-
Blocage de la polyspermie chez les Mammifères
Le blocage de la polyspermie chez les Mammifères fait débat depuis longtemps. Si la réaction corticale est clairement un des moyens, le fait qu’elle se produise « tardivement » après l’entrée du spermatozoïde compte pour blocage mais pas comme blocage précoce. Certains mettent en avant une dépolarisation de la membrane de l’ovocyte mais cette conclusion est loin…
-
La comète Ison
La comète Ison découverte en 2012 par deux astronomes amateurs est passée toute proche du Soleil mais les images de la NASA laisse penser qu’elle pourrait avoir survécu à son passage alors qu’encore hier, on ne le pensait pas. En fait, seul une partie du noyau de la comète serait encore intact. Espérons qu’il sera…
-
Le polymorphisme du carbone dans les météorites choquées : découverte de forme ultra-dures, plus dures que le diamant
-
Carbon polymorphism in shocked meteorites: Evidence for new natural ultrahard phases (our EPSL paper)
We published a paper entitled « Carbon polymorphism in shocked meteorites: Evidence for new natural ultrahard phases » in the recent issue of EPSL. This post is the uncorrected proof featuring all the references, tables and pictures we published in the paper. Comments are very welcome. If you want a reprint of the paper, please use thee…
-
Mineralogy and Petrology of Comet 81P/Wild 2 Nucleus Samples
NEW PUBLICATION IN SCIENCE The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca…
-
Comet 81P/Wild 2 Under a Microscope
NEW PUBLICATION IN SCIENCE The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an…
-
Equation of state and phase transition in KAlSi3O8 hollandite at high pressure
NEW PUBLICATION IN AMERICAN MINERALOGIST The tetragonal hollandite structure (KAlSi3O8 hollandite) has been studied up to 32 GPa at room temperature using high-pressure in-situ X-ray diffraction techniques. A phase transformation from tetragonal I4/m phase to a new phase was found to occur at about 20 GPa. This transition is reversible on release of pressure without…
-
A new high-pressure form of KAlSi3O8 under lower mantle conditions
NEW PUBLICATION In situ X-ray diffraction measurements have been made on KAlSi3O8 hollandite using diamond anvil cell and multianvil apparatus combined with synchrotron radiation. Both of the measurements with different techniques demonstrated that K-hollandite transforms to a new highpressure phase (hollandite II) at 22 GPa upon increasing pressure at room temperature. The X-ray diffraction peaks…