Did Moon form from Earth? - Moon formation

Moons (natural satellites) are those celestial bodies that revolve around a specific planet the same way planets revolve around the sun.

There are eight planets in our solar system, and most have their own moons except Mercury and Venus. It is the funniest fact that not only planets but also even tiny asteroids can have moons. But we generally refer only those large bodies, which are revolving around the planets, as the real moons.

We are not sure how many moons are totally therein the solar system even now. But we are discovering many along the way.

Totally we have discovered about 200 moons and the major portion of it is contributed by Saturn and Jupiter. Even Pluto(which is not treated as a planet) does have five moons. You remember: actually, Pluto is smaller than our earth’s moon! And one of these moons(called by the name ‘Charon’) is larger than its mother planet(Pluto) which is the cause of the abnormal movement of pluto from side to side.

Jupiter has four large moons and these moons are lying in such a fashion that resembles the solar system in which Jupiter takes the role of the massive sun. These all four moons are believed to be formed along with Jupiter.

Now, what about our Moon that comes all night in our dark sky with a bright smile(this statement is not correct as the moon can also come in the daytime and it’ll not strictly visible all night(philosophical words don’t care about science!)).

Our moon and the mystery about its formation

Earth has only one natural satellite and that’s our Moon. Moon has a predominant role in slowing the rotation of the earth and thereby making it a planet on which life can take birth and survive (will be discussed at last).

Moon is a main discussed issue in the scientific world. Its formation has been a matter of great debate among scientists. We have knowledge of the moon’s past according to the samples we got from the moon and so.

Our prevailing beliefs on the creation of the moon are viable to change according to the upcoming new research. The one which explains the facts will remain accepted until another come with a more powerful base

Actually, according to scientific research, it is wildly accepted that the moon formed long after the creation of our solar system(the creation of earth and other planets). It is estimated that approximately 30-50 years after the formation of the earth, there was no moon there. This came to be a dilemma for researchers wondering what might be the cause for its formation.

As this matter came to be a source of great controversies, many theories came to exist among different scientists. Among them, the most accepted and the most popular one today is the giant impact hypothesis.

According to NASA, the theories on the formation of the Moon must give the reasons for the results that scientists got by experimenting with the samples collected from the moon through various space missions, and some common facts about the moon.

Theories must satisfy:

The low density of Moon
The relative abundance of oxygen isotopes on the moon and on earth are identical. (this implies that the moon and earth must have formed at the same distance from the sun)
Though the samples collected from the moon's crust resemble that of the earth’s, the samples from the deep mantle of moon were much heavier than compared to the earth’s.
Moon rocks contain no volatile substances(substances which easily vapourise on applying heat). (this implies the extra baking of the moon than earth)

Here are some of the main theories with strong bases:

Theories on the formation of the moon.

Before reading this, you must have to have an idea of how the Earth did form.

Giant impact hypothesis

This is the main theory that is presently accepted.

This theory states that long times after the formation of the earth, just when the earth changed from its molten crust to a solid one, collided with a giant asteroid which is similar to the size of Mars.

Most of the part of that huge planet-sized body which is named Theia and the earth’s crust got off spread to space and started revolving around the earth to form a disc-shaped mass circling the earth.

Eventually, these particles did collide and clumped together to form the Moon.

Many other planets’ moons had formed at the same time when the solar nebulae turned into the Solar system(ie: formed along with the planets). But ours is an exception.

Why did Thia smash onto the earth?

At the time when the planets were young(young solar system), the solar system was vigorous and violent. Planets, asteroids and all the other bodies in the solar system were in random motion. So there’s nothing unusual that the earth grabbed the body which went closer to it due to gravitational force of attraction.

Here are some of the proofs (by giving explanations on the perspective of giant impact theory) for the main research outcomes.

Proofs:

why the moon has a lower density.

Moon is made up of lighter materials making it less dense than earth. Moon is made up of materials from the earth's crust majorly and a few from Theia's core which are thrown up when Theia crashed with the earth. On every celestial object, denser materials sink inside to the core and the crust is made up of less dense materials. This is the same thing on earth too. As earth's crust is less dense and the moon is majorly made up of earth’s crust, it is less dense.

