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Melted Crumbs from Asteroid Vesta

Mercury Winter 2008 Table of Contents


spherule

In this scanning electron microscope image of spherule SP37-3, the plagioclase feldspar grain is labeled "Pg."
Image courtesy of Jeremy Delaney et al, 2004 LPSC poster

by Linda M.V Martel

Micrometeorite bombardment accounts for almost 30,000 tons of material entering Earth's atmosphere each year. Though most of the material evaporates during entry or is lost at sea or falls on the land unnoticed, thousands of micrometeorites have been collected successfully from deep-sea sediments, from the snow and ice of the polar caps, and now from a water well at the South Pole.

If you think it's cold where you live, consider this cool little story about ice...Antarctic ice...studded with minuscule grains from the cosmos. Researchers are studying extraterrestrial materials that are particles and spherules less than a millimeter in size but whose combined mass accounts for about 1,000 tons of new stuff added to Earth yearly. A micrometeorite is generally defined as a tiny meteorite larger than 50 micrometers but smaller than a millimeter. Micrometeorites that have either partially or completely melted when plunging through Earth's atmosphere are called cosmic spherules.

Just as the Antarctic blue ice serves as an ideal collector of meteorites, it also preserves micrometeorites and cosmic spherules that land on the surface and are subsequently incorporated into ice layers.

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