480:
296:
408:
27:
71:
2431:
539:
and pressures is much higher than previously thought imply that core cooling was largely by conduction not convection, limiting the ability of thermal convection to drive the geodynamo. This conundrum is known as the new "core paradox." An alternative process that could have sustained Earth's
575:. The rate of cooling by conduction and convection is uncertain, but one estimate is that the core would not be expected to freeze up for approximately 91 billion years, which is well after the Sun is expected to expand, sterilize the surface of the planet, and then burn out.
140:
of the outer core are about 3,000–4,500 K (2,700–4,200 °C; 4,900–7,600 °F) in its outer region and 4,000–8,000 K (3,700–7,700 °C; 6,700–14,000 °F) near the inner core. Modeling has shown that the outer core, because of its high temperature, is a
172:
As Earth's core cools, the liquid at the inner core boundary freezes, causing the solid inner core to grow at the expense of the outer core, at an estimated rate of 1 mm per year. This is approximately 80,000 tonnes of iron per second.
522:
with large uncertainties suggest that compositional and thermal convection contribute about 80 percent and 20 percent respectively to the power of Earth's geodynamo. Traditionally it was thought that prior to the formation of
374:
in Earth's outer core. For example, accretionary models based on core-mantle element partitioning tend to support proto-Earths constructed from reduced, condensed, and volatile-free material, despite the possibility that
411:
A diagram of Earth's differentiation. The light elements sulfur, silicon, oxygen, carbon, and hydrogen may constitute part of the outer core due to their abundance and ability to partition into liquid iron under certain
121:
are not transmitted through the outer core. Although having a composition similar to Earth's solid inner core, the outer core remains liquid as there is not enough pressure to keep it in a solid state.
214:
compose part of Earth's outer core, as the only feasible way to lower its density. Although Earth's outer core is inaccessible to direct sampling, the composition of light
592:
342:
in BSE compared to CI meteorites may indicate that silicon was absorbed into Earth's core; however, a wide range of silicon concentrations in Earth's outer and
1706:"Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water"
571:
The magnetic field generated by core flow is essential to protect life from interplanetary radiation and prevent the atmosphere from dissipating in the
2202:
424:
compared to chondritic meteorites is attributed to metal-silicate reactions during formation of Earth's core. These reactions are dependent on
984:
Wassel, Lauren; Irving, Jessica; Dues, Arwen (2011). "Reconciling the hemispherical structure of Earth's inner core with its super-rotation".
506:
and also by chemical convection, the exclusion of light elements from the inner core, which float upward within the fluid outer core while
399:
in Earth's outer core, models of Earth's accretion that match these concentrations would presumably better constrain Earth’s formation.
1327:
Mittal, Tushar; Knezek, Nicholas; Arveson, Sarah M.; McGuire, Chris P.; Williams, Curtis D.; Jones, Timothy D.; Li, Jie (2020-02-15).
2268:
483:
A diagram of Earth's geodynamo and magnetic field, which could have been driven in Earth's early history by the crystallization of
857:
De Wijs, Gilles A.; Kresse, Georg; Vočadlo, Lidunka; Dobson, David; Alfè, Dario; Gillan, Michael J.; Price, Geoffrey D. (1998).
2411:
133:
constrain the radius of the outer core to be 3483 km with an uncertainty of 5 km, while that of the inner core is 1220±10 km.
2082:
Tagawa, Shoh; Sakamoto, Naoya; Hirose, Kei; Yokoo, Shunpei; Hernlund, John; Ohishi, Yasuo; Yurimoto, Hisayoshi (2021-05-11).
908:
760:
417:
354:
Tighter constraints on the concentrations of light elements in Earth's outer core would provide a better understanding of
600:
307:. Namely, the light elements contained must have been abundant during Earth's formation, must be able to partition into
2011:"High-Resolution Simulations of The Final Assembly of Earth-Like Planets. 2. Water Delivery And Planetary Habitability"
479:
838:
2455:
2434:
1700:
Rubie, D. C.; Jacobson, S. A.; Morbidelli, A.; O’Brien, D. P.; Young, E. D.; de Vries, J.; Nimmo, F.; Palme, H.;
2358:
1845:
1701:
1626:
Dauphas, Nicolas; Poitrasson, Franck; Burkhardt, Christoph; Kobayashi, Hiroshi; Kurosawa, Kosuke (2015-10-01).
