Structure and thermal history of the H-chondrite parent asteroid revealed by thermochronometry.

Our Solar System formed approximately 4.6 billion years ago from the collapse of a dense core inside an interstellar molecular cloud. The subsequent formation of solid bodies took place rapidly.

Niobium-zirconium chronometry and early solar system development.

Niobium-92 (92Nb) decays to zirconium-92 (92Zr) with a half-life of 36 million years and can be used to place constraints on the site of p-process nucleosynthesis and the timing of early solar system processes. Recent results have suggested that the initial 92Nb/93Nb of the solar system was high (>10(-3)). We report Nb-Zr internal isochrons for the ordinary chondrite Estacado (H6) and a clast of the mesosiderite Vaca Muerta, both of which define an initial 92Nb/93Nb ratio of approximately 10(-5).