Primitive chondritic meteorites contain up to ∼1500 ppm of nanometersized diamonds. These nanodiamonds contain isotopically anomalous noble gases, nitrogen, hydrogen, and other elements. The isotopic anomalies indicate that meteoritic nanodiamonds probably formed outside our solar system, prior to the Sun's formation (they are thus presolar grains), and they carry within them a record of nucleosynthesis in the galaxy. Their characteristics also reflect the conditions encountered in interstellar space, in the solar nebula, and in the host meteorites.

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