Tell About Moon?

The Moon's far side has a crust that is 30 mi (48 km) thicker than that of the near side. This is thought to be because the Moon fused from two different bodies

This hypothesis, although not perfect, perhaps best explains the evidence. Eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists: "You have eighteen months

Go back to your Apollo data, go back to your computer, do whatever you have to, but make up your mind. Don't come to our conference unless you have something to say about the Moon's birth.

At the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most consensual theory.

Before the conference, there were partisans of the three "traditional" theories, plus a few people who were starting to take the giant impact seriously, and there was a huge apathetic middle who didn’t think the debate would ever be resolved. Afterward, there were essentially only two groups: the giant impact camp and the agnostics

Giant impacts are thought to have been common in the early Solar System. Computer simulations of giant impacts have produced results that are consistent with the mass of the lunar core and the angular momentum of the Earth–Moon system.

These simulations also show that most of the Moon derived from the impactor, rather than the proto-Earth.

However, more recent simulations suggest a larger fraction of the Moon derived from the proto-Earth

Other bodies of the inner Solar System such as Mars and Vesta have, according to meteorites from them, very different oxygen and tungsten isotopic compositions compared to Earth.

However, Earth and the Moon have nearly identical isotopic compositions

The isotopic equalization of the Earth-Moon system might be explained by the post-impact mixing of the vaporized material that formed the two, although this is debated

The impact released a lot of energy and then the released material re-accreted into the Earth–Moon system. This would have melted the outer shell of Earth, and thus formed a magma ocean

Similarly, the newly formed Moon would also have been affected and had its own lunar magma ocean; its depth is estimated from about 500 km (300 miles) to 1,737 km (1,079 miles)

While the giant impact hypothesis might explain many lines of evidence, some questions are still unresolved, most of which involve the Moon's composition

In 2001, a team at the Carnegie Institute of Washington reported the most precise measurement of the isotopic signatures of lunar rocks. To their surprise, the rocks from the Apollo program had the same isotopic signature as rocks from Earth, however they differed from almost all other bodies in the Solar System.

Indeed, this observation was unexpected, because most of the material that formed the Moon was thought to come from Theia and it was announced in 2007 that there was less than a 1% chance that Theia and Earth had identical isotopic signatures

Other Apollo lunar samples had in 2012 the same titanium isotopes composition as Earth,[49] which conflicts with what is expected if the Moon formed far from Earth or is derived from Theia.

These discrepancies may be explained by variations of the giant impact hypothesis.

The Moon is a differentiated body. It has a geochemically distinct crust, mantle, and core.

The Moon has a solid iron-rich inner core with a radius possibly as small as 240 kilometres (150 mi) and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometres (190 mi).

Around the core is a partially molten boundary layer with a radius of about 500 kilometres (310 mi).

This structure is thought to have developed through the fractional crystallization of a global magma ocean shortly after the Moon's formation 4.5 billion years ago.

Crystallization of this magma ocean would have created a mafic mantle from the precipitation and sinking of the minerals olivine, clinopyroxene, and orthopyroxene; after about three-quarters of the magma ocean had crystallised, lower-density plagioclase minerals could form and float into a crust atop

The final liquids to crystallise would have been initially sandwiched between the crust and mantle, with a high abundance of incompatible and heat-producing elements

Consistent with this perspective, geochemical mapping made from orbit suggests the crust of mostly anorthosite