338:
can provide insights into the light element composition of Earth's outer core. For instance, the depletion of
20:
1508:"Shock compression of Fe-Ni-Si system to 280 GPa: Implications for the composition of the Earth's outer core"
649:"Shock compression of Fe-Ni-Si system to 280 GPa: Implications for the composition of the Earth's outer core"
2261:
1945:
83:
1848:; Harries, Dennis; Langenhorst, Falko; Miyajima, Nobuyoshi; Pollok, Kilian; Rubie, David C. (2015-10-15).
2277:
359:
705:
933:
Buffett, Bruce A. (2010). "Tidal dissipation and the strength of the Earth's internal magnetic field".
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503:
194:
of Earth's outer core. In fact, Earth's outer core is approximately 5 to 10 percent lower density than
1898:
1705:
1627:
1506:
Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian (2014-07-15).
1460:
1387:
Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian (2016-03-02).
647:
Zhang, Youjun; Sekine, Toshimori; He, Hongliang; Yu, Yin; Liu, Fusheng; Zhang, Mingjian (2014-07-15).
1459:
Suer, Terry-Ann; Siebert, Julien; Remusat, Laurent; Menguy, Nicolas; Fiquet, Guillaume (2017-07-01).
557:
499:
158:
1774:
Badro, James; Brodholt, John P.; Piet, Hélène; Siebert, Julien; Ryerson, Frederick J. (2015-10-06).
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53:. The outer core begins approximately 2,889 km (1,795 mi) beneath Earth's surface at the
2368:
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524:
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Models of Earth's accretion could be better tested if we had better constraints on light element
2155:
858:
16:
Fluid layer composed of mostly iron and nickel between Earth's solid inner core and its mantle
2460:
2416:
2340:
527:, Earth's geodynamo was mainly driven by thermal convection. However, recent claims that the
343:
107:
46:
1971:
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2095:
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1967:
1910:
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1649:
1628:"Planetary and meteoritic Mg/Si and δ30Si variations inherited from solar nebula chemistry"
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873:
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of these elements in Earth's outer core will help elucidate the conditions of formation of
271:
57:
and ends 5,150 km (3,200 mi) beneath Earth's surface at the inner core boundary.
2220:
2010:
1776:"Core formation and core composition from coupled geochemical and geophysical constraints"
623:
8:
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1429:
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1242:
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966:
889:
802:
777:
686:
1461:"A sulfur-poor terrestrial core inferred from metal–silicate partitioning experiments"
1270:
303:
The variety of light elements present in Earth's outer core is constrained in part by
126:
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2111:
2056:
2048:
1983:
1926:
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421:
299:
An artist's illustration of what Earth might have looked like early in its formation.
50:
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1995:
1755:
1677:
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2040:
1975:
1918:
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1735:
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1584:
1563:
Georg, R. Bastian; Halliday, Alex N.; Schauble, Edwin A.; Reynolds, Ben C. (2007).
1527:
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552:, and other light elements. As the Earth's core began to cool, it would become
492:
162:
37:
is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly
1874:
1849:
1564:
1198:
540:
geodynamo requires Earth's core to have initially been hot enough to dissolve
26:
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2115:
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1987:
1930:
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1809:
1747:
1669:
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1420:
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859:"The viscosity of liquid iron at the physical conditions of the Earth's core"
811:
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682:
515:
437:
371:
211:
150:
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315:, and must not volatilize and escape during Earth's accretionary process.
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1507:
673:
648:
536:
468:
267:
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186:
Earth's outer core cannot be entirely constituted of iron or iron-nickel
137:
1588:
1329:"Precipitation of multiple light elements to power Earth's early dynamo"
1222:
954:
407:
190:
because their densities are higher than geophysical measurements of the
70:
1850:"High pressure metal–silicate partitioning of Ni, Co, V, Cr, Si, and O"
572:
146:
111:
2203:"Earth's core cooling faster than previously thought, researchers say"
1946:"On the water delivery to terrestrial embryos by ice pebble accretion"
1412:
1389:"Experimental constraints on light elements in the Earth's outer core"
157:
in the nickel-iron fluid of the outer core as the principal source of
2246:
1005:
545:
326:
are believed to contain the same planet-forming elements in the same
323:
231:
142:
2084:"Experimental evidence for hydrogen incorporation into Earth's core"
2206:
2009:
Raymond, Sean N.; Quinn, Thomas; Lunine, Jonathan I. (2007-02-01).
