When worlds collide: Stunning 3D simulation shows what happens in giant planetary crashes (video)

rod

Oct 22, 2019
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Interesting 1:23 video here. The article stated "Planets evolve over billions of years, as bits of dust and gas clump together. However, planetary formation can be easily disrupted by impacts from other celestial objects. Such collisions can cause a wide range of consequences for young planets, such as atmospheric loss, the 3D simulations suggest. "

Protoplanetary disks used in accretion models do not last *billions of years*, others reading may get this impression. Also synestia phase of matter after giant impacts I did not see reported or in the video simulation. 'Researchers propose new type of planetary object', https://phys.org/news/2017-05-planetary.html
 
Dec 20, 2019
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Reactions: Torbjorn Larsson
Jan 4, 2020
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Seems we are all fascinated by the resolution here! What was most interesting to me is not the loss but the retention, which the last part with contrast colors showed well. As I have started to suspect from rapid planetary formation models, the mantle mixing is not primarily from the original Tellus crust of a complex process of core formation and later "grain rain". The video show the lower mantle as exogenous material from the core of am outer system planetesimal Theia. I'm not sure if it explains the primordial volatile leakage that we see from these deep regions, but assuming a planetary disk centered impactor distribution for Theia it could possibly explain the equatorial distributed masses [ https://en.wikipedia.org/wiki/Large_low-shear-velocity_provinces , https://phys.org/news/2020-06-scientists-unexpected-widespread-earth-core.html ].



 
Jan 4, 2020
204
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Interesting 1:23 video here. The article stated "Planets evolve over billions of years, as bits of dust and gas clump together. However, planetary formation can be easily disrupted by impacts from other celestial objects. Such collisions can cause a wide range of consequences for young planets, such as atmospheric loss, the 3D simulations suggest. "

Protoplanetary disks used in accretion models do not last *billions of years*, others reading may get this impression. Also synestia phase of matter after giant impacts I did not see reported or in the video simulation. 'Researchers propose new type of planetary object', https://phys.org/news/2017-05-planetary.html
Good catch! Seems the author mashed together the two different evolution processes (atmosphere evolution, with or without impcats) and early planet formation.

I think synestias never became much popular among planetary scientists, and the videos may show why, they don't happen for feasible impact velocities and they aren't necessary to explain the impact outcome.
 

rod

Oct 22, 2019
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FYI, this simulation model is important and the article here refers to atmospheric loss during a giant impact event. "Earth's moon is believed to have formed about 4.5 billion years ago following a grazing impact of a small planet about the size Mars with Earth. The debris from this impact accumulated in orbit around Earth to form our moon. The new simulations suggest that this event may have stolen between 10% and 50% of early Earth's atmosphere. "

Here is the NASA ADS Abstract and arXiv PDF report. 'Atmospheric Erosion by Giant Impacts onto Terrestrial Planets: A Scaling Law for any Speed, Angle, Mass, and Density', https://ui.adsabs.harvard.edu/abs/2020arXiv200704321K/abstract

"1. INTRODUCTION Terrestrial planets are thought to form from tens of roughly Mars-sized embryos that crash into each other after accreting from a proto-planetary disk (Chambers 2001). At the same time, planets grow their atmospheres by accreting gas from their surrounding nebula, degassing impacting volatiles directly into the atmosphere, and by outgassing volatiles from their interior (Massol et al. 2016). For a young atmosphere to survive it must withstand radiation pressure of its host star, frequent impacts of small and medium impactors, and typically at least one late giant impact that could remove an entire atmosphere in a single blow (Schlichting & Mukhopadhyay 2018)."

These studies indicate that the proto-Earth could lose 60% of its early atmosphere too. Some impacts remove all of the early atmosphere. How the proto-Earth continued to gain an atmosphere after the postulated giant impact with Theia is not clear to me, consider that the gas in the accretion disk is now depleted by the time of Theia impact. Growing the proto-Earth to its present mass and size needs explaining too. Other simulations get very different results when using low mass stars like red dwarfs. 'Ejection of close-in super-Earths around low-mass stars in the giant impact stage', https://ui.adsabs.harvard.edu/abs/2020arXiv200714039M/abstract, "Earth-sized planets were observed in close-in orbits around M dwarfs. While more and more planets are expected to be uncovered around M dwarfs, theories of their formation and dynamical evolution are still in their infancy. We investigate the giant impact growth of protoplanets, which includes strong scattering around low-mass stars..."

A rich area of study with enormous kinetic energies and the potential for much destruction of proto-planets and the proto-Earth too :)
 
Nov 29, 2020
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Coppied from above: "FYI, this simulation model is important and the article here refers to atmospheric loss during a giant impact event. "Earth's moon is believed to have formed about 4.5 billion years ago following a grazing impact of a small planet about the size Mars with Earth. The debris from this impact accumulated in orbit around Earth to form our moon. The new simulations suggest that this event may have stolen between 10% and 50% of early Earth's atmosphere. "
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Has any study of this models looked at Mars having grazing impact with Mercury instead of earth?
I strongly believe the two planets had contacts in the past.
 

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