Ca-Al-rich inclusions

Ca-Al-rich inclusions (CAIs) are centimeter sized light-coloured inclusions found in carbonaceous chondrites. CAIs consists of hightemperature minerals and are among the first solids which condensed from the cooling protoplanetary disk. Using Pb isotopic data determined on CAIs an age of 4567.2±0.6 million years can be calculated which can be interpreted as the beginning of the formation of the planetary system. However, due to possible disturbations of the Pb isotopic system within the CAIs this age is possibly only a lower limit of the true age. Also an age of 4571 Ma for CAIs has been given, based on Mn-Cr and Mg-Al isotopic data.

Further reading

• Gilmour J. (2002) The Solar System's First Clocks Science 297, 1658-1659.
• Amelin Y., Krot A. N., Hutcheon E. D., and Ulyanov A. A. (2002) Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions Science, 297, 1678-1683.
• NASA Planetary Science Research Discoveries: Dating the Earliest Solids in our Solar System
• Shukolyukov A., Lugmair G.W. (2002) Chronology of Asteroid Accretion and Differentiation 687-695, in Asterois III, Bottke W.F., Cellino A., Paolicchi P., Binzel R.P., eds., University of Arizona Press (2002), ISBN: 0816522812