1962:
1644:
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may have been absorbed into core-forming metals through a hydrous
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238:. Recent estimates are that Earth's outer core is composed of
1562:
1271:"Light elements in the Earth's outer core: A critical review"
1197:
Wood, Bernard J.; Walter, Michael J.; Wade, Jonathan (2006).
565:
464:
456:
376:
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Implications for Earth's accretion and core formation history
327:
187:
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Fischer, Rebecca A.; Nakajima, Yoichi; Campbell, Andrew J.;
1843:
169:, 50 times stronger than the magnetic field at the surface.
532:
239:
195:
110:, which is solid. Evidence for a fluid outer core includes
38:
1944:
Sato, Takao; Okuzumi, Satoshi; Ida, Shigeru (2016-05-01).
1326:
856:
474:
402:
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909:"First Measurement Of Magnetic Field Inside Earth's Core"
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leading to a different variant of chemical convection.
274:
and the inner core boundary ranges from 4,137 to 4,300
176:
599:. National Geographic. 18 January 2017. Archived from
165:
strength in Earth's outer core is estimated to be 2.5
1899:"Core formation and the oxidation state of the Earth"
1141:
Hirose, Kei; Wood, Bernard; VoÄŤadlo, Lidunka (2021).
1024:"Elasticity and constitution of the Earth's interior"
827:
Global earth physics a handbook of physical constants
387:. If we could better constrain the concentrations of
365:
1199:"Accretion of the Earth and segregation of its core"
2008:
1140:
782:Monthly Notices of the Royal Astronomical Society
510:elements sink. This chemical convection releases
2447:
983:
82: with: speed of convection. You can help by
1780:Proceedings of the National Academy of Sciences
1505:
1386:
646:
622:Sue, Caryl (2015-08-17). Evers, Jeannie (ed.).
1943:
1196:
2262:
710:Annual Review of Earth and Planetary Sciences
447:In another example, the possible presence of
1275:Physics of the Earth and Planetary Interiors
1063:"Density and composition of mantle and core"
906:
2200:
852:
850:
334:, so differences between CI meteorites and
2269:
2255:
778:"The Rigidity of the Earth's Central Core"
2123:
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1961:
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556:in these light elements that would then
478:
451:in Earth's outer core suggests that the
406:
294:
218:can be meaningfully constrained by high-
206:. Hence it has been proposed that light
25:
19:For broader coverage of this topic, see
2153:
1268:
932:
475:Implications for Earth's magnetic field
459:was not limited to the final stages of
403:Consequences for Earth's core formation
383:was accreted towards the conclusion of
21:Internal structure of Earth § Core
2448:
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1839:
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1769:
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1147:Nature Reviews Earth & Environment
1136:
1134:
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1128:
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518:that produces Earth's magnetic field.
2250:
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1021:
1017:
1015:
1897:Wade, J.; Wood, B. J. (2005-07-30).
1499:
1143:"Light elements in the Earth's core"
755:. Academic Press. pp. 101–118.
514:that is then available to power the
177:Light elements of Earth's outer core
64:
1903:Earth and Planetary Science Letters
1834:
1762:
1632:Earth and Planetary Science Letters
1465:Earth and Planetary Science Letters
1333:Earth and Planetary Science Letters
730:10.1146/annurev.ea.15.050187.000325
621:
222:experiments, calculations based on
13:
2140:
1684:
1445:
1377:
1309:
1253:
1181:
1093:
1054:
1012:
803:10.1111/j.1365-246X.1926.tb05385.x
640:
366:Consequences for Earth's accretion
14:
2472:
2242:
1269:Poirier, Jean-Paul (1994-09-01).
907:Staff writer (17 December 2010).
2430:
2429:
2374:D’’ discontinuity (lower mantle)
2369:660 discontinuity (upper mantle)
2364:410 discontinuity (upper mantle)
2156:"Earth's Core and the Geodynamo"
2154:Buffett, Bruce A. (2000-06-16).
829:(3rd ed.). Washington, DC:
776:Jeffreys, Harold (1 June 1926).
318:
232:carbonaceous chondrite meteorite
69:
2213:
2201:David K. Li (19 January 2022).
2194:
2075:
2002:
1937:
1890:
1854:Geochimica et Cosmochimica Acta
1619:
1556:
1067:Journal of Geophysical Research
1028:Journal of Geophysical Research
926:
825:Ahrens, Thomas J., ed. (1995).
