What is the most widely accepted theory of the moon's origin?
1 Answer
At the time Earth formed 4.5 billion years ago, other smaller planetary bodies were also growing. One of these hit earth late in Earth's growth process, blowing out rocky debris. A fraction of that debris went into orbit around the Earth and aggregated into the moon.
Explanation:
The Idea in a Nutshell
At the time Earth formed 4.5 billion years ago, other smaller planetary bodies were also growing. One of these hit earth late in Earth's growth process, blowing out rocky debris. A fraction of that debris went into orbit around the Earth and aggregated into the moon.
Why this is a good hypothesis
• The Earth has a large iron core, but the moon does not. This is because Earth's iron had already drained into the core by the time the giant impact happened. Therefore, the debris blew out of both Earth and the impactor came from their iron-depleted, rocky mantles. The iron core of the impactor melted on impact and merged with the iron core of Earth, according to computer models.
• Earth has a mean density of 5.5 grams/cubic centimeter, but the moon has a density of only 3.3 g/cc. The reason is the same, that the moon lacks iron.
• The moon has exactly the same oxygen isotope composition as the Earth, whereas Mars rocks and meteorites from other parts of the solar system have different oxygen isotope compositions. This shows that the moon formed from material formed in Earth's neighborhood.
• If a theory about lunar origin calls for an evolutionary process, it has a hard time explaining why other planets do not have similar moons. (Only Pluto has a moon that is an appreciable fraction of its own size.) Our giant impact hypothesis had the advantage of invoking a stochastic catastrophic event that might happen only to one or two planets out of nine.
[https://www.psi.edu/epo/moon/moon.html ]
Hope this helps! :)
