several lines of evidence: The Moon is large; not much smaller than the smallest planet, Mercury. Earth and Moon are very similar in composition. Moons surface is 4.5 billion years old, about the same as the age of the solar system. For a body its size and distance from the Sun, the Moon has very little core; Earth has a fairly large core. The oxygen isotope ratios of Earth and Moon indicate that they originated in the same part of the solar system. Earth has a faster spin than it should have for a planet of its size and distance from the Sun. Can you devise a birth story for the Moon that takes all of these bits of data into account?

instructional diagrams

No diagram descriptions associated with this lesson

questions

apollo astronauts brought back a rock from the moon that is

a) unknown and unknowable.

b) the same age as the formation of the solar system.

-->  c) 100 million years younger than the formation of the solar system.

d) 1 billion years older than the formation of the solar system.

the size of the moon is comparable to the planet _____.

a) jupiter

-->  b) mercury

c) mars

d) saturn

the moon is similar in composition as the planet

-->  a) earth

b) mars

c) uranus

d) neptune

the story of how the moon formed had to account for

a) carbon isotope ratios indicating that earth and moon formed in the same part of the solar system.

b) the similar size of earth and moons cores.

-->  c) earths faster than expected spin.

d) all of these

the moon formed at the same time earth formed.

a) true

-->  b) false

the __ ratios of moon and earth indicate that they originated in the same part of the solar system.

a) hydrogen isotope

-->  b) oxygen isotope

c) neon isotope

d) dust

moons story began when

a) a tremendous number of asteroids hit earth.

b) the sun flung material out into this part of space.

c) earth split into two equal bodies.

-->  d) a mars-sized asteroid hit earth.

the material that came together to form the moon was flung into space from

-->  a) earth.

b) the sun.

c) jupiter.

d) none of these.

the genesis rock is a piece of the moons original crust.

-->  a) true

b) false

in the early solar system, there was a lot of debris asteroids, comets and planetoids - flying around.

-->  a) true

b) false

diagram questions

No diagram questions associated with this lesson