A mantle is a layer inside a planetary body bounded below by a

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...

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 opaqu ...

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. Mathematical ...

. All terrestrial planets (including

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

), a number of asteroids, 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 Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 1024 kg and thus makes up 67% of the mass of Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly so ...

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 The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...

it behaves as a viscous fluid. Partial melting of the mantle at mid-ocean ridges 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 Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the soli ...

of the mantle at subduction zones 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 A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a percen ...

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 South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz ...

or the Crisium basin. The lunar mantle contains a seismic discontinuity at ~ depth, most likely related to a change in composition. Titan and Triton each have a mantle made of

or other solid volatile substances.

Asteroids with mantles

Some of the largest asteroids 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 HED m ...

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