Calcium–aluminium-rich inclusion

Calcium - aluminum - rich inclusions (abbreviated " CAI " from engl. Ca -Al -rich inclusions ) are micrometer - to centimeter-sized light-colored inclusions, which in some meteorites, called carbonaceous chondrites, occur. In addition, CAI -like fragments were found in samples of comet Wild 2, which brought the Stardust probe in early 2006 to Earth. CAI consist of calcium-and aluminum-containing minerals, and are among the first minerals that even at relatively high temperatures ( up to 2000 Kelvin) from which cooling protoplanetary nebula from which the solar system was formed, condensed.

Means uranium - lead dating could be established for them an age of 4567.2 ± 0.6 million years, which can be interpreted as the beginning of formation of our planetary system. The measured lead ratios lie within the error tolerances on the so-called Konkordia, a theoretical curve which is used to determine the reliability of the measured lead and lead - aging. Age can therefore be regarded as secured very well. Nevertheless, it was argued that the error tolerances of the isotope measurements, a very slight disturbance of the uranium-lead isotopic system in CAIs permitted, providing for an age would represent only a lower limit of the actual age, which in reality is a bit higher. Other, based on manganese -chromium and magnesium - aluminum - dating methods were actually a slightly older age with a value of 4,571 million years.

Credentials

• Meteorite