Delving into Allende's dark secrets

What are the strange dark clasts within carbonaceous chondrites? How did they form? And what do they tell us about the early solar system? Mark Sephton, one of a team investigating the Allende meteorite, summarizes their findings. Asteroids are remnants of the planetary construction process that occurred in the early solar system. By studying asteroids and their collision-induced fragments that fall to Earth as meteorites, we approach an understanding of the physical and chemical mechanisms that marked nascent planet formation. It is in the oldest meteorites that a record of events that began the journey from nebula material to planet-sized bodies is contained. Consequently, much attention is directed towards the most ancient class of meteorite: carbonaceous chondrites. These meteorites contain a diverse mixture of mineralogical components including high-temperature silicate “chondrules”, formed by rapid heating then cooling, but also low-temperature materials such as carbonates and phylosilicates, which are generally considered to be evidence of liquid water on the meteorite parent body. Yet the role of water and heat in the generation of other components remains enigmatic.