Editing Planetary core (section)

=== Cores of the rocky planets ===
The cores of the [[Terrestrial planet|rocky planets]] were initially characterized by analyzing data from spacecraft, such as NASA's [[Mariner 10]] that flew by Mercury and Venus to observe their surface characteristics.<ref>{{Citation|title=Mariner 10 mission highlights : Venus mosaic P-14461 |date=1987|publisher=National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology|oclc=18035258}}</ref> The cores of other planets cannot be measured using seismometers on their surface, so instead they have to be inferred based on calculations from these fly-by observation. Mass and size can provide a first-order calculation of the components that make up the interior of a planetary body. The structure of rocky planets is constrained by the average density of a planet and its [[Moment of inertia factor|moment of inertia]].<ref name="solomon 1979">{{Cite journal |last=Solomon |first=Sean C. |date=June 1979 |title=Formation, history and energetics of cores in the terrestrial planets |journal=Physics of the Earth and Planetary Interiors |language=en |volume=19 |issue=2 |pages=168–182 |bibcode=1979PEPI...19..168S |doi=10.1016/0031-9201(79)90081-5 |issn=0031-9201}}</ref> The moment of inertia for a differentiated planet is less than 0.4, because the density of the planet is concentrated in the center.<ref>{{Cite book|title=Planetary interiors|author=Hubbard, William B.|date=1992|publisher=Krieger Pub. Co|isbn=089464565X|oclc=123053051}}</ref> Mercury has a moment of inertia of 0.346, which is evidence for a core.<ref>{{Cite journal|last1=Margot|first1=Jean-Luc|last2=Peale|first2=Stanton J.|last3=Solomon|first3=Sean C.|last4=Hauck|first4=Steven A.|last5=Ghigo|first5=Frank D.|last6=Jurgens|first6=Raymond F.|last7=Yseboodt|first7=Marie|last8=Giorgini|first8=Jon D.|last9=Padovan|first9=Sebastiano|date=December 2012|title=Mercury's moment of inertia from spin and gravity data: MERCURY'S MOMENT OF INERTIA|journal=Journal of Geophysical Research: Planets|volume=117|issue=E12|pages=n/a|doi=10.1029/2012JE004161|bibcode=2012JGRE..117.0L09M|doi-access=free}}</ref> Conservation of energy calculations as well as magnetic field measurements can also constrain composition, and surface geology of the planets can characterize differentiation of the body since its accretion.<ref>{{Cite journal|last=Solomon|first=Sean C.|date=August 1976|title=Some aspects of core formation in Mercury|journal=Icarus|volume=28|issue=4|pages=509–521|doi=10.1016/0019-1035(76)90124-X|bibcode=1976Icar...28..509S|hdl=2060/19750022908|s2cid=120492617 |hdl-access=free}}</ref> Mercury, Venus, and Mars’ cores are about 75%, 50%, and 40% of their radius respectively.<ref name="de pater 2015">{{Cite book |last1=De Pater |first1=Imke |title=Planetary sciences |last2=Lissauer |first2=Jack Jonathan |date=2015 |publisher=Cambridge University Press |isbn=978-1-107-09161-0 |edition=2nd |location=Cambridge |doi=10.1017/cbo9781316165270.023}}</ref><ref name="stevenson 2001">{{Cite journal |last=Stevenson |first=David J. |date=July 2001 |title=Mars' core and magnetism |journal=Nature |language=en |volume=412 |issue=6843 |pages=214–219 |bibcode=2001Natur.412..214S |doi=10.1038/35084155 |issn=0028-0836 |pmid=11449282 |s2cid=4391025}}</ref>