(1) the fission theory, in which the moon separated from the earth
during rotation,
(2) the capture theory, in which the earth captured a wandering moon, and
(3) the condensation theory, in which the earth and moon formed from the condensation of the same dust cloud during the formation of the solar system.
Another proposed mechanism is that the moon formed after a collision between the earth and a Mars-sized object that ejected debris out to the current orbit of the moon. The debris coalesced forming the moon and the earth. This mechanism was accepted in the late 20th century, not because of the merits of the theory but because of the shortcomings of the other three theories. The ‘giant impact hypothesis’ has now dominated for over 30 years, but not without major problems for which revised models have been suggested.
Since the geochemical properties of the moon are so similar to those of the earth, the giant impact hypothesis has run into problems. The moon should have a similar composition to the impactor, which should be much different than that of the earth. Numerous computer models have been applied to figure out why the earth and moon are so similar.
This has created a modern crisis in the giant impact concept: if more than half of the moon’s material came from the impactor, how can the moon’s isotopes be nearly identical to the earth’s?
After numerous computer simulations, some scientists now think they have solved the crisis by postulating the Mars-sized object hit a ‘magma ocean’ on the early Earth. In this way, more of the earth material would end up forming the moon. Most models of Earth’s formation postulate a mantle magma ocean caused by the gravitational potential energy of numerous planetesimals transformed into heat. And because a magma ocean is supposed to have more liquid FeO, which accounts for the enrichment of FeO on the moon by a factor of two, it ‘solves’ the problem of higher FeO content on the moon.
In the new simulation with a magma ocean, 70% of the moon would be Earth material, instead of the 40% from previous models. Melosh thinks that the greater proportion of Earth material ejected to form the moon may still not be good enough to explain nearly identical isotopes:
“Although the work of Hosono et al. is an important step towards understanding why the earth and moon are so isotopically similar, it does not wholly resolve the problem. The large changes they report from modifying the SPH code appear to be at odds with the previous validation of the SPH method. The thermodynamic description of the melt used by Hosono et al. must also be improved in future work, to incorporate better thermodynamic models that are valid over the entire range of pressures and temperatures involved in the impact.”
The SPH (Smooth-Particle Hydrodynamic) code includes a “complex necessarily 3D geometry of self-gravitating fluids flowing at supersonic speeds.” And Hosono et al. modified it. It would be very difficult to get such a process correct, which is one reason why Melosh is skeptical.
Hosono et al. state that the many models to explain the problems for the naturalistic origin of the moon are ad hoc, with several glaring problems remaining:
Further, the planetary scientists say that the moon lacks an iron-rich core, which may present a problem in explaining the ancient magnetic field of the moon.
The numerous computer gyrations are really showing that a naturalistic origin of the moon is extremely difficult, if not impossible. The best explanation is given by the Word of God: And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. Genesis 1:16." CMI
Since the geochemical properties of the moon are so similar to those of the earth, the giant impact hypothesis has run into problems. The moon should have a similar composition to the impactor, which should be much different than that of the earth. Numerous computer models have been applied to figure out why the earth and moon are so similar.
This has created a modern crisis in the giant impact concept: if more than half of the moon’s material came from the impactor, how can the moon’s isotopes be nearly identical to the earth’s?
After numerous computer simulations, some scientists now think they have solved the crisis by postulating the Mars-sized object hit a ‘magma ocean’ on the early Earth. In this way, more of the earth material would end up forming the moon. Most models of Earth’s formation postulate a mantle magma ocean caused by the gravitational potential energy of numerous planetesimals transformed into heat. And because a magma ocean is supposed to have more liquid FeO, which accounts for the enrichment of FeO on the moon by a factor of two, it ‘solves’ the problem of higher FeO content on the moon.
In the new simulation with a magma ocean, 70% of the moon would be Earth material, instead of the 40% from previous models. Melosh thinks that the greater proportion of Earth material ejected to form the moon may still not be good enough to explain nearly identical isotopes:
The SPH (Smooth-Particle Hydrodynamic) code includes a “complex necessarily 3D geometry of self-gravitating fluids flowing at supersonic speeds.” And Hosono et al. modified it. It would be very difficult to get such a process correct, which is one reason why Melosh is skeptical.
Hosono et al. state that the many models to explain the problems for the naturalistic origin of the moon are ad hoc, with several glaring problems remaining:
“It should be noted that in all of these models rather ad hoc assumptions are made about the mechanics of GI [giant impact] to explain the chemical similarities between the moon and Earth. It is therefore difficult to explain the angular momentum of the Earth-Moon system in these models.”
Further, the planetary scientists say that the moon lacks an iron-rich core, which may present a problem in explaining the ancient magnetic field of the moon.
The numerous computer gyrations are really showing that a naturalistic origin of the moon is extremely difficult, if not impossible. The best explanation is given by the Word of God: And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. Genesis 1:16." CMI