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The impact that formed the Moon may have splashed in the ocean of the Earth's magma


The image of a small object & # 39, breaking and uncoupling from the Earth.
increase / An early version of the collision model, showing the frontal impact.

Earth and its monthly unique in our solar system. Land with & # 39; is the only rocky planet with a large moon, and the only dwarf planet Pluto has a moon, which is so similar to the size of the host planet. Month also strikingly similar to Earth in terms of its composition, assuming that they are formed from the same material as the pool instead of the month of elsewhere and passionate about the future.

This set of properties led to a number of ideas about how the Moon formed, all of which failed to pick up the data in different ways. In the end, however, scientists have come up with an idea that seemed to get the most out of the big picture right: a collision between Earth and a & # 39; an object the size of Mars occurred in the early history of the solar system, creating a cloud of debris about the & # 39; united in the Moon,

Despite the fact that there are fundamental features of our system of two bodies of law, there are still some subtle differences that have not been solved by the impact model. Now a team of Japanese researchers say that there is a way to tidy up some of the loose ends: the impact of having to take place while the ground was covered in molten magma ocean.

Close, but not quite right

Smashing of the & # 39; object the size of Mars to Earth size planets can easily produce something that looks very similar to the Earth-Moon system. If exposure occurs obliquely, you end up with the right amount of angular momentum in the orbits of the two bodies. These events dump a lot of iron in the core of the impactor of the Earth and the Moon ends with a lot of material to the proto-Earth, explaining their similar composition.

But there are a few nagging details that do not quite turn out. For example, the moon has more iron oxide than the earth, assuming that the two bodies, which had encountered a variety of formulations. But the ratio of different isotopes, which we tested, indicates that the Earth and Moon are almost identical, indicating that they should be started with a very similar structure. The combination of these two facts, it was not easy.

But the researchers behind the new work have decided to review the physics of collisions, rather than the composition of face organs. In the early history of our solar system, even after the major planets formed there was a lot of debris left. Many of those on the & # 39 objects will eventually be visible planets, creating a constant stream of influences. The energy released by these impacts may be enough to melt the surface of the planet, creating a magma ocean, globally or near the equator. So that when the Moon forming impact occurred while the Earth has been in a phase of magma ocean?

To find out, the researchers first had to update the software used to simulate these effects. It is generally for the treatment of both & # 39 objects involved in the impact as a collection of solid material. Thus, they changed the existing code so that it could handle the border in density, which occur at the ocean of magma and solid mantle underneath. With that in place, they started smashing things with each other.

big splash

In a typical punches, the lower body comes apart, forming an arc which is a little like an orange peel opening up (without orange inside). The core of the hammer ends leaving most of the rest of the planet and form lumps that fall on Earth, migrate to the nucleus, leaving the poor iron fragments. At the same time, most of the magma ocean separated from the earth, eventually in the form of a spray that both the wire and pull the remnants of the hammer. Shortly after, as another clump drummer splashing in the remains of the magma ocean, putting more of it into orbit around the Earth balances. In the end, almost half of the magma ocean ends are ejected into space.

The research team conducted several experiments with different initial conditions in order to get an idea of ​​the range of outcomes that these collisions could produce. In order to be a viable solution, the clash is necessary to create a system with the right angular momentum, the right weight, and chemistry, which is consistent with what we know about the distribution of elements in the two bodies. The latter condition involves such things as iron-rich core in the world, the excess iron oxide in the moon and similar isotope ratios.

Two of them are from the & # 39 are questions. Most collisions end up with most of the metallic iron in the world, and they all get the correct torque in the target system. This means that a huge range of conditions consistent with these physical constraints on the model. Less weight was limiting where the results var & # 39; Irawan from about half the mass of the moon 1.4 times the mass of the moon. As a rule, you will receive more junk drive if oblique collision and at a lower speed, so that limits the impact the condition bit.

The time course of a typical giant impact on the efforts of the simulation. «SRC =" .20-AM-640x268.png "width =" 640 "height =" 268 "srcset =" 30 to 10: 38: 20-AM.png 2x
increase / The time course of a typical giant impact on the efforts of the simulation.

But the main difference was the presence in the modeling of the magma ocean. Calculations have shown that the presence of the magma ocean is a sharp change in the shock heating that occurs in the collision. If the magma ocean deeper than 500K, much of the ocean gets into orbit. This is partly because it is already hot magma ocean is heated more effectively in a collision. Since more than the proto-Earth orbit gets, the higher the proportion of the moon ends consist of this material, or more specifically, the material of magma ocean.

The higher the proportion of the material with the proto-earth means that the moon formed from isotopic fraction similar to Earth. Moreover, iron oxide has a relatively low melting point, which should accommodate more magma it in the ocean. This explains the relative abundance of the moon made of this material. With more than initiating the Moon in the proto-Earth means that restrictions on the & # 39 object that collided with him so tightly. As a result, researchers believe that the drummer can arise from two different classes of starting material, instead of the same material as the earth formed with.

Thus, a new idea, it seems, takes a dominant explanation for the formation of the moon-sighting giant and refines it a bit. However, he tidies up a few discrepancies between the existing models and the impact of the data that we have created over the last few decades. In many ways, this is a good example of how science usually works: instead of discarding ideas, if they do not quite match up with reality, scientists usually specify tweaking their ideas in order to better fit the data.

nature Geoscience, 2019 DOI: 10.1038 / s41561-019-0354-2 (about Dois).

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