1,850 research outputs found
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How Useful are High-Precision Delta ?17O Data in Defining the Asteroidal Sources of Meteorites?: Evidence from Main-Group Pallasites, Primitive and Differentiated Achondrites
High-precision oxygen isotope analysis is capable of revealing important information about the relationship between different meteorite groups. New data confirm that the main-group pallasites are from a distinct source to either the HEDs or mesosiderites
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Laser ablation of Diamond and Genesis concentrator target material
UV laser ablations of CVD diamond using two wavelengths of radiation (266 nm and 213 nm) have been compared. The impetus for this work is the 2004 return of Genesis and extraction of solar-wind oxygen implanted in diamond
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Understanding the Chlorine Isotopic Compositions of Apatites in Lunar Basalts
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Oxygen Isotopic Constraints on the Number and Origin of Basaltic Achondrite Parent Bodies
Our data show that HED meteorites have a homogeneous oxygen isotopic composition consistent with a magma ocean on Vesta. Ibitira, Asuka 881394, Pasamonte, and NWA 1240 probably come from separate parent asteroids
Approximations of Sobolev norms in Carnot groups
This paper deals with a notion of Sobolev space introduced by
J.Bourgain, H.Brezis and P.Mironescu by means of a seminorm involving local
averages of finite differences. This seminorm was subsequently used by A.Ponce
to obtain a Poincar\'e-type inequality. The main results that we present are a
generalization of these two works to a non-Euclidean setting, namely that of
Carnot groups. We show that the seminorm expressd in terms of the intrinsic
distance is equivalent to the norm of the intrinsic gradient, and provide
a Poincar\'e-type inequality on Carnot groups by means of a constructive
approach which relies on one-dimensional estimates. Self-improving properties
are also studied for some cases of interest
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Characterization of mesostasis areas in mare basalts: constraining melt compositions from which apatite crystallizes
Crystallization of major silicate and oxide phases from basaltic melts produces late-stage liquids whose chemical compositions differ from the initial melt. These chemically evolved liquids crystallize phases in the interstitial mesostasis regions in lunar basaltic rocks. Enrichment of incompatible elements, including volatiles such as OH, F, Cl, is characteristic of these late-stage liquids and encourages growth of accessory phases including apatite [Ca5(PO4)2(F,Cl,OH)]. Apatite is the main volatile bearing crystalline phase in lunar rocks. It starts crystallizing after ~95% melt solidification in typical mare basalts, but could crystallize earlier, after ~85-90% solidification in KREEP basalts. Using the OH contents of apatites, several researchers have calculated water contents for parental magmas. These calculated parental magma water contents can then be used to estimate a range of values for water in the mantle source regions of mare basalts [e.g.,2-6]. Therefore, a better characterization of the mesostasis areas, and of the melts in which apatite forms, is paramount to gain further insights and constraints on water in the lunar interior, especially because important parameters such as partitioning of volatiles between late-stage melts and apatite remain poorly constrained
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