[IGPP Everyone] Baecker Geocheminar

[John Wasson]

Geocheminar

Slichter 3843

12 noon, 3 Mar 2015

Bastian Baecker

EPSS

Noble gases in micrometeorites from Antarctica

The bulk of extraterrestrial matter collected by Earth is in the form of micrometeorites (MMs), which have their peak flux onto Earth at about 200-230 μm in diameter. Petrographic and geochemical data indicate that most small micrometeorites are related to CM and CI chondrites. Recent studies suggest that most larger MMs (>300 µm) derive from ordinary chondrites. MMs may have made - and still make - important contributions to the volatile inventory of the Earth. I surveyed noble gas contents (He through Xe) and characterized the petrography of micrometeorites. Previous research showed that He and Ne isotopes are similar to those of the solar wind. However, the inventory of heavy primordial noble gases was largely uncharacterized. In particular, useful data were lacking on the potentially diagnostic isotopic composition of Xe. We therefore studied Xe as well as light rare gases using a high sensitivity "Noblesse" mass spectrometer. The study makes a first-step towards understanding of some aspects of the formation of the solar system and in particular the terrestrial atmosphere. My first results were obtained on “large” micrometeorites from Victoria Land, Transantarctic Mountains, in the Miller Butte “micrometeorite traps”. My second sample set includes the tiny “fresh” MMs from the snow of Dome C (20-120 μm).

 

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