Gathering Stardust

StarDate: January 23, 2009

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The basic concept of how the newly forming solar system was laid out sounds like a well-organized kitchen: hot dishes in the oven, cold dishes in the freezer, and in-between ones on the counter. But some grains of comet dust are telling us that things may not have been quite so tidy. It's as if someone threw a lot of those courses into a blender and turned it on "puree."

Earth and the other planets of the solar system coalesced from a disk of gas and solid particles of ice or rock around the newborn Sun. The ices were confined to the cold outer regions of the solar system, where they formed comets -- "dirty snowballs" that sprout long tails when they get close to the Sun.

Five years ago this month, the Stardust spacecraft flew through the tail of Comet Wild 2, where it was pelted by dust. It captured some of these tiny grains and brought them back to Earth two years later.

A detailed analysis shows that the grains didn't all form in the cold outer solar system, where Wild 2 itself was born. Instead, there was a mixture of particles from across the solar system. Some did come from the outer solar system, but others came from the hot inner regions, or from the more moderate climes around today's asteroid belt.

The findings suggest that the early solar system was dynamic. Solid particles from close to the Sun were hurled into the fringes of the solar system -- where they could join the list of ingredients in icy comets.

Script by Damond Benningfield, Copyright 2008

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