Ca-Al-rich inclusions (CAIs) are centimeter-sized light-coloured calcium and aluminium rich inclusions found in carbonaceous chondrites. CAIs consists of high temperature minerals and are among the first solids which condensed from the cooling protoplanetary disk. CAI's were formed at much higher temperatures than the associated chondrules, and may have survived many high-temperature events, whereas most chondrules are the product of a single transient melting event.

The isotopic anomaly of CAI's give us valuable clues about our solar system's formation, suggesting that the solar nebula collapsed shortly after a nearby supernova, Radiometric dating shows that the CAI's formed about 2 million years before the chondrules formed.

Using lead 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.

Therefore, CAI's are a trail from a supernova to "us" (humans) via dust.

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.
• Krot, A. N. (Sept., 2002) Dating the Earliest Solids in our Solar System. Planetary Science Research Discoveries. http://www.psrd.hawaii.edu/Sept02/isotopicAges.html
• 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

Meteorites | Kalzium-Aluminium-reiche Einschlüsse