753:Physics of the Earth's interior
900:
818:
769:
744:
697:
615:
585:
285:
181:
45:that lies above Earth's solid
30:Earth and atmosphere structure
1:
2180:10.1126/science.288.5473.2007
1565:"Silicon in the Earth's core"
1061:Birch, Francis (1964-10-15).
578:
242:along with 0 to 0.26 percent
60:
1950:Astronomy & Astrophysics
1740:10.1016/j.icarus.2014.10.015
1512:Geophysical Research Letters
1295:10.1016/0031-9201(94)90120-1
653:Geophysical Research Letters
290:
7:
1980:10.1051/0004-6361/201527069
704:Young, C J; Lay, T (1987).
628:National Geographic Society
436:, so better constraints on
102:The outer core of Earth is
10:
2477:
2359:Mohorovičić (crust–mantle)
2108:10.1038/s41467-021-22035-0
1923:10.1016/j.epsl.2005.05.017
1662:10.1016/j.epsl.2015.07.008
1485:10.1016/j.epsl.2017.04.016
1354:10.1016/j.epsl.2019.116030
1159:10.1038/s43017-021-00203-6
831:American Geophysical Union
706:"The Core-Mantle Boundary"
18:
2425:
2392:
2351:
2284:
1875:10.1016/j.gca.2015.06.026
236:bulk silicate Earth (BSE)
2412:Gutenberg (upper mantle)
2393:Regional discontinuities
2045:10.1089/ast.2006.06-0126
751:Gutenberg, Beno (2016).
597:Science & Innovation
379:material from the outer
324:CI chondritic meteorites
278:and from 5,400 to 6,300
226:measurements, models of
1972:2016A&A...589A..15S
1915:2005E&PSL.236...78W
1801:10.1073/pnas.1505672112
1654:2015E&PSL.427..236D
1477:2017E&PSL.469...84S
1345:2020E&PSL.53216030M
1087:10.1029/JZ069i020p04377
1048:10.1029/JZ057i002p00227
1022:Birch, Francis (1952).
2456:Structure of the Earth
2417:Lehmann (upper mantle)
2352:Global discontinuities
500:Earth's magnetic field
496:
413:
300:
159:Earth's magnetic field
125:Seismic inversions of
31:
2088:Nature Communications
482:
410:
298:
250:, 0.8 to 5.3 percent
29:
2379:Core–mantle boundary
1533:10.1002/2014gl060670
674:10.1002/2014gl060670
529:thermal conductivity
512:gravitational energy
418:siderophile elements
272:core-mantle boundary
145:fluid that convects
55:core-mantle boundary
2384:Inner-core boundary
2307:Lithospheric mantle
2225:National Geographic
2172:2000Sci...288.2007B
2166:(5473): 2007–2012.
2100:2021NatCo..12.2588T
2037:2007AsBio...7...66R
1866:2015GeCoA.167..177F
1792:2015PNAS..11212310B
1786:(40): 12310–12314.
1732:2015Icar..248...89R
1589:10.1038/nature05927
1581:2007Natur.447.1102G
1575:(7148): 1102–1106.
1524:2014GeoRL..41.4554Z
1405:2016NatSR...622473Z
1287:1994PEPI...85..319P
1223:10.1038/nature04763
1215:2006Natur.441..825W
1079:1964JGR....69.4377B
1040:1952JGR....57..227B
998:2011NatGe...4..264W
955:10.1038/nature09643
947:2010Natur.468..952B
878:1998Natur.392..805D
794:1926GeoJ....1..371J
722:1987AREPS..15...25Y
665:2014GeoRL..41.4554Z
520:Carnot efficiencies
346:is still possible.
266:by weight, and the
254:, 0 to 4.0 percent
2278:Structure of Earth
1393:Scientific Reports
593:"Earth's Interior"
525:Earth's inner core
504:thermal convection
497:
414:
301:
136:Estimates for the
35:Earth's outer core
32:
2443:
2442:
2405:continental crust
1518:(13): 4554–4559.
1413:10.1038/srep22473
1209:(7095): 825–833.
1073:(20): 4377–4388.
986:Nature Geoscience
762:978-1-4832-8212-1
659:(13): 4554–4559.
