Planetary core

[10] The internal structure of the Moon was characterized in 1974 using seismic data collected by the Apollo missions of moonquakes.

[13] The cores of the 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.

[14] 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.

[17] 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.

[19][20] Planetary systems form from flattened disks of dust and gas that accrete rapidly (within thousands of years) into planetesimals around 10 km in diameter.

Crystallization of perovskite in an early magma ocean is an oxidation process and may drive the production and extraction of iron metal from an original silicate melt.

Impacts between planet-sized bodies in the early Solar System are important aspects in the formation and growth of planets and planetary cores.

[21] Niobium/tantalum (Nb/Ta) isotopic ratios, when compared with a chondritic reference frame, show mild depletion in bulk silicate Earth and the moon.

[28] Pallasites are thought to form at the core-mantle boundary of an early planetesimal, although a recent hypothesis suggests that they are impact-generated mixtures of core and mantle materials.

[29] Dynamo theory is a proposed mechanism to explain how celestial bodies like the Earth generate magnetic fields.

Examples of compositional buoyancy include precipitation of iron alloys onto the inner core and liquid immiscibility both, which could influence convection both positively and negatively depending on ambient temperatures and pressures associated with the host-body.

[30] This value is calculated from a variety of factors: secular cooling, differentiation of light elements, Coriolis forces, radioactive decay, and latent heat of crystallization.

[20] Current understanding of the outer planets in the solar system, the ice and gas giants, theorizes small cores of rock surrounded by a layer of ice, and in Jupiter and Saturn models suggest a large region of liquid metallic hydrogen and helium.

[19] The properties of these metallic hydrogen layers is a major area of contention because it is difficult to produce in laboratory settings, due to the high pressures needed.

[33] The composition of the iron-rich core remains uncertain, but it likely contains nickel, silicon and perhaps sulfur and carbon, plus trace amounts of other elements.

[34] The composition of Venus' core varies significantly depending on the model used to calculate it, thus constraints are required.

[26] However, experimental evidence has found that potassium is strongly siderophile when dealing with temperatures associated with core-accretion, and thus potassium-40 could have provided an important source of heat contributing to the early Earth's dynamo, though to a lesser extent than on sulfur rich Mars.

[2] Hf/W isotopes derived from the martian meteorite Zagami, indicate rapid accretion and core differentiation of Mars; i.e. under 10 million years.

The model further concludes that the core of mars is entirely liquid, as the latent heat of crystallization would have driven a longer-lasting (greater than one billion years) dynamo.

[28] Jupiter has an observed magnetic field generated within its core, indicating some metallic substance is present.

[5] Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (greater than Saturn).

[5] Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (but still less than Jupiter).

[37] The Psyche mission, titled “Journey to a Metal World,” is aiming to studying a body that could possibly be a remnant planetary core.

Thus the planet cannot be gaseous, and must be composed of heavier elements that are also cosmically abundant like carbon and oxygen; making it likely crystalline like a diamond.

Internal pressures of such water-worlds would result in exotic phases of water forming on the surface and within their cores.