Carbonaceous chondrites are a rare and scientifically important group of stone meteorites. As Buseck and Hua stated so intriguingly in their 1993 paper: “They are nebular leftovers and thus invaluable recorders of some of the oldest and best kept secrets … of the solar system.” In other words, carbonaceous chondrite meteorites carry within them the last traces — sometimes in the form of tiny diamonds — of extremely ancient and long-vanished suns or planets that pre-dated our own solar system. As such, carbonaceous chondrite meteorites contain the oldest materials that any human has ever encountered.
Carbonaceous chondrites are divided into several subclasses, including CI, CV, CM, CR, CH, CB, CK, and CO.
The multiple subclasses are due, in part, to carbonaceous chondrites having formed on a variety of different types of asteroids. Some, such as the CM group, are largely “undifferentiated,” meaning their compositions have been little changed since the formation of the solar system over 4.6 billion years ago; others appear to have been altered by heat or water.
Many carbonaceous chondrites contain significant amounts of water, carbon, organic compounds and in some cases, extraterrestrial amino acids. This has led to scientific speculation that — during our planet’s distant past — they may have brought from space, the materials that were needed for life to evolve here on Earth.