A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opa ...

s, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematica ...

. All terrestrial planets (including

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large list of largest lakes and seas in the Solar System, volumes of water can be found throughout the Solar System, only water distributi ...

), a number of

asteroids An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

, and some planetary

moons A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons ...

have mantles.

Earth's mantle

The Earth's mantle is a layer of silicate rock between the crust and the

outer core Earth's outer core is a fluid layer about thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. The outer core begins approximately beneath Earth's surface at the core-mantle boundary and e ...

. Its mass of 4.01 × 10²⁴ kg is 67% the mass of the Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly solid, but in geological time it behaves as a

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shea ...

. Partial melting of the mantle at

mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a dive ...

s produces

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

, and partial melting of the mantle at

subduction zones Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, t ...

produces

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...

Other planetary mantles

Mercury has a silicate mantle approximately thick, constituting only 28% of its mass. Venus's silicate mantle is approximately thick, constituting around 70% of its mass. Mars's silicate mantle is approximately thick, constituting ~74–88% of its mass, and may be represented by chassignite meteorites.

Moons with mantles

Jupiter's moons Io, Europa, and Ganymede have silicate mantles; Io's ~ silicate mantle is overlain by a volcanic crust, Ganymede's ~ thick silicate mantle is overlain by ~ of ice, and Europa's ~ km silicate mantle is overlain by ~ of ice and possibly liquid water. The silicate mantle of the Earth's moon is approximately 1300–1400 km thick, and is the source of mare basalts. The lunar mantle might be exposed in the South Pole-Aitken basin or the Crisium basin. The lunar mantle contains a seismic discontinuity at ~ depth, most likely related to a change in composition.

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fiction ...

and Triton each have a mantle made of

or other solid volatile substances.

Asteroids with mantles

Some of the largest

have mantles; for example, Vesta has a silicate mantle similar in composition to

diogenite Diogenites are a group of the HED meteorite clan, a type of achondritic stony meteorites. Origin and composition Diogenites are currently believed to originate from deep within the crust of the asteroid 4 Vesta, and as such are part of the HE ...

meteorites.

References

External links

The Biggest Dig: Japan builds a ship to drill to the earth's mantle
– Scientific American (September 2005)
Information on the Mohole Project
{{DEFAULTSORT:Mantle (Geology) Structure of the Earth Planetary geology