Primitive Meteorite Contains Cometary Surprise

Comets, and some primitive asteroids, preserve the microscopic remnants of the basic building blocks of rocky bodies in our solar system. Analyzing these building blocks can provide important clues both to the source of the water for Earths’ oceans and to the inventory of organic matter delivered to the early Earth. In general, samples from comets preserve a greater abundance of organic matter and primordial presolar dust grains from the protosolar molecular cloud, and generations of stars older than the sun, than do samples from asteroids. Meteorites, which come from asteroids, generally have less organic matter and preserve fewer presolar grains. This is because asteroids and comets formed at different places in the solar nebula, and, thus sampled different distributions of organic and mineral components. Furthermore, the warmer conditions on asteroids allowed for liquid water and greater subsequent physical and chemical alteration of the accreted material.

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