Abstract
Geochemistry![Figure][1] CREDIT: NASA/JPL-CALTECH/O. KRAUSE/STEWARD OBSERVATORY Primitive meteorites contain grains of materials that predate the formation of the solar system. These materials—which include, among others, diamond, graphite, and various oxides and silicates—were present in the molecular cloud from which the Sun and the solar system formed and were later incorporated into primitive solar system solids. Presolar grains are identified by their unusual isotopic compositions, which can only be explained if they formed outside the solar system, in the outflows or explosions of other stars. Using nano secondary ion mass spectrometry (NanoSIMS) and Auger electron spectroscopy, Haenecour et al. report the identification of two silica (SiO2) grains in the primitive meteorites LaPaz 031117 and Grove Mountains 021710. The oxygen isotopic composition of these two grains is different from those of previously identified presolar SiO2 grains, and it indicates that the two grains originated from core collapse supernovae: the thermonuclear explosions that end the lives of stars heavier than eight times the mass of the Sun. The presence of SiO2 dust in matter ejected by such explosions was predicted by theoretical models; recent observations by NASA's Spitzer Space telescope have also suggested their presence in supernova remnants. Astrophys. J. 768 , L17 (2013). [1]: pending:yes
Highlights
The conversion of tropical forest to oil palm plantations has rapidly increased over the past decade, predominantly in Southeast Asia, where such cultivation dominates over 2 million hectares
Raptors were more abundant in plantations than in logged forest, whereas the reverse was true for insectivores and granivores
Functional diversity was similar between logged and primary forest but greatly reduced in plantations, with just a few generalist species filling a wide range of functional roles
Summary
Primitive meteorites contain grains of materials that predate the formation of the solar system. These materials—which include, among others, diamond, graphite, and various oxides and silicates—were present in the molecular cloud from which the Sun and the solar system formed and were later incorporated into primitive solar system solids. Presolar grains are identified by their unusual isotopic compositions, which can only be explained if they formed outside the solar system, in the outflows or explosions of other stars. The oxygen isotopic composition of these two grains is different from those of previously identified presolar SiO2 grains, and it indicates that the two grains originated from core collapse supernovae: the thermonuclear explosions that end the lives of stars heavier than eight times the mass of the Sun. The presence of SiO2 dust in matter ejected by such explosions was predicted by theoretical models; recent observations by NASA’s Spitzer Space telescope have suggested their presence in supernova remnants.
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