What is planetary differentiation

When protoplanets accrete more material, the energy at impact causes local heating. In addition to this temporary heating, when a body is large enough then the gravitational force upon a new lump on the surface will create pressures and temperatures which are sufficient to melt some of the materials.

This allows chemical reactions and density differences to mix and separate materials, and soft materials to spread out over the surface.

On Earth , a large piece of molten iron is sufficiently more dense than continental crust material that it can force its way down through the crust to the mantle. In the outer solar system similar effects may take place but the materials may be hydrocarbons such as methane , water ice, or frozen carbon dioxide. Note that some materials may differentiate to regions due to their chemical affinities rather than their densities, "carried along" by other materials that they're associated with; the uranium in Earth's crust is an example.

Materials with a high density tend to sink through lighter materials. This tendency is affected by the relative structural strengths, but such strength is reduced at temperatures where both materials are plastic or molten. Lighter materials try to rise through material with a higher density. On Earth, salt domes are salt deposits in the crust which rise through surrounding rock. Diapirs of other materials exist, and sometimes appear on the surface as mud volcanos.

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How is the acceleration of gravity calculated for planets? Heat sources, other than deposition of impact energy during accretion, are the release of energy through gravitational separation of light and dense constituents, the decay of radioactive heat Skip to main content Skip to table of contents. This service is more advanced with JavaScript available. Encyclopedia of Astrobiology Living Edition.

Editors: Muriel Gargaud, William M. Contents Search. Differentiation, Planetary. Living reference work entry First Online: 02 May How to cite.