(Actually, the moon has a relatively small iron core according to its size. The iron core of Theia might have fused with the earth’s core)

The Moon rocks brought by Apollo astronauts revealed that the isotopes of oxygen in those rocks are only a little different from what found on Earth. But those samples that were taken from the deep lunar mantle are much heavier than those on earth.

This again proves that most of the part of the moon is made up of the earth's crust and of the inner part is of Theia.

It is calculated that the Earth-Moon system has high angular momentum than any other planet.

This suggests the possibility of a giant impact happened which supplied this high momentum

Moon samples show that the moon was a molten body once.

This can be because of the collision of particles that revolved around the earth (the particles thrown away to space when Theia collided with the earth) which clumbed together to form the moon.

Moon has no volatile elements compared to earth.

The volatile elements could be lost in this high-energy event as vapour. And the low gravity of the moon might not able to recapture them.

etc.

Capture theory

People who believe in this theory say that the moon was formed somewhere else in the Solar system and was really captured by the earth when it come closer to the earth. (somebody strongly believes that the moon was taken from Venus)

The moons of mars Phobos and Deimos (both are smaller) are thought to be captured asteroids of mars. Triton of Neptune is also treated as a captured satellite.

Drawbacks:

Other captured satellites are not spherical(they look something like potatoes). But the moon is somewhat spherical.
Captured planets spin in opposite directions to that of the parent planet but the moon is not like that. It spins in the same direction as the earth.
It does not explain why moon materials show similarities to earthly ones(mainly similarity in oxygen isotopes)
This theory wasn’t able to give a proper explanation on why moon rocks are extra baked. etc.

Co-formation theory

Also called co-accretion theory and condensation theory.

It states that both earth and the moon formed at the same time from the Solar nebula(4.5 billion years ago). The same way most of the moons in our solar system had formed. Coalescing from those gases and dust of our solar system's protoplanetary disk.

Drawbacks:

The main drawback of this theory is that it came to be answerless on the study that the moon formed years after the formation of Earth and the Solar system.
This theory wasn’t able to give a proper explanation of why moon rocks are extra-baked.
Couldn’t explain the high angular momentum of the earth-moon system.
Couldn’t explain why the moon has a small iron core,

Fission theory

This theory is in the opinion that the moon was formed by the throwing out of (everyday ejection of) materials from earth to space that lasted many times. This is said to be happened because of the high spinning of earth at that time. Gradually as moon formed, Earth’s rotation slowed down considerably.

The present pacific ocean basin is thought to be the part from which the moon came.

This method was proposed by Charles darwin’s son - George darwin.

Drawbacks:

According to this theory, many small moons would have formed instead of a single one.
The gravitational force would bring the materials towards the earth as soon as they eject out.
Couldn’t explain extra baking of the moon.

Some interesting facts about the Moon

Did you know that the moon is really spinning outward over time?

Yeah, it is indeed a true thing that moon is spinning more and more outward from the earth in the course of time. And it is estimated to be one and a half-inch per year. This movement was revealed by the Apollo missions held by NASA. When NASA sent astronauts from three of its Apollo missions, including Apollo 11, they placed certain many reflectors on the lunar(moon) surface that are still being used to find the distance of the moon from the earth more precisely and accurately. It is these reflectors which revealed this phenomenon of ‘going far’.

It is believed that when the moon formed, it was approximately just only about 22500 kilometres from the earth but now it is approximately about 402336 kilometres!

The reason for this expansion in lunar orbit is the tidal interaction of the earth. This is in turn making the earth rotate slowly. When Moon was formed, one day on earth was only about five hours long! It gradually decreased as moon moved further away from the earth. The speed of rotation of the earth can even be slower after many millions of years. Can you imagine a day which is as long as a week?

Without Moon, life may not happen to form on earth!

Moon is a great source for knowing the past of Earth and the Solar system as well why?

This question may be raised in everybody's minds. The answer is simple. On our earth, many processes had been happened and are still changing. It is pretty sure that the soil and the crust we see now are obviously not the same as that of the young earth. But in the case of the moon, there happened not any geological activities as on earth. So the surface of the moon stood dormant. Its heavily cratered surface contains a record of the events that happened in the Solar system and on our planet! So by the moon, we can dig out the faded history.

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Did Moon form from Earth? - Moon formation