Autor Thema: Verbesserte Datierungsmethode für Carbonate in CM-Chondriten vorgestellt  (Gelesen 571 mal)

Offline karmaka

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Verbesserte Datierungsmethode für Carbonate in CM-Chondriten vorgestellt

Zur Klärung der Frage wann im frühen Sonnensystem zum ersten Mal flüssiges Wasser auftrat, wurde eine verbesserte Methode zur Datierung der Carbonat-Körnchen in kohligen Chondriten entwickelt.

Diese liefert ein Alter von ~ 4,5634 Milliarden Jahren für die Carbonate in kohligen Chondriten.

http://www.s.u-tokyo.ac.jp/en/press/2012/02.html

Evidence for the late formation of hydrous asteroids from young meteoritic carbonates

Wataru Fujiya, Naoji Sugiura, Hideyuki Hotta, Koji Ichimura, Yuji Sano

Nature Communications, Published online on 17 January 2012.

http://www.nature.com/ncomms/journal/v3/n1/full/ncomms1635.html#/abstract

Untersuchte Meteoriten:     Murchison, Yamato 791198, Allan Hills 83100 und Sayama

Zitat
The accretion of small bodies in the Solar System is a fundamental process that was followed by planet formation. Chronological information of meteorites can constrain when asteroids formed. Secondary carbonates show extremely old 53Mn–53Cr radiometric ages, indicating that some hydrous asteroids accreted rapidly. However, previous studies have failed to define accurate Mn/Cr ratios; hence, these old ages could be artefacts. Here we develop a new method for accurate Mn/Cr determination, and report a reliable age of 4,563.4+0.4/−0.5 million years ago for carbonates in carbonaceous chondrites. We find that these carbonates have identical ages, which are younger than those previously estimated. This result suggests the late onset of aqueous activities in the Solar System. The young carbonate age cannot be explained if the parent asteroid accreted within 3 million years after the birth of the Solar System. Thus, we conclude that hydrous asteroids accreted later than differentiated and metamorphosed asteroids.

Grafik: http://www.s.u-tokyo.ac.jp/en/press/2012/images/02/02-b.jpg

Zitat
Comparison of carbonate ages in this study with those in previous studies. Previous studies reported ages older than the age of the Solar System (dotted circles). In this study, we demonstrated that they should be revised and converge on 4563.4 million years ago.

 :hut:

Martin

 

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