Home Substantial portion Internal or External Magma Oceans in Early Protoplanets – Perspectives from Nitrogen and Carbon Fractionation

Internal or External Magma Oceans in Early Protoplanets – Perspectives from Nitrogen and Carbon Fractionation


Illustrations illustrating the differentiation regimes of the A) inner and B) outer magmatic oceans. A) Fractionation of N and C between molten alloy and molten silicate in an IMO. B) Fractionation of N and C between atmosphere, molten silicate and molten alloy in an EMO. Figure modified from Elkins-Tanton et al. (2011


As the extent of protoplanetary melting approached magmatic ocean (MO) type conditions, the molten alloys effectively separated from the silicates to form metallic cores.

The nature of the MO of a differentiating protoplanet, i.e. internal or external MO (IMO or EMO), not only determines the abundance of volatile compounds essential for life such as nitrogen (N) and carbon (C) in its core and mantle reservoirs, but also the timing and mechanism of volatile loss.

Whether the first formed protoplanets had IMOs or EMOs, however, is poorly understood. Here, we model the equilibrium partitioning of N and C between alloys and molten silicates in the absence (IMO) or presence (EMO) of vapor-degassed atmospheres. Bulk N and C inventories of protoplanets during core formation are limited for IMOs and EMOs by comparing predicted abundances of N and C in molten alloys of the two scenarios with concentrations of N and C in the parent nuclei of magmatic iron meteorites.

Our results show that compared to EMOs, protoplanets with IMOs satisfy the N and C contents of the parent cores with substantially lower amounts of N and C present in the parent body during core formation. As the bulk N and C contents required for IMO and EMO are in the subchondritic and chondritic range, respectively, splitting models of N and C alone cannot be used to distinguish the prevalence of these two diets. of end-member differentiation.

A comparison of N and C abundances in chondrites with their maximum metamorphic temperatures suggests that protoplanetary interiors could lose a substantial portion of their N and C inventories with increasing degrees of thermal metamorphism.

Damanveer S. Grewal, Johnny D. Seales, Rajdeep Dasgupta

Comments: 19 pages, 8 figures, 1 table
Subjects: Terrestrial and planetary astrophysics (astro-ph.EP)
Cite as: arXiv:2210.03237 [astro-ph.EP] (or arXiv:2210.03237v1 [astro-ph.EP] for this release)
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From: Damanveer Grewal
[v1] Thu, Oct 06, 2022 10:14:05 PM UTC (1,838 KB)