The simulation above is about two planets colliding and was made based on a numerical model developed by Dr. Robin M. Canup, a Principal Investigator in NASA’s “Origins of Solar Systems”, “Planetary Geology and Geophysics”, “Outer Planets Fundamental Research”, and LASER programs and NSF’s “Planetary Astronomy” program. In 2003, she published a paper in which 100 hydrodynamic simulations of potential Moon-forming impacts were modeled.
“The most favorable conditions for producing a sufficiently massive and iron-depleted protolunar disk involve collisions with an impact angle near 45 degrees and an impactor velocity at infinity < 4 km/sec. For a total mass and angular momentum near to that of the current Earth–Moon system, such impacts typically place about a lunar mass of material into orbits exterior to the Roche limit, with the orbiting material composed of 10 to 30% vapor by mass.
In all cases, the vast majority of the orbiting material originates from the impactor, consistent with previous findings. By mapping the end fate (escaping, orbiting, or in the planet) of each particle and the peak temperature it experiences during the impact onto the figure of the initial objects, it is shown that in the successful collisions, the impactor material that ends up in orbit is primarily that portion of the object that was heated the least, having avoided direct collision with the Earth,” Canup wrote in the study abstract.
The scope was to find just the right conditions that might explain how the moon was formed, given the leading moon formation theory among scientists is that early-Earth collided with another Mars-sized planet. The lion’s share of the debris coalesced to form the Earth as it is today, while a portion of the Theia (the name of the planet which smashed into Earth) and early Earth mass joined to from the moon.
This theory was first conceived in 1946 by Reginald Aldworth Daly from Harvard University. The impact theory explained many of the challenges about the formation of the Moon. For example, one question was: why do the Earth and Moon have very different-sized cores.
You can find more animated simulations based on Canup’s numerical models here.