Carbon-depleted outer core revealed by sound velocity measurements of liquid iron–carbon alloy

Nakajima, Yoichi; Imada, Saori; Hirose, Kei; Komabayashi, Tetsuya; Ozawa, Haruka; Tateno, Shigehiko; Tsutsui, Satoshi; Kuwayama, Yasuhiro; Baron, Alfred Q. R.

doi:10.1038/ncomms9942

Cited by 61 publications

(106 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent works studying the p-wave velocity of molten iron at up to 70 GPa (ref. 35) and estimating the low temperature at the top of the core36 strongly suggest the presence of hydrogen in the core, something to which the present study adds further evidence.…”

Section: Discussionsupporting

confidence: 76%

Hydrogenation of iron in the early stage of Earth’s evolution

et al. 2017

View full text Add to dashboard Cite

Density of the Earth's core is lower than that of pure iron and the light element(s) in the core is a long-standing problem. Hydrogen is the most abundant element in the solar system and thus one of the important candidates. However, the dissolution process of hydrogen into iron remained unclear. Here we carry out high-pressure and high-temperature in situ neutron diffraction experiments and clarify that when the mixture of iron and hydrous minerals are heated, iron is hydrogenized soon after the hydrous mineral is dehydrated. This implies that early in the Earth's evolution, as the accumulated primordial material became hotter, the dissolution of hydrogen into iron occurred before any other materials melted. This suggests that hydrogen is likely the first light element dissolved into iron during the Earth's evolution and it may affect the behaviour of the other light elements in the later processes.

show abstract

Section: Discussionsupporting

confidence: 76%

Hydrogenation of iron in the early stage of Earth’s evolution

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Extrapolation to higher pressures of our density measurements are quite close to density calculated from sound velocity measurements on liquid Fe‐C alloys in LH‐DAC (Nakajima et al, ) and fall somewhat below the values obtained by molecular dynamics simulations (Badro et al, ) (Figure , right). However, in view of the relatively large extrapolation from our highest pressure point (58 GPa) to the core‐mantle boundary (CMB) pressure (136 GPa), we can consider these two data sets in overall agreement with our experimental results.…”

Section: Resultscontrasting

confidence: 59%

“…(inset) Zoom over the lower‐pressure range. (right) Expanded view around the CMB pressure showing our extrapolated EoS and the comparison with previous studies (Badro et al, ; Ichikawa et al, ; Nakajima et al, ).…”

Section: Resultsmentioning

confidence: 90%

Structure and Density of Fe‐C Liquid Alloys Under High Pressure

et al. 2017

View full text Add to dashboard Cite

The density and structure of liquid Fe‐C alloys have been measured up to 58 GPa and 3,200 K by in situ X‐ray diffraction using a Paris‐Edinburgh press and laser‐heated diamond anvil cell. Study of the pressure evolution of the local structure inferred by X‐ray diffraction measurements is important to understand the compression mechanism of the liquid. Obtained data show that the degree of compression is greater for the first coordination sphere than the second and third coordination spheres. The extrapolation of the measured density suggests that carbon cannot be the only light element alloyed to iron in the Earth's core, as 8–16 at % C (1.8–3.7 wt % C) would be necessary to explain the density deficit of the outer core relative to pure Fe. This concentration is too high to account for outer core velocity. The presence of other light elements (e.g., O, Si, S, and H) is thus required.

show abstract

“…During the differentiation into core and mantle, this carbon could partly be dissolved in the core material, leaving a mantle depleted in carbon. This is derived from recent studies that found that the outer core of Earth may contain some carbon at the 1% weight level (Nakajima et al 2015;Wood et al 2013). 6.…”

Section: Carbon Content Of Planetesimalsmentioning

confidence: 99%

Spatial distribution of carbon dust in the early solar nebula and the carbon content of planetesimals

Gail

Trieloff

2017

A&A

View full text Add to dashboard Cite

Context. A high fraction of carbon bound in solid carbonaceous material is observed to exist in bodies formed in the cold outskirts of the solar nebula, while bodies in the region of terrestrial planets contain only very small mass fractions of carbon. Most of the solid carbon component is lost and converted into CO during the spiral-in of matter as the Sun accretes matter from the solar nebula. Aims. We study the fate of the carbonaceous material that entered the proto-solar disc by comparing the initial carbon abundance in primitive solar system material and the abundance of residual carbon in planetesimals and planets in the asteroid belt and the terrestrial planet region. Methods. We constructed a model for the composition of the pristine carbonaceous material from observational data on the composition of the dust component in comets and of interplanetary dust particles and from published data on pyrolysis experiments. This material entered the inner parts of the solar nebula during the course of the build-up of the proto-sun by accreting matter from the proto-stellar disc. Based on a one-zone evolution model of the solar nebula, we studied the pyrolysis of the refractory and volatile organic component and the concomitant release of hydrocarbons of high molecular weight under quiescent conditions of disc evolution, while matter migrates into the central parts of the solar nebula. We also studied the decomposition and oxidation of the carbonaceous material during violent flash heating events, which are thought to be responsible for the formation of chondrules. To do this, we calculated pyrolysis and oxidation of the carbonaceous material in temperature spikes that were modeled according to cosmochemical models for the temperature history of chondrules. Results. We find that the complex hydrocarbon components of the carbonaceous material are removed from the disc matter in the temperature range between 250 and 400 K, but the amorphous carbon component survives to temperatures of 1200 K. Without efficient carbon destruction during flash-heating associated with chondrule formation, the carbon abundance of terrestrial planets, except for Mercury, would be of several percent and not as low as it is found in cosmochemical studies. Chondrule formation seems to be a crucial process for the carbon-poor composition of the material of terrestrial planets.

show abstract

Carbon-depleted outer core revealed by sound velocity measurements of liquid iron–carbon alloy

Cited by 61 publications

References 51 publications

Hydrogenation of iron in the early stage of Earth’s evolution

Hydrogenation of iron in the early stage of Earth’s evolution

Structure and Density of Fe‐C Liquid Alloys Under High Pressure

Spatial distribution of carbon dust in the early solar nebula and the carbon content of planetesimals

Contact Info

Product

Resources

About