Jan 25 2008
From The Space Library
A team of scientists led by Hope A. Ishii and John P. Bradley of the Lawrence Livermore National Laboratory announced in the journal Science that material they had analyzed from the comet Wild 2 more closely resembled the material composition of an asteroid than they had expected. Using Livermore’s scanning transmission electron microscope SuperSTEM, the scientists had assessed a sample of the comet’s tail—NASA’s Stardust craft had gathered the sample in 2004. Scientists had long thought that primitive outer nebula material composed comets, so the Livermore team had expected to find an abundance of that material. However, they had found very little primitive outer nebula material, instead finding larger-than-expected quantities of the newer, inner solar nebula matter common in asteroids. The researchers pointed out that this surprising discovery emphasized that asteroids and comets do not comprise distinctly different entities but, instead, exist along a continuum in regard to their material composition.
John Johnson Jr., “NASA’s Stardust Upends Comet Theory,” Los Angeles Times, 25 January 2008; see also Hope A. Ishii et al., “Comparison of Comet 81P/Wild 2 Dust with Interplanetary Dust from Comets,” Science 319, no. 5862 (25 January 2008): 447-450.
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