Finally, the density of the Moon is much lower than that of the Earth. The Moon has a low density compared to the terrestrial planets. Recent findings even suggest that the moon’s core constitutes only 2-4 percent of its total mass, compared to a terrestrial core with about 30 percent of the Earth’s mass. Therefore, the differences between the Moon and the Earth greatly weaken the giant-impact theory. ( X: G2 i/ [9 N _ Professor: # m6 G/ e. B" o8 j/ V2 I3 Y While the giant –impact of how the Moon formed has been heavily criticized, I do not find these criticisms convincing. Here is why.
First of all, it is true that so far no trace of a giant impact has been found on the surface of the Earth. Yet we should remember that the giant crash took place more than four billion year ago. Any trace of the collision might have been erased by the force of nature. The Earth’s surface is made up of a number of enormous rock plates and they have collided with each other over millions of years, resulting in tremendous change in the map of the planet. Therefore, if there had been any impact mark might have disappeared long ago.' g: I) s. j8 b: n* F7 E! E Second, it is a fact that tocks on the Moon do not contain water, while those on Earth do. However, as the Moon formed out of the collision of space rocks, the heat from the collision made the entire Moon molten. The temperatures on this newly formed Moon were extremely high. With such high temperatures, any water there might have evaporated and gone off into space. So, the absence of water on the Moon is not surprising. Finally, we know that the density of the Earth’s surface is lower than that of the Earth’s center. Since the Moon was originally part of the Earth’s surface, not the Earth’s core, its density should be consistent with the density of the Earth’s surface. This is exactly what we find. The density of the Moon is consistent with that of the Earth’s surface, which further supports the giant-impact theory of the Moon’s formation. |