461:Earth's accretion
416:The depletion of
385:Earth's accretion
356:Earth's accretion
305:Earth's accretion
234:comparisons with
228:Earth's accretion
114:which shows that
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99:
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2028:astro-ph/0510285
2006:
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330:as in the early
262:, and 5 percent
198:at Earth's core
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2461:Geomagnetism
2335:
2319:Lower mantle
2302:Upper mantle
2228:. Retrieved
2215:
2196:
2163:
2159:
2091:
2087:
2077:
2021:(1): 66–84.
2018:
2015:Astrobiology
2014:
2004:
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1909:(1): 78–95.
1906:
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1702:Frost, D. J.
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631:. Retrieved
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601:the original
596:
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562:lower mantle
537:temperatures
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446:
442:Earth's core
415:
381:Solar System
369:
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332:Solar System
322:
311:iron at low
302:
200:temperatures
185:
171:
135:
131:normal modes
124:
101:
88:
84:adding to it
79:
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33:
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1860:: 177–194.
1638:: 236–248.
918:14 November
913:Science 2.0
788:: 371–383.
607:14 November
558:precipitate
469:magma ocean
455:of Earth’s
412:conditions.
328:proportions
286:Constraints
268:temperature
182:Composition
147:turbulently
138:temperature
119:shear-waves
2450:Categories
2341:Inner core
2336:Outer core
2323:Mesosphere
1963:1512.02414
1716:: 89–108.
1645:1507.02922
1339:: 116030.
633:2022-02-25
579:References
573:solar wind
344:inner core
167:millitesla
127:body waves
112:seismology
108:inner core
61:Properties
47:inner core
2116:2041-1723
2053:1531-1074
1988:0004-6361
1931:0012-821X
1884:0016-7037
1810:0027-8424
1748:0019-1035
1723:1410.3509
1670:0012-821X
1597:1476-4687
1550:128528504
1542:0094-8276
1493:0012-821X
1471:: 84–97.
1421:2045-2322
1371:213919815
1363:0012-821X
1303:0031-9201
1231:1476-4687
1175:237272150
1167:2662-138X
894:205003051
812:1365-246X
738:0084-6597
691:128528504
683:0094-8276
560:into the
546:magnesium
516:geodynamo
463:and that
453:accretion
362:history.
313:pressures
291:Accretion
210:with low
204:pressures
143:viscosity
91:July 2019
2435:Category
2207:NBC News
2188:10856207
2134:33976113
2069:10257401
2061:17407404
1996:55107839
1828:26392555
1756:37592339
1678:20744455
1605:17597757
1439:26932596
1239:16778882
963:21164483
564:forming
535:at core
449:hydrogen
389:hydrogen
377:oxidized
244:hydrogen
220:pressure
216:elements
208:elements
2230:15 July
2168:Bibcode
2160:Science
2125:8113257
2096:Bibcode
2033:Bibcode
1968:Bibcode
1956:: A15.
1911:Bibcode
1862:Bibcode
1819:4603515
1788:Bibcode
1728:Bibcode
1650:Bibcode
1613:1892924
1577:Bibcode
1520:Bibcode
1473:Bibcode
1430:4773879
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1283:Bibcode
1247:8942975
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1036:Bibcode
994:Bibcode
971:4431270
943:Bibcode
874:Bibcode
790:Bibcode
718:Bibcode
661:Bibcode
550:silicon
430:silicon
397:silicon
340:silicon
270:of the
256:silicon
224:seismic
192:density
116:seismic
2400:Conrad
2297:Mantle
2285:Shells
2221:"Core"
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1994:
1986:
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1569:Nature
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866:Nature
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624:"Core"
566:oxides
542:oxygen
508:denser
491:, and
434:sulfur
432:, and
426:oxygen
395:, and
393:oxygen
309:liquid
264:nickel
260:sulfur
252:oxygen
248:carbon
230:, and
149:. The
104:liquid
51:mantle
43:nickel
2321:(aka
2292:Crust
2065:S2CID
2023:arXiv
1992:S2CID
1958:arXiv
1752:S2CID
1718:arXiv
1674:S2CID
1640:arXiv
1609:S2CID
1546:S2CID
1367:S2CID
1243:S2CID
1171:S2CID
967:S2CID
890:S2CID
862:(PDF)
687:S2CID
465:water
457:water
188:alloy
153:sees
2331:Core
2232:2024
2184:PMID
2130:PMID
2112:ISSN
2057:PMID
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1984:ISSN
1927:ISSN
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959:PMID
920:2018
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808:ISSN
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679:ISSN
609:2018
533:iron
358:and
240:iron
202:and
196:iron
141:low-
129:and
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1976:doi
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