ORIGIN
What were some earlier ideas?
One early theory was that the moon is a sister world that formed in orbit
around Earth as the Earth formed.
A second early idea was that the moon formed somewhere else in the solar
system where there was little iron, and then was captured into orbit around
Earth.
A third early idea was that early Earth spun so fast that it spun off the moon.
This idea would produce a moon similar to Earth's mantle.
But theses theory failed why The Moon lacks iron, or why lunar rocks showed the same isotope composition as the Earth, or why analysis of the total angular momentum and energy involved indicated that the present Earth-moon system could not form in this way.
New idea!
Two PSI senior scientists, Dr. William K. Hartmann and Dr. Donald R. Davis, were the
first to suggest the leading modern hypothesis of the moon's origin, in a paper published
in 1975 in the journal Icarus.
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.
They reached this conclusion:
The Earth has a large iron core, but the moon does not.
The moon has exactly the same oxygen isotope composition as the Earth. This shows
that the moon formed form 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. 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.
Thus, the giant impact hypothesis continues to be the leading hypothesis on how the moon formed.
Only time will tell, but so far it has stood up to 25 years of scrutiny.
FUTURE
Its future, like its origin, continues being uncertain, since the scientists do not have possible resources. Let us hope someday, to know what will be of us