chondrites

Chondrites are a class of stony meteorites distinguished by the presence of chondrules, small round grains of silicate that formed as droplets in the early solar nebula and were incorporated into the meteorite’s parent body without complete melting. They are among the oldest materials in the solar system, dating to about 4.56 billion years ago, and are considered primitive because most have not undergone extensive igneous differentiation.

Chondrites are divided into three broad groups: carbonaceous chondrites, ordinary chondrites, and enstatite chondrites. Carbonaceous varieties (including CI, CM, CO, CV, CR, CH, CB) are rich in water-bearing minerals and organic compounds. Enstatite chondrites (EH and EL) formed in highly reduced, low-oxygen environments. Ordinary chondrites (H, L, LL) are the most common class and show a mix of metal and silicate phases. Chondrules, matrix, and sometimes calcium-aluminum-rich inclusions are characteristic components of these meteorites.

In addition to chondrules, chondrites contain a fine-grained matrix; carbonaceous types frequently preserve abundant volatile-rich materials and organic matter. Many chondrites also host CAIs, among the oldest solid constituents found in the solar system. The degree of thermal metamorphism and aqueous alteration is described by petrologic types, typically ranging from 3 (least altered) to 6 (more altered).

Chondrites are central to cosmochemistry and planetary science because they preserve primitive solar-system material. They provide insights into chondrule formation, nebular chemistry, isotopic distributions, and the early processes that shaped planetary building blocks. They are the most widespread type of meteorite recovered on Earth.