Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 11 April 2008:
Vol. 320. no. 5873, pp. 214 - 218
DOI: 10.1126/science.1152860
Prev | Table of Contents | Next

Reports

Determining Chondritic Impactor Size from the Marine Osmium Isotope Record

François S. Paquay,1* Gregory E. Ravizza,1 Tarun K. Dalai,1{dagger} Bernhard Peucker-Ehrenbrink2

Decreases in the seawater 187Os/188Os ratio caused by the impact of a chondritic meteorite are indicative of projectile size, if the soluble fraction of osmium carried by the impacting body is known. Resulting diameter estimates of the Late Eocene and Cretaceous/Paleogene projectiles are within 50% of independent estimates derived from iridium data, assuming total vaporization and dissolution of osmium in seawater. The variations of 187Os/188Os and Os/Ir across the Late Eocene impact-event horizon support the main assumptions required to estimate the projectile diameter. Chondritic impacts as small as 2 kilometers in diameter should produce observable excursions in the marine osmium isotope record, suggesting that previously unrecognized impact events can be identified by this method.

1 Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822–2225, USA.
2 Department of Marine Chemistry and Geochemistry, Woods Hole Oceano-graphic Institution, Woods Hole, MA 02543, USA.

{dagger} Present address: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India.

* To whom correspondence should be addressed. E-mail: paquay{at}hawaii.edu

Read the Full Text


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Comment on "Determining Chondritic Impactor Size from the Marine Osmium Isotope Record".
J. V. Morgan (2008)
Science 321, 1158a
   Abstract »    Full Text »    PDF »
Response to Comment on "Determining Chondritic Impactor Size from the Marine Osmium Isotope Record".
F. S. Paquay, G. E. Ravizza, T. K. Dalai, and B. Peucker-Ehrenbrink (2008)
Science 321, 1158b
   Abstract »    Full Text »    PDF »
Applications of PGE Radioisotope Systems in Geo- and Cosmochemistry.
R. W. Carlson, S. B. Shirey, and M. Schonbachler (2008)
Elements 4, 239-245
   Abstract »    Full Text »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)