The Origin Of The Moon

We investigate the evolution of a circumterrestrial disk of debris generated by a giant impact on the earth and the characteristics of the moon accreted from the disk by using high-resolution N-body simulation. We find that in most cases the disk evolution results in the formation of a single large moon on a nearly non-inclined circular orbit outside the Roche limit, which is consistent with the previous work by Ida et al. (1997). The efficiency of incorporation of disk material into a moon is 10--55%, which increases with the initial specific angular momentum of the disk. These results hardly depend on the initial condition of the disk as long as the mass of the disk is 2 to 4 times the present lunar mass and most mass of the disk exists inside the Roche limit. The time scale of the disk evolution is determined mainly by the surface density of the disk. The evolution of the disk is summarized as follows: The disk contracts through the mutual collisions of disk particles. Gravitational instability takes place and particle clumps grow inside the Roche limit. The clumps are elongated by the Kepler shear, which forms spiral arms (non-axisymmetric structure). Particles are transfered to the outside of the Roche limit due to the gravitational torque exerted by the spiral arms. When a spiral arm is extended beyond the Roche limit, the tip of the spiral arm collapses to form a small moonlet. The rapid accretion of these small moonlets forms a lunar seed. The seed exclusively grows by sweeping up particles transfered over the Roche limit. When the moon becomes large enough to gravitationally dominate the disk, it pushes the rest of the inner disk to the earth. The formation time scale of the moon is of the order of a month.

Category:

Science & Technology

Tags:

• Origin
• Moon

[hotboyclarence]

a head-on collision would have totally disrupted and destroyed the proto-Earth. the collision should have been at a very nigh angle, almost a grazer. A quasi-grazing collision would have disrupted the incoming object, allowing its pieces to fall on earth slowly so that they can be absorbed by proto Earth.

[ERS01254]

I search in Wikipedia. According to them, Theia is the name of the hypothesized planet.

[kikaledecuba]

And finally, at the end of the story, the moon give us the same face without any spin movement, after millions of impacts from the accretion disk. How could believe that story?

[cocoonbreach]

At 1:18. The particles cool down? From what? How do you know which way it was coming from? Is this an unscientific answer to the scientific fact that the evolution model doesn't add up due to the moons retreat from earth?

[fanbutton]

Nice animation, nevertheless, this theory holds no water, for if this really happened, there would have been countless asteroids orbiting the earth today.

[urbania70]

Great simulation. It's interesting that at 5:30 a second, smaller moon, was temporarily formed. This seems in qualitative agreement with the theory (which will be tested by the current NASA GRAIL mission) which states that the different nature of the Moon's hidden side is due to the "splat" of a smaller moon.

[BlossomWolf5]

What's the name of that song??? Reply please!

[jbatts82]

I like the music, who is it?

[themouseman2]

Haha I love it when people waste hours arguing on youtube.

[migraine516]

Cool song.