Glossaire beginning with M

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Magnetosphere

Upper region of the upper atmosphere, characterized by relatively high-energy, charged particles trapped in the Earth's magnetic field. Jupiter and Saturn also have a magnetosphere.

Meridian (celestial)
Great circle passing through the two celestial poles.
Meteorite
Solid body belonging to the Solar system, which can sometimes fall on the Earth. Meteorites are very primitive rocks; the carbonaceous chondrites are the most interesting ones to understand the formation of the Solar system.
Molecule
Assembly of several atoms.