Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.v43j..03i&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #V43J-03
Physics
[1028] Geochemistry / Composition Of Meteorites, [1041] Geochemistry / Stable Isotope Geochemistry, [3694] Mineralogy And Petrology / Instruments And Techniques
Scientific paper
The discovery of oxygen isotope anomalies changed forever our picture of the early solar system: Allende refractory inclusions were found to have a 4% excess in 16O relative to terrestrial. While originally ascribed to nucleosynthetic addition, these anomalies appear to be best explained by a chemical fractionation mechanism, either a symmetry effect (as in the Earth atmosphere ozone), or photodissociation and self-shielding of CO. Ion microprobe analysis has expanded the range in oxygen isotopes in early solar system materials dramatically over recent years. Ion microprobes can select small areas, but also have an advantage of depth resolution over scales of nanometres such that specific sites can be targeted. Apparent 16O anomalies range from +8% excess relative to terrestrial oxygen in the a006 chondrule (Acfer 214) to a -17% 16O deficit in an Fe-rich phase in matrix of the Acfer 094 carbonaceous chondrite. The main reservoirs of oxygen appear to be the planetary composition (near terrestrial) and refractory inclusion oxygen (4% 16O excess). Both of these compositions have a basis to be coincident with the oxygen isotopic composition of the Sun. However, following analysis of the Genesis samples the composition of solar oxygen appears consistent with an oxygen composition enriched in 16O. This appears to show a dichotomy in solar system oxygen isotope compositions with the solid bodies of the solar system differing from the bulk. Such a situation is probably consistent with the Sun reflecting the bulk of its oxygen coming from 16O-enriched CO while refractory silicates and oxides have compositions near terrestrial. Processing in the solar system from the 16O-enriched composition of the Sun to the 17O, 18O enriched terrestrial composition appears unlikely based on the amount of material to be processed, the uniformity of compositions, and the time frame involved. Refractory inclusions may have started their existence with different or even diverse starting compositions, but during heating close to the Sun equilibrated with the solar composition. Chondrules only show partial equilibration with solar oxygen. The role of the isotopically heavy reservoirs, such as preserved in lunar soils and meteorite matrices needs to be resolved.
No associations
LandOfFree
Oxygen Isotope Distribution in the Early Solar System: An Ion Microscopic View of a Big Issue does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Oxygen Isotope Distribution in the Early Solar System: An Ion Microscopic View of a Big Issue, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxygen Isotope Distribution in the Early Solar System: An Ion Microscopic View of a Big Issue will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1776346