A special giant impact and its influence on Earths core and mantle

Status Report From: e-Print archive
Posted: Thursday, January 3, 2019

You Zhou, Christian Reinhardt, Hongping Deng, Cao Xiaobin, Yun Liu

(Submitted on 2 Jan 2019)

It is believed that tens of giant impacts had happened during the accretion of Earth. How these giant impacts occur has significant influence on the chemistry and physics of Earths mantle and core. Although the core-merging giant impact (CMGI) has been proposed by previous researchers, its occurrence and consequence are not well understood yet. Here the occurrence conditions of a CMGI had been studied via 800 runs of smoothed particle hydrodynamics simulations. The results show that a CMGI can occur only if the impact angle and velocity are small and the impactors mantle is thick. Based on the obtained conditions for the occurrence of the CMGI and the impacting probabilities suggested by astrophysics, 100,000 Monte Carlo simulations were performed to find out the probability of CMGI occurrence during the entire accretion history of Earth. The results show that 7.29 percent materials in Earths core might be delivered by CMGIs statistically. Meanwhile, CMGIs can bring small amount of silicates into the core. The reaction between these silicates and core metal might largely affect elements partitions between them. In addition, these silicates would quickly ascend to the core-mantle boundary due to density deficit, which might result in the iron-rich ultra-low velocity zones (ULVZs). The mass, shapes, and discontinuous distribution of ULVZs can all be explained. The negative 182W anomalies observed in certain OIBs, thought to be originated from the regions of ULVZs, can also be understandable. Recently, a few studies suggested that the moon-forming giant impact was also a CMGI. If so, our modeling results indicate that a reevaluation is needed for the highly siderophile elements of the mantle and the mass delivered during the late veneer stage.

Comments: 34 pages

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:1901.00420 [astro-ph.EP] (or arXiv:1901.00420v1 [astro-ph.EP] for this version)

Submission history

From: You Zhou 

[v1] Wed, 2 Jan 2019 15:39:25 UTC (2,851 KB)

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