کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4676913 1634708 2016 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Differentiated planetesimal impacts into a terrestrial magma ocean: Fate of the iron core
ترجمه فارسی عنوان
تأثیرات سیارات مختلف را به یک اقیانوس ماگمای زمینی تقسیم می کند: سرنوشت هسته آهن
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
چکیده انگلیسی


• We model differentiated planetesimal impacts into a terrestrial magma ocean.
• The iron core disperses into a much larger volume of liquid silicate.
• We demonstrate that accretionary impacts greatly distort the iron core.
• The impact determines the initial condition of the iron core prior to entrainment.
• The impact dispersion implies larger iron cores can chemically equilibrate.

The abundance of moderately siderophile elements (“iron-loving”; e.g. Co, Ni) in the Earth's mantle is 10 to 100 times larger than predicted by chemical equilibrium between silicate melt and iron at low pressure, but it does match expectation for equilibrium at high pressure and temperature. Recent studies of differentiated planetesimal impacts assume that planetesimal cores survive the impact intact as concentrated masses that passively settle from a zero initial velocity and undergo turbulent entrainment in a global magma ocean; under these conditions, cores greater than 10 km in diameter do not fully mix without a sufficiently deep magma ocean. We have performed hydrocode simulations that revise this assumption and yield a clearer picture of the impact process for differentiated planetesimals possessing iron cores with radius = 100 km that impact into magma oceans. The impact process strips away the silicate mantle of the planetesimal and then stretches the iron core, dispersing the liquid iron into a much larger volume of the underlying liquid silicate mantle. Lagrangian tracer particles track the initially intact iron core as the impact stretches and disperses the core. The final displacement distance of initially closest tracer pairs gives a metric of core stretching. The statistics of stretching imply mixing that separates the iron core into sheets, ligaments, and smaller fragments, on a scale of 10 km or less. The impact dispersed core fragments undergo further mixing through turbulent entrainment as the molten iron fragments rain through the magma ocean and settle deeper into the planet. Our results thus support the idea that iron in the cores of even large differentiated planetesimals can chemically equilibrate deep in a terrestrial magma ocean.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 448, 15 August 2016, Pages 24–33
نویسندگان
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