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Title: Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core

Abstract

Sound velocities of Fe and Fe–S liquids were determined by combining the ultrasonic measurements and synchrotron X-ray techniques under high pressure–temperature conditions from 1 to 8 GPa and 1573 K to 1973 K. Four different liquid compositions were studied including Fe, Fe–10 wt% S, Fe–20 wt% S, and Fe–27 wt% S. Our data show that the velocity of Fe-rich liquids increases upon compression and decreases with increasing sulfur content, whereas temperature has negligible effect on the velocity of Fe–S liquids. The sound velocity data were combined with ambient-pressure densities to fit the Murnaghan equation of state (EOS). Compared to the lunar seismic model, our velocity data constrain the sulfur content at 4±3 wt%, indicating a significantly denser (6.5±0.5 g/cm 3) and hotter (1870-70+100 K) outer core than previously estimated. A new lunar structure model incorporating available geophysical observations points to a smaller core radius. Our model suggests a top–down solidification scenario for the evolution of the lunar core. Such “iron snow” process may have been an important mechanism for the growth of the inner core.

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [2]
  1. Case Western
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Science Foundation (NSF)
OSTI Identifier:
1129241
Resource Type:
Journal Article
Resource Relation:
Journal Name: Earth Planet. Sci. Lett.; Journal Volume: 396; Journal Issue: 06, 2014
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Jing, Zhicheng, Wang, Yanbin, Kono, Yoshio, Yu, Tony, Sakamaki, Tatsuya, Park, Changyong, Rivers, Mark L., Sutton, Stephen R., Shen, Guoyin, CIW), and UC). Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core. United States: N. p., 2014. Web. doi:10.1016/j.epsl.2014.04.015.
Jing, Zhicheng, Wang, Yanbin, Kono, Yoshio, Yu, Tony, Sakamaki, Tatsuya, Park, Changyong, Rivers, Mark L., Sutton, Stephen R., Shen, Guoyin, CIW), & UC). Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core. United States. doi:10.1016/j.epsl.2014.04.015.
Jing, Zhicheng, Wang, Yanbin, Kono, Yoshio, Yu, Tony, Sakamaki, Tatsuya, Park, Changyong, Rivers, Mark L., Sutton, Stephen R., Shen, Guoyin, CIW), and UC). Mon . "Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core". United States. doi:10.1016/j.epsl.2014.04.015.
@article{osti_1129241,
title = {Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core},
author = {Jing, Zhicheng and Wang, Yanbin and Kono, Yoshio and Yu, Tony and Sakamaki, Tatsuya and Park, Changyong and Rivers, Mark L. and Sutton, Stephen R. and Shen, Guoyin and CIW) and UC)},
abstractNote = {Sound velocities of Fe and Fe–S liquids were determined by combining the ultrasonic measurements and synchrotron X-ray techniques under high pressure–temperature conditions from 1 to 8 GPa and 1573 K to 1973 K. Four different liquid compositions were studied including Fe, Fe–10 wt% S, Fe–20 wt% S, and Fe–27 wt% S. Our data show that the velocity of Fe-rich liquids increases upon compression and decreases with increasing sulfur content, whereas temperature has negligible effect on the velocity of Fe–S liquids. The sound velocity data were combined with ambient-pressure densities to fit the Murnaghan equation of state (EOS). Compared to the lunar seismic model, our velocity data constrain the sulfur content at 4±3 wt%, indicating a significantly denser (6.5±0.5 g/cm3) and hotter (1870-70+100 K) outer core than previously estimated. A new lunar structure model incorporating available geophysical observations points to a smaller core radius. Our model suggests a top–down solidification scenario for the evolution of the lunar core. Such “iron snow” process may have been an important mechanism for the growth of the inner core.},
doi = {10.1016/j.epsl.2014.04.015},
journal = {Earth Planet. Sci. Lett.},
number = 06, 2014,
volume = 396,
place = {United States},
year = {Mon Jul 21 00:00:00 EDT 2014},
month = {Mon Jul 21 00:00:00 EDT 2014}
}