Meteoriten

Meteoriten, or meteorites in English, are solid fragments from space that survive passage through Earth’s atmosphere and reach the planet’s surface. They originate mainly from asteroids in the inner solar system, but some are derived from the Moon or Mars, or from comets. Before reaching the ground they are called meteoroids, and during atmospheric entry they are observed as meteors or fireballs; if they land, they are meteorites.

Classification and composition form the basis of most meteorite study. Meteorites are commonly grouped into three broad classes by their bulk chemistry and mineralogy: irons, stones, and stony-irons. Iron meteorites consist predominantly of nickel–iron metal and are usually associated with melted parent bodies. Stone meteorites are silicate-rich and subdivide into chondrites, which contain chondrules and represent primitive solar system material, and achondrites, which have undergone melting and differentiation. Stony-iron meteorites are mixtures of metal and silicates and include pallasites and other mixed types.

Chondrites are the most abundant and important for understanding early solar system processes. Chondrules are small, rounded silicate grains formed as molten droplets in the early solar nebula. Achondrites reflect crustal or mantle material from differentiated bodies. A portion of meteorites are known to originate from the Moon or Mars, providing direct samples of other worlds.

Meteorites are study subjects for dating, isotopic compositions, mineralogy, and organic chemistry. They offer insights into planetary formation, the dating of the solar system to about 4.5 billion years ago, and the distribution of water and organic compounds in the early solar system. Notable examples include Allende, Murchison, and iron meteorites such as the Hoba specimen.