Center for Meteorite Studies

The ASU Center for Meteorite Studies is pleased to announce that François Tissot, a graduate student at the University of Chicago, is the recipient of the 2015 Nininger Meteorite Award.

Francois TissotFrançois’s paper “Origin of uranium isotope variations in early solar nebula condensates” describes how the characterization of the U isotope composition of 12 fine-grained Calcium and Aluminum-rich Inclusions (CAIs: The earliest solids to form in the Solar System) demonstrates that the decay of Curium-247 is the main process responsible for the variability of the 238U/235U ratios of CAIs.

The discovery in the late 2000s that the 238U/235U ratios of meteoritic materials varied by up to several permil, meant that previously published Pb-Pb ages of CAIs (and thus of the Solar System) were unreliable. The cause of this variability has been heavily debated; some argued that it was due to 247Cm decay, while others preferred scenarios that invoked fractionation upon condensation. Despite numerous attempts since the late 1970s, until now, no study has been able to unambiguously show that 247Cm was alive in the early Solar System and could be responsible for the variable U isotope composition in CAIs.

By studying fine-grained CAIs depleted in U and potentially enriched in Cm, François and his co-workers were able to resolve excesses of 235U due to 247Cm decay reaching ~+6% relative to average Solar System composition. Combined with modeling of the chemical evolution of the galaxy, the early Solar System abundance of 247Cm points to a universality of the r-process of nucleosynthesis, provided that Hafnium-182 has an s-process origin. Multiple r-process sites have been considered in the past but may only be relevant to exotic conditions prevailing in the earliest generation of stars of the Galaxy.


Category: CMS News

Comments are closed.

Facebook
Twitter
YouTube

Sign Up for Center Updates!

Be the first to learn about CMS events and news; sign up for email updates here!


Postdoctoral Scholar Opportunities!

The Center for Meteorite Studies at Arizona State University invites applications for 2 Postdoctoral Research Associates.  Click here for details!




Meteorite of the Month

Moss

July’s Meteorite of the Month is Moss, a CO3.6 carbonaceous chondrite that fell the morning of July 14, 2006, in Østfold, Norway. According to the Meteoritical Bulletin (MB 91): At …


Upcoming Events

July 2017
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
June 25, 2017 June 26, 2017 June 27, 2017 June 28, 2017 June 29, 2017 June 30, 2017 July 1, 2017
July 2, 2017 July 3, 2017 July 4, 2017 July 5, 2017 July 6, 2017 July 7, 2017 July 8, 2017
July 9, 2017 July 10, 2017 July 11, 2017 July 12, 2017 July 13, 2017 July 14, 2017 July 15, 2017
July 16, 2017 July 17, 2017 July 18, 2017 July 19, 2017 July 20, 2017 July 21, 2017 July 22, 2017
July 23, 2017 July 24, 2017 July 25, 2017 July 26, 2017 July 27, 2017 July 28, 2017 July 29, 2017
July 30, 2017 July 31, 2017 August 1, 2017 August 2, 2017 August 3, 2017 August 4, 2017 August 5, 2017