Science Daily
Scientists are tracking the violent convulsions in the giant cloud of gas and dust that gave birth to the solar system 4.5 billion years ago via a few tiny particles from comet Wild 2.
These convulsions flung primordial material billions of miles from the hot, inner regions of the gas cloud that later collapsed to form the sun, out into the cold, nether regions of the solar system, where they became incorporated into an icy comet.
"If you take a gas of solar composition and let it cool down, the very first minerals to solidify are calcium and aluminum-rich," said Steven Simon, Senior Research Associate in Geophysical Sciences at the University of Chicago. And comet Wild 2 does contain these and other minerals formed at high temperatures. "That's an indication of transport from the inner solar system to the outer solar system, where comets are thought to have formed," he said.
Simon presents his data in the November 2008 issue (expected to be published early next year) of Meteoritics and Planetary Science. His 11 co-authors include Lawrence Grossman, Professor in Geophysical Sciences at the University of Chicago.
Either turbulence within the nebula, or a phenomenon called bipolar outflow from the early sun could account for the long-distance transport of cometary material, according to Simon and his Meteoritics co-authors.
Bipolar outflow results when the rotating disks that surround developing new stars jet gas from their polar regions, which astronomers have observed telescopically. "That's part of the so-called X-wind model, which is somewhat controversial," Simon said.
The controversial aspect of the X-wind model is the claim that the process would produce the kind of granules that Simon and his colleagues have now identified in comet Wild 2. Another less likely possibility: The cometary material in question may have formed around another star of composition similar to the sun, then drifted into the outer reaches of the solar system. There it became incorporated into comet Wild 2.
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