Primitive Terrestrial Xenon: A Relation to Refined Composition of Solar Wind

To explain the isotopic structure of terrestrial Xe, a hypothetical U-Xe (unrelated to uranium) was mathematically constructed using multidimensional correlation diagrams of stepwise heating data of carbonaceous chondrites [1]. The composition of U-Xe was derived without any references to solar Xe. Nevertheless U-Xe turned out to be almost identical to Solar Wind (SW) except for two heaviest isotopes ^(136)Xe and ^(134)Xe, in which U-Xe was depleted. The mismatch in these two heaviest Xe isotopes was attributed to either the presence of nearly pure Xe-H (heavy branch of Xe-HL) in the Sun or to deficit of Xe-H in the carbonaceous chondrites from which U-Xe composition has been de-rived. There are two difficulties in this approach: U-Xe has never been reproducibly observed and Xe-H and Xe-L are apparently inseparable

Evidence of presolar SiC in the Allende Curious Marie calcium–aluminium-rich inclusion

Calcium–aluminium-rich inclusions (CAIs) are one of the first solids to have condensed in the solar nebula, while presolar grains formed in various evolved stellar environments. It is generally accepted that CAIs formed close to the Sun at temperatures above 1,500 K, where presolar grains could not survive, and were then transported to other regions of the nebula where the accretion of planetesimals took place. In this context, a commonly held view is that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. Here we demonstrate, on the basis of noble gas isotopic signatures, that presolar SiC grains were incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent-body processing. This finding provides new clues on the conditions in the nascent Solar System at the condensation of the first solids

I-Xe studies of aqueous alteration in the Allende CAI Curious Marie

The Allende fine-grained inclusion Curious Marie is a unique CAI. It is depleted in uranium but contains large ^(235)U excess [1], providing new evidence that ^(247)Cm was alive in the Early Solar System, as has been previously suggested [2], and leading to an updated (^(247)Cm/^(235)U)initial ratio of (1.1±0.3)×10^(-4)

Weak decay of 130 Ba and 132 Ba : Geochemical measurements

The half-life of 130Ba due to multichannel weak decay (2β+, 2EC, and ECβ+) has been determined for the first time by the measurement of the 130Xe daughter accumulated in natural barite (BaSO4) from the Belorechenskoe deposit in North Caucasus, Russia. The accumulation time was determined from U-Xe and K-Ar gas-retention ages measured in the same material, yielding a half-life for 130Ba for all weak decay modes of 2.2±0.5×1021yr (68% C.L.), about a factor of 2 lower than that predicted by the proton-neutron quasiparticle random phase approximation. From excess 132Xe observed in this barite, the half-life for weak decay of 132Ba can be estimated (T1/2=1.3±0.9×1021yr). However, this value is more tentative, since other sources of this isotope cannot be excluded, but the lower limit of 2.2×1021yr remains firm

I-Xe studies of aqueous alteration in the Allende CAI Curious Marie

The Allende fine-grained inclusion Curious Marie is a unique CAI. It is depleted in uranium but contains large ^(235)U excess [1], providing new evidence that ^(247)Cm was alive in the Early Solar System, as has been previously suggested [2], and leading to an updated (^(247)Cm/^(235)U)initial ratio of (1.1±0.3)×10^(-4)

Solar Wind Krypton in Genesis Collectors and in Lunar Regolith: Why are they Different?

Compared to Xe, Kr demonstrates the smallest isotopic variations among solar system components. At the same time Kr is more sensitive to terrestrial contamination since atmospheric ^(84)Kr/^(132)Xe = 27.7 is the highest among all known solar and presolar components. Therefore higher precision isotopic analyses, and careful control of contamination, are needed to make\ud accurate determinations of Kr isotopic compositions of various solar system components

Light noble gas composition of different solar wind regimes: results from genesis

The Genesis mission provided samples of solar wind (SW) from different regions on the Sun. These SW regime samples are important in understanding fractionation processes upon formation and acceleration of the SW to ultimately deduce solar composition from SW values. We present He and Ne isotopic and elemental compositions of the bulk SW (SW of entire collection period) and the 3 major SW regimes: slow (from the ecliptic plane, emanating from above streamers), fast (emanating from coronal holes), and coronal mass ejections (CME). At the conference we will also present Ar data

First Analysis of All Xenon Isotopes in Genesis Solar Wind AloS Collector

Recently we made successful measurements of all solar wind (SW) krypton isotopes in Genesis Al-collectors [1]. Here we report results of 20 independent analysis of Xe extracted from Aluminum on Sapphire (AloS) under four different experimental conditions